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Compared to the determination of exercise thresholds based on systemic changes in blood lactate concentrations or gas exchange data, the determination of breakpoints based on muscle oxygen saturation offers a valid alternative to provide specific information on muscle-derived thresholds. Our study explored the profiles and timing of the second muscle oxygenation threshold (MOT2) in different muscles. Twenty-six cyclists and triathletes (15 male: age = 23 ± 7 years, height = 178 ± 5 cm, body mass = 70.2 ± 5.3 kg; 11 female: age = 22 ± 4 years, height = 164 ± 4 cm, body mass = 58.3 ± 8.1 kg) performed a graded exercise test (GXT), on a cycle ergometer. Power output, blood lactate concentration, heart rate, rating of perceived exertion, skinfolds and muscle oxygen saturation were registered in five muscles (vastus lateralis, biceps femoris, gastrocnemius medialis, tibialis anterior and triceps brachii) and percentage at which MOT2 occurred for each muscle was determinated using the Exponential Dmax. The results of Statistical Parametric Mapping and ANOVA showed that, although muscle oxygenation displayed different profiles in each muscle during a GXT, MOT2 occurred at a similar percentage of the GXT in each muscle (77% biceps femoris, 75% tibalis anterior, 76% gastrocnemius medialis and 72% vastus lateralis) and it was similar that systemic threshold (73% of the GXT). In conclusion, this study showed different profiles of muscle oxygen saturation in different muscles, but without notable differences in the timing for MOT2 and concordance with systemic threshold. Finally, we suggest the analysis of the whole signal and not to simplify it to a breakpoint., (© 2024. The Author(s).)

Significance: Near-infrared spectroscopy (NIRS) measurement is a widely used technique to measure muscle oxygenation. A knowledge of the reproducibility of NIRS measurements is essential for the correct interpretation of data., Aim: Our aim was to test the reproducibility and sex differences of NIRS measurements during brachial artery occlusion in healthy participants., Approach: An NIRS device was used to measure muscle oxygenation and microvascular function during a 5 min brachial occlusion. Muscle oxygen consumption (mVO 2 ) and tissue saturation index (TSI%) were used. The occlusion test was performed three times on separate days for males (n = 13, 28 ± 8 years) and females (n = 13, 29 ± 7 years)., Results: During the occlusion phase, the reproducibility of mVO 2 was excellent (intraclass correlation; ICC = 0.90). During the reperfusion phase, the maximal change in TSI% revealed the best reproducibility (ICC = 0.77). There were no sex differences in reproducibility. Male participants had higher muscle oxygenation during occlusion (mVO 2 , 0.054 ± 0.010 vs. 0.038 ± 0.012 mLO 2 /min/100 g, p = 0.001, male and female, respectively). There were no sex differences during the reperfusion phase., Conclusion: The reproducibility of NIRS to measure muscle oxygenation and microvascular function during circulation occlusion and reperfusion is good to excellent. Muscle oxygen capacity measured during occlusion is higher in males compared to females, and there are no sex differences in microvascular function during the reperfusion phase., (© 2024 The Authors. Clinical Physiology and Functional Imaging published by John Wiley & Sons Ltd on behalf of Scandinavian Society of Clinical Physiology and Nuclear Medicine.)

Introduction: Wearable near-infrared spectroscopy (NIRS) can be used during dynamic exercise to reflect the balance of muscle oxygen delivery and uptake. This study describes the behaviour and reliability of postexercise reoxygenation with NIRS as a function of exercise intensity at four muscle sites during an incremental cycling test. We discuss physiological components of faster and slower reoxygenation kinetics in the context of sport science and clinical applications. We hypothesised that reoxygenation would be slower at higher intensity, and that locomotor muscles would be faster than accessory muscles. We quantified test-retest reliability and agreement for each site., Methods: Twenty-one trained cyclists performed two trials of an incremental cycling protocol with 5-min work stages and 1-min rest between stages. NIRS was recorded from the locomotor vastus lateralis and rectus femoris muscles, and accessory lumbar paraspinal and lateral deltoid muscles. Reoxygenation time course was analysed as the half-recovery time (HRT) from the end of work to half of the peak reoxygenation amplitude during rest. Coefficient of variability (CV) between participants, standard error of the measurement (SEM) within participants, and intraclass correlation coefficient (ICC) for test-retest reliability were evaluated at 50%, 75%, and 100% peak workloads. A linear mixed-effects model was used to compare differences between workloads and muscle sites., Results: HRT was slower with increasing workload in the VL, RF, and PS, but not DL. VL had the fastest reoxygenation (lowest HRT) across muscle sites at all workloads (HRT = 8, 12, 17 s at 50%, 75%, 100% workload, respectively). VL also had the greatest reliability and agreement. HRT was sequentially slower between muscle sites in the order of VL < RF < PS < DL, and reliability was lower than for the VL., Discussion: This study highlights the potential for using wearable NIRS on multiple muscle sites during exercise. Reoxygenation kinetics differ between local muscle sites with increasing intensity. Moderate-to-good reliability in the VL support its increasing use in sport science and clinical applications. Lower reliability in other muscle sites suggest they are not appropriate to be used alone, but may add information when combined to better reflect systemic intensity and fatigue during exercise at different intensities., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Arnold, Yogev, Nelson, van Hooff and Koehle.)

Introduction: This study investigates the comparative efficacy of neuromodulation therapy using the EXOPULSE Mollii Suit and a structured exercise program in pain modulation and muscle oxygenation in Fibromyalgia patients. Methods: A randomized, crossover, longitudinal, and experimental study design was employed, involving 10 female Fibromyalgia patients. Participants were subjected to two distinct treatment modalities: neuromodulation therapy with the EXOPULSE Mollii Suit and a strength-based High-Intensity Interval Training (HIIT) exercise program, each conducted over 16 sessions. Outcome measures included pain severity, assessed using the Numeric Rating Scale (NRS), and muscle oxygenation variables measured via Near-Infrared Spectroscopy (NIRS). Results: Both interventions demonstrated significant reductions in NRS scores and improvements in muscle oxygenation. However, the exercise program yielded more pronounced long term basal adaptations in muscle oxygenation compared to the neuromodulation therapy. Discussion: The findings underscore the potential of integrating non-pharmacological treatments, particularly structured exercise programs, in managing Fibromyalgia. While neuromodulation therapy presents a viable alternative, the exercise regimen's capacity to induce basal muscle oxygenation adaptations suggests its superiority in addressing the complex symptoms of Fibromyalgia. Furthermore, these therapeutic approaches may enhance patients' vocational values and employability opportunities by improving their functional capabilities and overall quality of life., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Rubio-Zarapuz, Apolo-Arenas, Tornero-Aguilera, Parraca and Clemente-Suárez.)

Endothelial dysfunction decreases exercise limb blood flow (BF) and muscle oxygenation. Acute L-Citrulline supplementation (CIT) improves muscle tissue oxygen saturation index (TSI) and deoxygenated hemoglobin (HHb) during exercise. Although CIT improves endothelial function (flow-mediated dilation [FMD]) in hypertensive women, the impact of CIT on exercise BF and muscle oxygenation (TSI) and extraction (HHb) are unknown. We examined the effects of CIT (10 g/day) and a placebo for 4 weeks on blood pressure (BP), arterial vasodilation (FMD, BF, and vascular conductance [VC]), and forearm muscle oxygenation (TSI and HHb) at rest and during exercise in 22 hypertensive postmenopausal women. Compared to the placebo, CIT significantly ( p < 0.05) increased FMD (Δ-0.7 ± 0.6% vs. Δ1.6 ± 0.7%) and reduced aortic systolic BP (Δ3 ± 5 vs. Δ-4 ± 6 mmHg) at rest and improved exercise BF (Δ17 ± 12 vs. Δ48 ± 16 mL/min), VC (Δ-21 ± 9 vs. Δ41 ± 14 mL/mmHg/min), TSI (Δ-0.84 ± 0.58% vs. Δ1.61 ± 0.46%), and HHb (Δ1.03 ± 0.69 vs. Δ-2.76 ± 0.77 μM). Exercise BF and VC were positively correlated with improved FMD and TSI during exercise (all p < 0.05). CIT improved exercise artery vasodilation and muscle oxygenation via increased endothelial function in hypertensive postmenopausal women.

Purpose:  Peripheral responses might be important in handcycling, given the involvement of small muscles compared to other exercise modalities. Therefore, the goal of this study was to compare changes in muscle oxygen saturation (∆SmO 2 ) and deoxyhemoglobin level (∆[HHb]) between different efforts and muscles., Methods:  Handcyclists participated in a Wingate, a maximal incremental test and a 20-min time-trial (TT). Oxygen uptake (VO 2 ) as well as ∆SmO 2 , ∆[HHb], deoxygenation and reoxygenation rates in the triceps brachii (TB), biceps brachii (BB), anterior deltoid (AD) and extensor carpi radialis brevis (ER) were measured., Results:  ER ∆[HHb]max was 37% greater in the incremental test than in the Wingate (ES = 0.392, P = 0.031). TT mean power (W/kg) was associated with BB ∆SmO 2 min measured in the incremental test (r = -0.998 [-1.190, -0.806], P = 0.002) and in the Wingate (r = -0.994 [-1.327, -0.661], P = 0.006). MAP (W/kg) was associated with Wingate BB ∆SmO 2 min (r = -0.983 [-0.999, -0.839], P = 0.003), and Wingate peak (r = 0.649 [0.379, 0.895], P = 0.008) and mean power (W/kg) (r = 0.925 [0.752, 0.972], P = 0.003) was associated with right handgrip force. The strongest physiological predictor for TT performance was BB ∆SmO 2 min in the incremental test (P = 0.002, r 2  = 0.993, SEE 0.016 W/kg), Wingate BB ∆SmO 2 min for MAP (P = 0.003, r 2  = 0.956, SEE 0.058 W/kg) and right handgrip force for Wingate peak power (P = 0.005, r 2  = 0.856, SEE 0.551 W/kg)., Conclusion:  Peripheral aerobic responses (muscle oxygenation) were predictive of handcycling performance., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

In the recent past, practical blood flow restriction (pBFR) using non-pneumatic, usually elastic cuffs has been established as a cost-effective alternative to traditional blood flow restriction (BFR) using pneumatic cuffs, especially for training in large groups. This study investigated whether low-load resistance exercise with perceptually primed pBFR using an elastic knee wrap is suitable to induce similar motor performance fatigue as well as physiological and perceptual responses compared to traditional BFR using a pneumatic nylon cuff in males and females. In a randomized, counterbalanced cross-over study, 30 healthy subjects performed 4 sets (30-15-15-15 repetitions) of unilateral knee extensions at 20% of their one-repetition-maximum. In the pBFR condition, each individual was perceptually primed to a BFR pressure corresponding to 60% of their arterial occlusion pressure. Before and after exercise, maximal voluntary torque, maximal muscle activity, and cuff pressure-induced discomfort were assessed. Moreover, physiological (i.e., muscle activity, muscle oxygenation) and perceptual responses (i.e., effort and exercise-induced leg muscle pain) were recorded during exercise. Moderate correlations with no differences between pBFR and BFR were found regarding the decline in maximal voluntary torque and maximal muscle activity. Furthermore, no to very strong correlations between conditions, with no differences, were observed for muscle activity, muscle oxygenation, and perceptual responses during exercise sets. However, cuff pressure-induced discomfort was lower in the pBFR compared to the BFR condition. These results indicate that low-load resistance exercise combined with perceptually primed pBFR is a convenient and less discomfort inducing alternative to traditional BFR. This is especially relevant for BFR training with people who have a low cuff-induced discomfort tolerance., (© Journal of Sports Science and Medicine.)

Purpose: Portable near-infrared spectroscopy devices allow measurements of muscle oxygen saturation (SmO 2 ) in real time and non-invasively. To use NIRS for typical applications including intensity control and load monitoring, the day-to-day variability needs to be known to interpret changes confidently. This study investigates the absolute and relative test-retest reliability of the Moxy Monitor and investigates side differences of SmO 2 at the vastus lateralis muscle of both legs in cyclists., Methods: Twelve trained cyclists and triathletes completed 3 incremental step tests with 5 min step duration starting at 1.0 W/kg with an increase of 0.5 W/kg separated by 2-7 days. SmO 2 was averaged over the last minute of each stage. For all power outputs, the intra-class coefficient (ICC), the standard error of measurement (SEM) and the minimal detectable change (MDC) were calculated. Dominant and non-dominant leg SmO 2 were compared using a three-factor ANOVA and limits of agreement (LoA)., Results: ANOVA showed no significant systematic differences between trials and side. For both legs and all intensities, the ICC ranged from 0.79 to 0.92, the SEM from 5 to 9% SmO 2 and the MDC from 14 to 18% SmO 2 . The bias and LoA between both legs were -2.0% ± 19.9% SmO 2 ., Conclusion: Relative reliability of SmO 2 was numerically good to excellent according to current standards. However, it depends on the specific analytical goal whether the test-retest reliability is deemed sufficient. Wide LoA indicate side differences in muscle oxygenation during exercise unexplained by leg dominance., (© 2024. The Author(s).)

Long-term hyperglycemia in individuals with type 2 diabetes (T2D) can detrimentally impact pulmonary function and muscle oxygenation. As a result, these factors can impede the body's adaptation to physical exertion. We aimed to evaluate the oxygen pathway during maximal exercise among overweight/obese individuals with type 2 diabetes free from complications, in comparison with a group of matched overweight/obese individuals without diabetes, specifically concentrating on the effects on pulmonary function and muscle oxygenation. Fifteen overweight/obese adults with type 2 diabetes [glycated hemoglobin (HbA1c) = 8.3 ± 1.2%] and 15 matched overweight/obese adults without diabetes underwent pre- and post exercise lung function assessment. A maximal incremental exercise test was conducted, monitoring muscle oxygenation using near-infrared spectroscopy and collecting arterial blood gas samples. Both groups exhibited normal lung volumes at rest and after exercise. Spirometric lung function did not significantly differ pre- and post exercise in either group. During maximal exercise, the type 2 diabetes group showed significantly lower augmentation in total hemoglobin and deoxygenated hemoglobin compared with the control group. Despite comparable usual physical activity levels and comparable heart rates at exhaustion, the type 2 diabetes group had a lower peak oxygen consumption than controls. No significant differences were found in arterial blood gas analyses ([Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text]) between the groups. Individuals with type 2 diabetes free from complications displayed normal pulmonary function at rest and post exercise. However, impaired skeletal muscle oxygenation during exercise, resulting from reduced limb blood volume and altered muscle deoxygenation, may contribute to the lower V̇o 2peak observed in this population. NEW & NOTEWORTHY Individuals with type 2 diabetes free from micro- and macrovascular complications have normal resting pulmonary function, but their V̇o 2peak is impaired due to poor skeletal muscle oxygenation during exercise. Tailoring exercise regimes for this population should prioritize interventions aimed at enhancing muscle oxygenation and blood flow improvement.

The study aimed to calculate training intensity and load using muscle oxygen saturation (SmO 2 ) during two differentiated physical tasks. 29 university athletes participated in a 40-m Maximal Shuttle Run Test (MST, 10 × 40-m with 30 s recovery between sprints) and a 3000-m time trial run. Distance and time were used to calculate external load (EL). Internal load indicators were calculated based on percentage of maximum heart rate (%HR MAX ) and SmO 2 variables: muscle oxygen extraction (∇%SmO 2 ) and the cardio-muscle oxygen index (CMOI) was also provided by relating ∇%SmO2 ÷ %HR MAX , and the training load were calculated as the product of speed (m/min × IL) and the efficiency index [Eff index (m/min ÷ IL)]. A student t test was applied based on Bayesian factor analysis. As expected, EL differed in the 40-m MST (331 ± 22.8) vs. 3000-m trials (222 ± 56.8) [BF 10 = 6.25e +6 ; p = <0.001]. Likewise, IL showed higher values in 40-m MST (39.20 ± 15.44) vs. 3000-m (30.51 ± 8.67) in CMOI: [BF 10 = 1.70; p = 0.039]. Training load was greater in 40-m MST (85.77 ± 27.40) vs. 3000-m (15.55 ± 6.77) [(m/min × ∇%SmO 2 ): BF 10 = 12.5; p = 0.003] and 40-m MST (129.27 ± 49.44) vs. 3000-m (70.63 ± 32.98) [(m/min × CMOI): BF 10 = 169.6; p = <0.001]. Also, the Eff index was higher in 40-m MST (10.19 ± 4.17) vs. 3000-m (6.06 ± 2.21) [(m/min × ∇%SmO 2 ): BF 10 = 137.03; p = <0.001] and 40-m MST (9.69 ± 4.11) vs. 3000-m (7.55 ± 1.87) [(m/min × CMOI): BF 10 = 1.86; p = 0.035]. This study demonstrates calculations of training intensity and load based on SmO 2 as an internal load indicator along with speed as an external load indicator during two differentiated exercises.

Objectives: The purpose of this study was to compare physiological responses to myofascial release (MFR) and passive limb movement (PLM)., Design: Nineteen (23 ± 2.6yrs) adults (10 men and 9 women) completed two experiments on separate days: MFR and PLM. Participation included collecting ultrasound images, blood pressure, and heart rate (HR) as well as performing a vascular occlusion test (VOT). The VOT assessed muscle tissue oxygenation (StO 2 ) with near-infrared spectroscopy. Experiments consisted of moving the upper limb to release subtle barriers of resistance in the muscle/fascia (MFR) and passive, assisted range of motion (PLM)., Results: There was a significantly (p = 0.012) greater decrease in HR following MFR (-7.3 ± 5.2 BPM) than PLM (-1.3 ± 0.9 BPM). There was an equivalent change in brachial blood flow (-17.3 ± 23.0 vs. -11.9 ± 14.9 mL min -1 ; p = 0.37) and vascular conductance (-19.3 ± 31.1 vs. -12.4 ± 15.3 mL min -1  mmHg -1 ; p = 0.38). Microvascular responses differed between the experiments such that MFR exhibited greater area under the curve (AUC, 1503 ± 499.1%∙s -1 vs. 1203 ± 411.1%∙s -1 ; p = 0.021) and time to maximum StO 2 (40.0 ± 8.4s vs. 35.8 ± 7.3s; p = 0.009)., Conclusions: As evidenced by HR, MFR induced greater parasympathetic activity than PLM. The greater AUC and time to StO 2max following MFR suggested a spillover effect to induce prolonged hyper-saturation. These results may be of interest to those investigating possible MFR-related rehabilitative benefits., Competing Interests: Declaration of competing interest None., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

This study investigated whether the improved performance observed with maximal self-paced single-leg (SL), compared with double-leg (DL) cycling, is associated with enhanced femoral blood flow and/or altered tissue oxygenation. The hyperaemic response to exercise was assessed in younger and older athletes. Power output was measured in 12 older (65 ± 4 y) and 12 younger (35 ± 5 y) endurance-trained individuals performing 2 x 3 min maximal self-paced exercise using SL and DL cycling. Blood flow (BF) in the femoral artery was assessed using Doppler ultrasound and muscle oxygenation was measured using near-infrared spectroscopy on the vastus lateralis. SL cycling elicited a greater power output (295 ± 83 vs 265 ± 70 W, P < 0.001) and peak femoral BF (1749.1 ± 533.3 vs 1329.7 ± 391.7 ml/min, P < 0.001) compared with DL cycling. Older individuals had a lower peak BF in response to exercise (1355.4 ± 385.8 vs 1765.2 ± 559.6 ml/min, P = 0.019) compared with younger individuals. Peak BF in response to exercise was correlated with power output during SL (r = 0.655, P = 0.002) and DL (r = 0.666, P = 0.001) cycling. The greater exercise performance during SL compared with DL cycling may be partly explained by a greater hyperaemic response when reducing active muscle mass. Despite regular endurance training, older athletes had a lower femoral BF in response to maximal self-paced exercise compared with younger athletes., (© Journal of Sports Science and Medicine.)

This study aimed to compare the intensity of deoxygenated haemoglobin concentration ([HHb]) and tissue saturation index (TSI) breakpoints ([HHb]-BP and TSI-BP) with maximal lactate steady state (MLSS) and critical power (CP), and to describe their association with 2000-m rowing ergometer performance. Fourteen male rowers performed on a rowing ergometer: I) a discontinuous incremental test with 3-min stages (INC 3 ); II) a continuous incremental test with 1-min stages (INC 1 ); III) constant workload tests to determine MLSS; and IV) performance tests of 500 m, 1000 m, 2000 m and 6000 m to determine CP.CP (257 ± 39 W; 3.79 ± 4.1 L · min -1 ) was higher than [HHb]-BP 3 (205 ± 26 W; 3.48 ± 2.9 L · min -1 ), [HHb]-BP 1 (207 ± 27 W; 3.27 ± 3.2 L · min -1 ), and TSI-BP 3 (218 ± 31 W; 3.51 ± 3.0 L · min -1 ), but not higher than TSI-BP 1 (222 ± 34 W; 3.43 ± 3.2 L · min -1 ). MLSS (187 ± 26 W; 3.33 ± 3.2 L · min -1 ) was lower than TSI-BP 3 and TSI-BP 1 for power output, but not different in any comparison for ⩒O 2 . The limits of agreement for power output and ⩒O 2 suggest poor agreement among these thresholds. The low level of agreement compromises the use of [HHb]-BP and TSI-BP for estimating MLSS and CP; therefore, these thresholds should not be considered interchangeable., Competing Interests: The authors declare no conflict of interest., (Copyright © Biology of Sport 2024.)

Background: Phosphocreatine dynamics provide the gold standard evaluation of in-vivo mitochondrial function and is tightly coupled with oxygen availability. Low mitochondrial oxidative capacity has been associated with health issues and low exercise performance., Methods: To evaluate the relationship between near-infrared spectroscopy-based muscle oxygen dynamics and magnetic resonance spectroscopy-based energy-rich phosphates, a systematic review of the literature related to muscle oxygen dynamics and energy-rich phosphates was conducted. PRISMA guidelines were followed to perform a comprehensive and systematic search of four databases on 02-11-2021 (PubMed, MEDLINE, Scopus and Web of Science). Beforehand pre-registration with the Open Science Framework was performed. Studies had to include healthy humans aged 18-55, measures related to NIRS-based muscle oxygen measures in combination with energy-rich phosphates. Exclusion criteria were clinical populations, laboratory animals, acutely injured subjects, data that only assessed oxygen dynamics or energy-rich phosphates, or grey literature. The Effective Public Health Practice Project Quality Assessment Tool was used to assess methodological quality, and data extraction was presented in a table., Results: Out of 1483 records, 28 were eligible. All included studies were rated moderate. The studies suggest muscle oxygen dynamics could indicate energy-rich phosphates under appropriate protocol settings., Conclusion: Arterial occlusion and exercise intensity might be important factors to control if NIRS application should be used to examine energetics. However, more research needs to be conducted without arterial occlusion and with high-intensity exercises to support the applicability of NIRS and provide an agreement level in the concurrent course of muscle oxygen kinetics and muscle energetics., Trial Registration: https://osf.io/py32n/ ., Key Points: 1. NIRS derived measures of muscle oxygenation agree with gold-standard measures of high energy phosphates when assessed in an appropriate protocol setting. 2. At rest when applying the AO protocol, in the absence of muscle activity, an initial disjunction between the NIRS signal and high energy phosphates can been seen, suggesting a cascading relationship. 3. During exercise and recovery a disruption of oxygen delivery is required to provide the appropriate setting for evaluation through either an AO protocol or high intensity contractions., (© 2024. The Author(s).)

Thermogenesis is well understood, but the relationships between cold water immersion (CWI), the post-CWI rewarming and the associated physiological changes are not. This study investigated muscle and systemic oxygenation, cardiorespiratory and hemodynamic responses, and gastrointestinal temperature during and after CWI. 21 healthy men completed randomly 2 protocols. Both protocols consisted of a 48 minutes heating cycling exercise followed by 3 recovery periods (R1-R3), but they differed in R2. R1 lasted 20 minutes in a passive semi-seated position on a physiotherapy table at ambient room temperature. Depending on the protocol, R2 lasted 15 minutes at either ambient condition (R2&#95;AMB) or in a CWI condition at 10°C up to the iliac crest (R2&#95;CWI). R3 lasted 40 minutes at AMB while favoring rewarming after R2&#95;CWI. This was followed by 10 minutes of cycling. Compared to R2&#95;AMB, R2&#95;CWI ended at higher V ˙ O 2 in the non-immersed body part due to thermogenesis (7.16(2.15) vs. 4.83(1.62) ml.min -1 .kg -1 ) and lower femoral artery blood flow (475(165) vs. 704(257) ml.min -1 ) (p < 0.001). Only after CWI, R3 showed a progressive decrease in vastus and gastrocnemius medialis O 2 saturation, significant after 34 minutes ( p  < 0.001). As blood flow did not differ from the AMB protocol, this indicated local thermogenesis in the immersed part of the body. After CWI, a lower gastrointestinal temperature on resumption of cycling compared to AMB (36.31(0.45) vs. 37.30(0.49) °C, p  < 0.001) indicated incomplete muscle thermogenesis. In conclusion, the rewarming period after CWI was non-linear and metabolically costly. Immersion and rewarming should be considered as a continuum rather than separate events., Competing Interests: No potential conflict of interest was reported by the author(s)., (© 2024 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.)

The oxygen partial pressure within the interstitial space (PO 2 is; mmHg) provides the driving force for oxygen diffusion into the myocyte thereby supporting oxidative phosphorylation. We tested the hypothesis that potentiation of the nitric oxide pathway with sildenafil (phosphodiesterase type 5 inhibitor) would enhance PO 2 is during muscle metabolic transitions, thereby slowing PO 2 is on- and accelerating PO 2 is off-kinetics. The rat spinotrapezius muscle (n = 17) was exposed for PO 2 is measurements via phosphorescence quenching under control (CON), low-dose sildenafil (1 mg/kg i.a., SIL1) and high-dose sildenafil (7 mg/kg i.a., SIL7). Data were collected at rest and during submaximal twitch contractions (1 Hz, 4-6 V, 3 min) and recovery (3 min). Mean arterial blood pressure (MAP; mmHg) was reduced with both SIL1 (pre:132 ± 5; post:99 ± 5) and SIL7 (pre:111 ± 6; post:99 ± 4) (p < 0.05). SIL7 elevated resting PO 2 is (18.4 ± 1.1) relative to both CON (15.7 ± 0.7) and SIL1 (15.2 ± 0.7) (p < 0.05). In addition, SIL7 increased end-recovery PO 2 is (17.7 ± 1.6) compared to CON (12.8 ± 0.9) and SIL1 (13.4 ± 0.8) (p < 0.05). The overall PO 2 is response during recovery (i.e., area under the PO 2 is curve) was greater in SIL7 (4107 ± 444) compared to CON (3493 ± 222) and SIL1 (3114 ± 205 mmHg s) (p < 0.05). Contrary to our hypothesis, there was no impact of acute SIL (1 or 7 mg/kg) on the speed of the PO 2 is response during contractions or recovery (p > 0.05). However, sildenafil lowered MAP and improved skeletal muscle interstitial oxygenation in healthy rats. Specifically, SIL7 enhanced PO 2 is at rest and during recovery from submaximal muscle contractions. Potentiation of the nitric oxide pathway with sildenafil enhances microvascular blood-myocyte O 2 transport and is expected to improve repeated bouts of contractile activity., Competing Interests: Declaration of competing interest No conflicts of interest, financial or otherwise, are declared by the authors., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Purpose: Cranberries have the highest polyphenol and antioxidant capacity among fruits and vegetables and may protect against exercise-induced free radical production, consequently improving performance. This study aimed to investigate the effect of polyphenol-rich cranberry extract (CE) on time-trial performance and lactate response following exercise., Methods: A total of 14 trained runners were tested at i) baseline, ii) 2 h following an acute CE dose (0.7 g/kg of body mass), and iii) 4 weeks after daily supplement consumption (0.3 g/kg of body mass). At each time point, runners performed a 1500-m race followed by a 400-m race where the live vastus lateralis oxygenation changes were determined by near-infrared spectroscopy and blood lactate was measured at rest and 1 and 3 min after each trial. The Shapiro-Wilk test and repeated-measures analysis of variance were used to establish significance (P &lt;0.05)., Results: Cranberry supplementation over 28 d improved aerobic performance during the 1500-m time trial, whereas the acute dose had no effect. More specifically, muscle reoxygenation rates were significantly faster after 28 d compared to baseline (P = 0.04; η² = 0.29), and a trend towards slower deoxygenation rate was observed (P = 0.13; η² = 0.20). Chronic CE consumption also buffered the post-exercise lactate response for the 400-m race (P = 0.01; η² = 0.27), while no effects were seen for the longer race., Conclusion: Our results suggest that cranberry supplementation may have ergogenic effects, as it improves physiological markers of performance during short- and long-distance running.

This study aimed to assess the physiological responses to repeated running exercise performed at supramaximal intensity and with end-expiratory breath holding (EEBH) up to the breaking point. Eight male runners participated in two running testing sessions on a motorized treadmill. In the first session, participants performed two sets of 8 repetitions at 125% of maximal aerobic velocity and with maximum EEBH. Each repetition started at the onset of EEBH and ended at its release. In the second session, participants replicated the same procedure, but with unrestricted breathing (URB). The change in cerebral and muscle oxygenation (Δ[Hb diff ]), total haemoglobin concentration (Δ[THb]) and muscle reoxygenation were continuously assessed. End-tidal oxygen (PETO 2 ) and carbon dioxide pressure (PETCO 2 ), arterial oxygen saturation (SpO 2 ) and heart rate (HR) were also measured throughout exercise.On average, EEBH was maintained for 10.1 ± 1 s. At the breaking point of EEBH, PETO 2 decreased to 54.1 ± 8 mmHg, whereas PETCO 2 increased to 74.8 ± 3.1 mmHg. At the end of repetitions, SpO 2 (nadir values 74.9 ± 5.0 vs. 95.7 ± 0.8%) and HR were lower with EEBH than with URB. Cerebral and muscle Δ[Hb diff ] were also lower with EEBH, whereas this condition induced higher cerebral and muscle Δ[THb] and greater muscle reoxygenation. This study showed that performing repeated bouts of supramaximal running exercises with EEBH up to the breaking point induced a fall in arterial, cerebral and muscle oxygenation compared with the URB condition. These phenomena were accompanied by increases in regional blood volume likely resulting from compensatory vasodilation to preserve oxygen delivery to the brain and muscles., Competing Interests: The authors declare no conflict of interest., (Copyright: © Academy of Physical Education in Katowice.)

Background: Peripheral muscle fractional tissue oxygen extraction (pFTOE) represents the relative extraction of oxygen from the arterial to venous compartment, providing information about dynamic changes of oxygen delivery and oxygen consumption. The aim of the present study was to establish reference values of pFTOE during the first 24 h after birth in stable term and late preterm neonates., Methods: The present study is a post-hoc analysis of secondary outcome parameters of prospective observational studies. Only stable neonates without infection, asphyxia and any medical support were eligible for our analysis to obtain normal values. For measurements of peripheral muscle tissue oxygenation index (pTOI) during the first 24 h after birth in term and preterm neonates, the NIRO200/NIRO200NX was used. Arterial oxygen saturation (SpO 2 ) was obtained by pulse oximetry. pFTOE was calculated out of pTOI and SpO 2 : pFTOE = (SpO 2 -pTOI)/SpO 2 . Measurements of neonates were stratified into four groups according to their respective measurement time point (6 h periods) after birth. Term and preterm neonates were analyzed separately. Mean values of measurements during the first time period (0-6 h after birth) were compared to measurements of the following time periods (second = 7-12 h, third = 13-18 h, fourth = 19-24 h after birth)., Results: Two-hundred-fourty neonates (55 term and 185 late preterm neonates) had at least one peripheral muscle NIRS measurements within the first 24 h after birth. Mean gestational age and birth weight were 39.4 ± 1.1 weeks and 3360 (2860-3680)g in term neonates and 34.0 ± 1.4 weeks and 2060 (1750-2350)g in preterm neonates, respectively. In term neonates pFTOE was 0.264 (0.229-0.300), 0.228 (0.192-0.264), 0.237 (0.200-0.274) and 0.220 (0.186-0.254) in the first, second, third and fourth time period. In preterm neonates pFTOE was 0.229 (0.213-0.246), 0.225 (0.209-0.240), 0.226 (0.210-0.242) and 0.238 (0.222-0.255) in the first, second, third and fourth time period. pFTOE did not show any significant changes between the time periods, neither in term nor in preterm neonates., Conclusion: We provide reference values of pFTOE for stable term and late preterm neonates within the first 24 h after birth, which were stable when comparing four 6-h periods. These normal values are of great need for interpreting pFTOE in scientific context as well as for potential future clinical applications., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (© 2023 Wolfsberger, Höller, Baik-Schneditz, Schwaberger, Suppan, Mileder, Avian, Urlesberger and Pichler.)

Background: Practical blood flow restriction (pBFR) during exercise is a cost-saving alternative to traditional blood flow restriction using pneumatic cuffs, particularly when exercising in a group setting. Depending on the pBFR technique, several factors (e.g., cuff width, limb circumference) have already been shown to be of importance when applying the pBFR pressure. Given that elastic cuffs are often used for pBFR, the cuff stiffness might be an additional influencing factor. Therefore, the present study compared the acute effects of three elastic cuffs with identical width but different stiffness (high stiffness (HS), medium stiffness (MS), and low stiffness (LS)) on hemodynamic measures and perceived cuff pressure at rest., Methods: In a randomized, counter-balanced cross-over study, 36 young and normotensive participants completed three experimental trials. After a 10-min rest period in supine position, the cuff was loosely and proximally applied to the right upper arm. Following baseline data recording, the cuff was successively tightened in 10%-increments with respect to the limb circumference (%overlap) until arterial blood flow was occluded. At baseline and during each %overlap, systolic peak blood flow velocity of the brachial artery, rating of perceived cuff pressure, as well as muscle oxygen saturation and total hemoglobin concentration of the biceps brachii muscle were recorded., Results: The %overlap required to occlude arterial blood flow was different between the three cuffs (HS: 30.9 ± 3.8%, MS: 43.9 ± 6.1%, LS: 54.5 ± 8.3%). Furthermore, at 30% overlap, systolic peak blood flow velocity was lower when applying the HS (9.0 ± 10.9 cm∙s - 1 ) compared to MS (48.9 ± 21.9 cm∙s - 1 ) and LS cuff (62.9 ± 19.1 cm∙s - 1 ). Rating of perceived cuff pressure at 30% overlap was higher when using the HS (6.5 ± 1.5 arbitrary unit (a.u.)) compared to MS (5.1 ± 1.4 a.u.) and LS cuff (4.9 ± 1.5 a.u.) with no difference between the MS and LS cuff. However, muscle oxygen saturation and total hemoglobin concentration were not different between the three cuffs., Conclusions: The present study revealed that the cuff stiffness influenced blood flow velocity and arterial occlusion pressure. Therefore, cuff stiffness seems an important factor for the application of pBFR., (© 2023. BioMed Central Ltd., part of Springer Nature.)

The goal of this study was to investigate the effects of photobiomodulation therapy (PBMT) on performance, oxygen uptake (VO 2 ) kinetics, and lower limb muscle oxygenation during three successive time-to-exhaustions (TTEs) in cyclists. This was a double-blind, randomized, crossover, placebo-controlled trial study. Sixteen cyclists (~23 years) with a cycling training volume of ~460 km/week volunteered for this study. In the first session, cyclists performed a maximal incremental test to determine maximal oxygen uptake and maximal power output (PO MAX ). In the following sessions, cyclists performed three consecutive TTEs at PO MAX . Before each test, PBMT (135 J/thigh) or a placebo (PLA) was applied to both thighs. VO 2 amplitude, O 2 deficit, time delay, oxyhemoglobin (O 2 Hb), deoxyhemoglobin (HHb), and total hemoglobin (tHb) were measured during tests on the right vastus lateralis. The PBMT applied before three successive TTE increased performance of the first and second TTE (~10-12%) tests, speed of VO 2 and HHb kinetics during the first test, and increased peripheral muscle oxygenation (increase in HHb and tHb) in the first and second exhaustion tests. However, the PBMT effects were attenuated in the third TTE, as performance and all the other outcomes were similar to the ones from the PLA intervention. In summary, PBMT application increased the first and second successive TTEs, speed of VO 2, and muscle oxygenation.

Purpose: It has been hypothesized that sports injury risk is explained by muscle metabolism. The objective was to evaluate the muscle oxygen saturation slopes (ΔSmO 2 slopes) and muscle oxygenation asymmetry (MO 2 Asy) at rest and to study their associations with injuries during the pre-season. Methods: A total of 16 male and 10 female footballers participated in this study. Injuries were diagnosed and classified by level of severity during the pre-season. The workload was also evaluated using the rate of perceived exertion × training time, from which the accumulated loads. The SmO 2 was measured at rest in the gastrocnemius muscle using the arterial occlusion method in the dominant and non-dominant legs. The repeated measures ANOVA, relative risk, and binary logistic regression were applied to assess the probability of injury with SmO 2 and workload. Results: Higher MO 2 Asy and ΔSmO 2 Slope 2 were found among footballer who suffered high-severity injuries and those who presented no injuries. In addition, an MO 2 Asy greater than 15% and an increase in accumulated load were variables that explained a greater probability of injury. Conclusion: This study presents the new concept of muscle oxygenation asymmetry in sports science and its possible application in injury prevention through the measurement of SmO 2 at rest.

We investigated the relationship between muscle microvascular responses during reactive hyperemia as assessed using near-infrared spectroscopy (NIRS) with changes in skeletal muscle oxygen saturation during exercise. Thirty young untrained adults (M/W: 20/10; 23 ± 5 years) completed a maximal cycling exercise test to determine exercise intensities performed on a subsequent visit separated by seven days. At the second visit, post-occlusive reactive hyperemia was measured as changes in NIRS-derived tissue saturation index (TSI) at the left vastus lateralis muscle. Variables of interest included desaturation magnitude, resaturation rate, resaturation half-time, and hyperemic area under the curve. Afterwards, two 4-minute bouts of moderate intensity cycling followed by one bout of severe intensity cycling to fatigue took place while TSI was measured at the vastus lateralis muscle. TSI was averaged across the last 60-s of each moderate intensity bout then averaged together for analysis, and at 60-s into severe exercise. The change in TSI (∆TSI) during exercise is expressed relative to a 20 W cycling baseline. On average, the ΔTSI was -3.4 ± 2.4 % and -7.2 ± 2.8 % during moderate and severe intensity cycling, respectively. Resaturation half-time was correlated with the ΔTSI during moderate (r = -0.42, P = 0.01) and severe (r = -0.53, P = 0.002) intensity exercise. No other reactive hyperemia variable was found to correlate with ΔTSI. These results indicate that resaturation half-time during reactive hyperemia represents a resting muscle microvascular measure that associates with the degree of skeletal muscle desaturation during exercise in young adults., Competing Interests: Declaration of competing interest The authors (JD, AF, and JG) have no conflicts of interest, financial or otherwise, to declare., (Copyright © 2023 Elsevier Inc. All rights reserved.)

This study investigated the acute performance, physiological, and perceptual changes during repeated sprint exercise (RSE) under normobaric hypoxia and with blood flow restriction (BFR). Fourteen active males completed standardized RSE (6 × 10 s cycling sprints with 30 s passive rest) in three randomized conditions: under normobaric hypoxia (F i O 2 ∼ 14.4%, HYP), normoxia (F i O 2 ∼ 20.9%, SHAM), and with BFR (40% arterial occlusion pressure). The percentage decrement score of power output (S dec ) was used to quantify motor performance fatigue. During RSE, muscle oxygenation (total and oxygenated hemoglobin) and activity of the right quadriceps were measured. Perceived motor fatigue, physical strain, affective valence, and arousal were queried after each sprint. Blood lactate concentration (BLC) and peripheral oxygenation (S p O 2 ) were measured before and after RSE. S dec was greater in HYP and BFR compared to SHAM (p ≤ 0.008). BFR decreased mean power output (p < 0.001) and muscle activity (p = 0.027) compared to SHAM. Decrease in muscle oxygenated hemoglobin was higher in BFR during each rest (p ≤ 0.005) and in HYP during rest 4 (p = 0.006) compared to SHAM. HYP increased BLC and decreased S p O 2 compared to BFR (p < 0.001) and SHAM (p = 0.002). There were no differences between conditions for any rating scale (p ≥ 0.060). HYP and BFR increased motor performance fatigue but with different physiological responses, whereas perceptual responses were unaffected during RSE., Competing Interests: Declaration of Competing Interest The authors declare no conflicts of interest., (Copyright © 2023 Elsevier Inc. All rights reserved.)

This study aimed to elucidate whether muscle blood flow restriction during maximal exercise is associated with alterations in hemodynamics, cerebral oxygenation, cerebral activation, and deterioration of exercise performance in male participants. Thirteen healthy males, cyclists (age 33 ± 2 yrs., body mass: 78.6 ± 2.5 kg, and body mass index: 25.57 ± 0.91 kg·m -1 ), performed a maximal incremental exercise test on a bicycle ergometer in two experimental conditions: (a) with muscle blood flow restriction through the application of thigh cuffs inflated at 120 mmHg (with cuffs, WC) and (b) without restriction (no cuffs, NC). Exercise performance significantly deteriorated with muscle blood flow restriction, as evidenced by the reductions in V˙O 2max (-17 ± 2%, p < 0.001), peak power output (-28 ± 2%, p < 0.001), and time to exhaustion (-28 ± 2%, p < 0.001). Muscle oxygenated hemoglobin (Δ[O 2 Hb]) during exercise declined more in the NC condition ( p < 0.01); however, at exhaustion, the magnitude of muscle oxygenation and muscle deoxygenation were similar between conditions ( p > 0.05). At maximal effort, lower cerebral deoxygenated hemoglobin (Δ[HHb]) and cerebral total hemoglobin (Δ[THb]) were observed in WC ( p < 0.001), accompanied by a lower cardiac output, heart rate, and stroke volume vs. the NC condition ( p < 0.01), whereas systolic blood pressure, rating of perceived exertion, and cerebral activation (as assessed by electroencephalography (EEG) activity) were similar ( p > 0.05) between conditions at task failure, despite marked differences in exercise duration, maximal aerobic power output, and V˙O 2max . In conclusion, in trained cyclists, muscle blood flow restriction during an incremental cycling exercise test significantly limited exercise performance. Exercise intolerance with muscle blood flow restriction was mainly associated with attenuated cardiac responses, despite cerebral activation reaching similar maximal levels as without muscle blood flow restriction.

Muscle glycogen state and carbohydrate (CHO) supplementation before and during exercise may impact responses to high-intensity interval training (HIIT). This study determined cardiorespiratory, substrate metabolism, muscle oxygenation, and performance when completing HIIT with or without CHO supplementation in a muscle glycogen depleted state. On two occasions, in a cross-over design, eight male cyclists performed a glycogen depletion protocol prior to HIIT during which either a 6% CHO drink (60 g.hr -1 ) or placebo (%CHO, PLA) was consumed. HIIT consisted of 5 × 2 min at 80% peak power output (PPO), 3 × 10-min bouts of steady-state (SS) cycling (50, 55, 60% PPO), and a time-to-exhaustion (TTE) test. There was no difference in SS [Formula: see text], HR, substrate oxidation and gross efficiency (GE %) between CHO and PLA conditions. A faster rate of muscle reoxygenation (%. s -1 ) existed in PLA after the 1st (Δ - 0.23 ± 0.22, d = 0.58, P < 0.05) and 3rd HIIT intervals (Δ - 0.34 ± 0.25, d = 1.02, P < 0.05). TTE was greater in CHO (7.1 ± 5.4 min) than PLA (2.5 ± 2.3 min, d = 0.98, P < 0.05). CHO consumption before and during exercise under reduced muscle glycogen conditions did not suppress fat oxidation, suggesting a strong regulatory role of muscle glycogen on substrate metabolism. However, CHO ingestion provided a performance benefit under intense exercise conditions commenced with reduced muscle glycogen. More research is needed to understand the significance of altered muscle oxygenation patterns during exercise., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Purpose: This study investigated the physical fitness and oxygen uptake kinetics ([Formula: see text]) along with the exercise-onset O 2 delivery (heart rate kinetics, τHR; changes in normalized deoxyhemoglobin/[Formula: see text] ratio, Δ[HHb]/[Formula: see text]) adaptations of individuals with different physical activity (PA) backgrounds responding to 4 weeks of high-intensity interval training (HIIT), and the possible effects of skeletal muscle mass (SMM) on training-induced adaptations., Methods: Twenty subjects (10 high-PA level, HIIT-H; 10 moderate-PA level, HIIT-M) engaged in 4 weeks of treadmill HIIT. Ramp-incremental (RI) test and step-transitions to moderate-intensity exercise were performed. Cardiorespiratory fitness, body composition, muscle oxygenation status, VO 2 and HR kinetics were assessed at baseline and post-training., Results: HIIT improved fitness status for HIIT-H ([Formula: see text], + 0.26 ± 0.07 L/min; SMM, + 0.66 ± 0.70 kg; body fat, - 1.52 ± 1.93 kg; [Formula: see text], - 7.11 ± 1.05 s, p < 0.05) and HIIT-M ([Formula: see text], 0.24 ± 0.07 L/min, SMM, + 0.58 ± 0.61 kg; body fat, - 1.64 ± 1.37 kg; [Formula: see text], - 5.48 ± 1.05 s, p < 0.05) except for visceral fat area (p = 0.293) without between-group differences (p > 0.05). Oxygenated and deoxygenated hemoglobin amplitude during the RI test increased for both groups (p < 0.05) except for total hemoglobin (p = 0.179). The Δ[HHb]/[Formula: see text] overshoot was attenuated for both groups (p < 0.05) but only eliminated in HIIT-H (1.05 ± 0.14 to 0.92 ± 0.11), and no change was observed in τHR (p = 0.144). Linear mixed-effect models presented positive effects of SMM on absolute [Formula: see text] (p < 0.001) and ΔHHb (p = 0.034)., Conclusion: Four weeks of HIIT promoted positive adaptations in physical fitness and [Formula: see text] kinetics, with the peripheral adaptations attributing to the observed improvements. The training effects are similar between groups suggesting that HIIT is effective for reaching higher physical fitness levels., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Rationale & Objective: Previous studies in chronic kidney disease (CKD) showed that vascular dysfunction in different circulatory beds progressively deteriorates with worsening CKD severity. This study evaluated muscle oxygenation and microvascular reactivity at rest, during an occlusion-reperfusion maneuver, and during exercise in patients with different stages of CKD versus controls., Study Design: Observational controlled study., Setting & Participants: 90 participants (18 per CKD stage 2, 3a, 3b, and 4, as well as 18 controls)., Predictor: CKD stage., Outcome: The primary outcome was muscle oxygenation at rest. Secondary outcomes were muscle oxygenation during occlusion-reperfusion and exercise, and muscle microvascular reactivity (hyperemic response)., Analytical Approach: Continuous measurement of muscle oxygenation [tissue saturation index (TSI)] using near-infrared spectroscopy at rest, during occlusion-reperfusion, and during a 3-minute handgrip exercise (at 35% of maximal voluntary contraction). Aortic pulse wave velocity and carotid intima-media thickness were also recorded., Results: Resting muscle oxygenation did not differ across the study groups (controls: 64.3% ± 2.9%; CKD stage 2: 63.8% ± 4.2%; CKD stage 3a: 64.1% ± 4.1%; CKD stage 3b: 62.3% ± 3.3%; CKD stage 4: 62.7% ± 4.3%; P=0.6). During occlusion, no significant differences among groups were detected in the TSI occlusion magnitude and TSI occlusion slope. However, during reperfusion the maximum TSI value was significantly lower in groups of patients with more advanced CKD stages compared with controls, as was the hyperemic response (controls: 11.2%±3.7%; CKD stage 2: 8.3%±4.6%; CKD stage 3: 7.8%±5.5%; CKD stage 3b: 7.3%±4.4%; CKD stage 4: 7.2%±3.3%; P=0.04). During the handgrip exercise, the average decline in TSI was marginally lower in patients with CKD than controls, but no significant differences were detected across CKD stages., Limitations: Moderate sample size, cross-sectional evaluation., Conclusions: Although no differences were observed in muscle oxygenation at rest or during occlusion, the microvascular hyperemic response during reperfusion was significantly impaired in CKD and was most prominent in more advanced CKD stages. This impaired ability of microvasculature to respond to stimuli may be a crucial component of the adverse vascular profile of patients with CKD and may contribute to exercise intolerance., Plain-Language Summary: Previous studies in chronic kidney disease (CKD) have shown that vascular dysfunction in different circulatory beds progressively deteriorates with CKD severity. This study evaluated muscle oxygenation and microvascular reactivity at rest, during an occlusion-reperfusion maneuver, and during exercise in patients with nondialysis CKD versus controls, as well as across different CKD stages. It showed that the microvascular hyperemic response after an arterial occlusion was significantly impaired in CKD and was worst in patients with more advanced CKD. No significant differences were detected in skeletal muscle oxygenation or muscle oxidative capacity at rest or during the handgrip exercise when comparing patients with CKD with controls or comparing across CKD stages. The impaired ability of microvasculature to respond to stimuli may be a component of the adverse vascular profile of patients with CKD and may contribute to exercise intolerance., (Copyright © 2023 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.)

In the present study, it was evaluated whether microencapsulated cocoa supplementation could attenuate endothelial dysfunction caused by eccentric exercise in healthy subjects. Thirteen volunteers were enrolled in this double-blind, placebo-controlled, crossover study. Flow-mediated dilatation (FMD), blood flow and muscle O 2 saturation (StO 2 ) were evaluated by ultrasound and near-infrared spectroscopy (NIRS), respectively, before and after microencapsulated cocoa supplementation. The eccentric exercise was performed after microencapsulated cocoa supplementation to generate vascular dysfunction. Eccentric exercise significantly reduced FMD in the PLA condition, but cocoa attenuated this exercise effect. No significant effect was observed on muscle StO 2 and blood flow after eccentric exercise and nutritional supplementation. In conclusion, the present study showed that a single dose of microencapsulated cocoa ingestion attenuated FMD-induced eccentric exercise. These findings suggest that a single dose of microencapsulated cocoa may be an alternative nutritional strategy to attenuate vascular dysfunction induced by eccentric exercise in healthy individuals.

Purpose: Resistance training (RT) is an effective countermeasure to combat physical deconditioning whereby localized hypoxia within the limb increases metabolic stress eliciting muscle adaptation. The current study sought to examine the influence of gravity on muscle oxygenation (SmO 2 ) alongside vascular hemodynamic responses., Methods: In twelve young healthy adults, an ischemic occlusion test and seven minutes of low-intensity rhythmic plantarflexion exercise were used alongside superficial femoral blood flow and calf near-infrared spectroscopy to assess the microvascular vasodilator response, conduit artery flow-mediated dilation, exercise-induced hyperemia, and SmO 2 with the leg positioned above or below the heart in a randomized order., Results: The microvascular vasodilator response, assessed by peak blood flow (798 ± 231 mL/min vs. 1348 ± 290 mL/min; p < 0.001) and reperfusion slope 10 s of SmO 2 after cuff deflation (0.75 ± 0.45%.s-1 vs.2.40 ± 0.94%.s-1; p < 0.001), was attenuated with the leg above the heart. This caused a blunted dilatation of the superficial femoral artery (3.0 ± 2.4% vs. 5.2 ± 2.1%; p = 0.008). Meanwhile, blood flow area under the curve was comparable (above the heart: 445 ± 147 mL vs. below the heart: 474 ± 118 mL; p = 0.55) in both leg positions. During rhythmic exercise, the increase in femoral blood flow was lower in the leg up position (above the heart: 201 ± 94% vs. below the heart: 292 ± 114%; p = 0.001) and contributed to a lower SmO 2 (above the heart: 41 ± 18% vs. below the heart 67 ± 5%; p < 0.001)., Conclusion: Positioning the leg above the heart results in attenuated peak vascular dilator response and exercise-induced hyperemia that coincided with a lower SmO 2 during low-intensity plantarflexion exercise., (© 2023. The Author(s).)

Use of muscle oxygen saturation (SmO 2 ) has been validated as a performance factor during incremental exercise with portable near-infrared stereoscopy (NIRS) technology. However, there is little knowledge about the use of SmO 2 to identify training zones. The objective of this study was to evaluate the metabolic zones by SmO 2 : maximum lipid oxidation zone (Fatmax), ventilatory thresholds (VT1 and VT2) and maximum aerobic power (MAP) during a graded exercise test (GXT). Forty trained cyclists and triathletes performed a GXT. Output power (W), heart rate (HR), oxygen consumption (VO 2 ), energy expenditure (kcal/min) and SmO 2 were measured. Data were analysed using the ANOVA test, ROC curves and multiple linear regressions. Significance was established at p ≤ 0.05. SmO 2 decreases were observed from baseline (LB) to Fatmax ( Δ = -16% p < 0.05), Fatmax to VT1 ( Δ = -16% p < 0.05) and VT1 to VT2 ( Δ = -45% p < 0.01). Furthermore, SmO 2 together with weight, HR and output power have the ability to predict VO 2 and energy expenditure by 89% and 90%, respectively. We conclude that VO 2 and energy expenditure values can be approximated using SmO 2 together with other physiological parameters and SmO 2 measurements can be a complementary parameter to discriminate aerobic workload and anaerobic workload in athletes., Competing Interests: The authors did not received any funding for this work and have no conflicts of interests to declare., (Copyright © Biology of Sport 2023.)

Objective: To compare peripheral muscle oxygenation levels and the prevalence of psychological stress in adolescents with and without temporomandibular disorder (TMD)., Methods: A cross-sectional study was performed with adolescents submitted into two groups: those diagnosed with TMD (DG) and control (CG). Muscle oxygenation was measured by near-infrared spectroscopy in the masseter and upper trapezius muscles. Symptoms of stress were assessed by Lipp's Stress Symptom Inventory for Adults or Child Stress Scale. A Student t-test was used for intergroup comparisons and association between categorical variables by chi-square test, phi coefficient of correlation, odds ratio, and two-way ANOVA., Results: Fifty-three adolescents were evaluated and a significant reduction was observed in the oxyhemoglobin level in the masseter muscle at rest (p = 0.04) and contraction (p = 0.02). A greater total hemoglobin level was found in the upper trapezius muscle at rest in DG (p = 0.03), with a significant difference in the tissue saturation index during contraction (p = 0.05) intergroup. Individuals in the DG were 4.523 times more likely to exhibit signs and symptoms of stress than in CG., Conclusion: Adolescents from DG showed reduced masseter oxyhemoglobin values at rest and during contraction and showed more signs and symptoms of stress than healthy controls. In the upper trapezius, DG showed higher values of total circulating hemoglobin, essential for greater blood flow and efficient maximum voluntary contraction., Clinical Relevance: Changes in tissue oxygenation and stress in adolescents with TMD prompted the earlier treatment of this population to prevent disease progression into adulthood., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

As differential physiological responses to hypoxic exercise between adults and children remain poorly understood, we aimed to comprehensively characterise cardiorespiratory and muscle oxygenation responses to submaximal and maximal exercise in normobaric hypoxia between the two groups. Following familiarisation, fifteen children (Age = 9 ± 1 years) and fifteen adults (Age = 22 ± 2 years) completed two graded cycling exercise sessions to exhaustion in a randomized and single-blind manner in normoxia (NOR; F i O 2 = 20.9) and normobaric hypoxia (HYP; F i O 2 = 13.0) exercises conditions. Age-specific workload increments were 25 W·3 min -1 for children and 40 W·3 min -1 for adults. Gas exchange and vastus lateralis oxygenation parameters were measured continuously via metabolic cart and near-infrared spectroscopy, respectively. Hypoxia provoked significant decreases in maximal power output P MAX (children = 29%; adults 16% (F = 39.3; p < 0.01)) and power output at the gas exchange threshold (children = 10%; adults:18% (F = 8.08; p = 0.01)) in both groups. Comparable changes were noted in most respiratory and gas exchange parameters at similar power outputs between groups. Children, however, demonstrated, lower P ET CO 2 throughout the test at similar power outputs and during the maintenance of V˙CO 2 at the maximal power output. These data indicate that, while most cardiorespiratory responses to acute hypoxic exercise are comparable between children and adults, there exist age-related differential responses in select respiratory and muscle oxygenation parameters.

Near-infrared spectroscopy (NIRS) quantifies muscle oxygenation (SmO 2 ) during exercise. Muscle oxygenation response to self-paced, severe-intensity cycling remains unclear. Observing SmO 2 can provide cycling professionals with the ability to assess muscular response, helping optimize decision-making. We aimed to describe the effect of self-paced severe intensity bouts on SmO 2 , measured noninvasively by a wearable NIRS sensor on the vastus lateralis (VL) muscle, and examine its reliability. We hypothesized a greater desaturation response with each bout, whereas, between trials, good reliability would be observed. Fourteen recreationally trained, and trained cyclists completed a ramp test to determine the power output (PO) at the respiratory compensation point (RCP). Athletes completed two subsequent visits of 50-minute sessions that included four severe-intensity bouts done at 5% above RCP PO. Muscle oxygenation in the VL was monitored using a wearable NIRS device. Measures included mean PO, heart-rate (HR), cadence, and SmO 2 at bout onset, during work (work SmO 2 ), and Δ SmO 2 . The bouts were compared using a one-way repeated measures ANOVA. For significant differences, a Fisher's least square difference post-hoc analysis was used. A two-way repeated measures ANOVA was used using trial and bout as main factors. Intraclass correlations (ICC) were used to quantify relative reliability for mean work, and standard error of the measurement (SEM) was used to quantify absolute agreement of mean work SmO 2 . Both PO and cadence showed no effect of bout or trial. Heart-rate at bout 2 (168 ± 8 bpm) and 4 (170 ± 7 bpm) were higher than bout 1 (160 ± 6 bpm). Onset SmO 2 (%) response significantly increased in the final two bouts of the session. Mean work SmO 2 increased across bouts, with the highest value displayed in bout 4 (36 ± 22%). Δ SmO 2 showed a smaller desaturation response during bout 4 (27 ± 10%) compared to bout 3 (31 ± 10%). Mean work SmO 2 ICC showed good reliability (ICC = 0.87), and SEM was 12% (CI 9-15%). We concluded that a non-invasive, affordable, wearable NIRS sensor demonstrated the heterogeneous muscle oxygenation response during severe intensity cycling bouts with good reliability in trained cyclists., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (© 2023 Yogev, Arnold, Nelson, Clarke, Guenette, Sporer and Koehle.)

Skeletal muscle perfusion and oxygenation are commonly evaluated using Doppler ultrasound and near-infrared spectroscopy (NIRS) techniques. However, a recently developed magnetic resonance imaging (MRI) sequence, termed PIVOT, permits the simultaneous collection of skeletal muscle perfusion and T2* (an index of skeletal muscle oxygenation)., Purpose: To determine the level of agreement between PIVOT, Doppler ultrasound, and NIRS-based assessments of skeletal muscle perfusion and oxygenation., Methods: Twelve healthy volunteers (8 females, 25 ± 3 years, 170 ± 11 cm, 71.5 ± 8.0 kg) performed six total reactive hyperemia protocols. During three of these reactive hyperemia protocols, Tissue Saturation Index (TSI) and oxygenated hemoglobin (O 2 Hb) were recorded from the medial gastrocnemius (MG) and tibialis anterior (TA), and blood flow velocity was recorded from the popliteal artery (BFv pop ) via Doppler Ultrasound. The other three trials were performed inside the bore of a 3 T MRI scanner, and the PIVOT sequence was used to assess perfusion (PIVOT perf ) and oxygenation (T2*) of the medial gastrocnemius and tibialis anterior muscles. Positive incremental areas under the curve (iAUC) and times to peak (TTP) were calculated for each variable, and the level of agreement between collection methods was evaluated via Bland-Altman analyses and Spearman's Rho correlation analyses., Results: The only significant bivariate relationships observed were between the T2* vs. TSI iAUC and PIVOT perf vs. BFv pop values recorded from the MG. Significant mean differences were observed for all comparisons (all P ≤ 0.038), and significant proportional biases were observed for the PIVOT perf vs. tHb TTP (R 2  = 0.848, P < 0.001) and T2* vs. TSI TTP comparisons in the TA (R 2  = 0.488, P = 0.011), and the PIVOT perf vs. BFv pop iAUC (R 2  = 0.477, P = 0.013) and time to peak (R 2  = 0.851, P < 0.001) comparisons in the MG., Conclusions: Our findings suggest that the PIVOT technique has, at best, a moderate level of agreement with Doppler ultrasound and NIRS assessment methods and is subject to significant proportional bias. These findings do not challenge the accuracy of either measurement technique but instead reflect differences in the vascular compartments, sampling volumes, and parameters being evaluated., Competing Interests: Declaration of Competing Interest The authors have no conflicts of interest to report., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Purpose: The present study investigated the effects of adding heat stress to repeated-sprint training in hypoxia on performance and physiological adaptations in well-trained athletes., Methods: Sixteen canoe/kayak sprinters conducted 2 weeks of repeated-sprint training consisting of three sets of 5 × 10 s sprints with 20 s active recovery periods under conditions of either normobaric hypoxia (RSH, FiO 2 : 14.5%, ambient temperature: 18 ℃, n = 8) or combined heat and normobaric hypoxia (RSHH, FiO 2 : 14.5%, ambient temperature: 38 ℃, n = 8). Before and after training, the 10 × 10 s repeated-sprint ability (RSA) test and 500 m time trial were performed on a canoe/kayak ergometer., Results: Peak and average power outputs during the RSA test were significantly improved after training in both RSH (peak power: + 21.5 ± 4.6%, P < 0.001; average power: + 12.5 ± 1.9%, P < 0.001) and RSHH groups (peak power: + 18.8 ± 6.6%, P = 0.005; average power: + 10.9 ± 6.8%, P = 0.030). Indirect variables of skeletal muscle oxygen extraction (deoxygenated hemoglobin) and blood perfusion (total hemoglobin) during the RSA test were significantly increased after training in the RSH group (P = 0.041 and P = 0.034, respectively) but not in the RSHH group. In addition, finish time during the 500 m time trial was significantly shortened after the training only in the RSH group (RSH: - 3.9 ± 0.8%, P = 0.005; RSHH: - 3.1 ± 1.4%, P = 0.078)., Conclusion: Adding heat stress to RSH does not enhance performance improvement and may partially mask muscle tissue adaptation., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Near-infrared spectroscopy (NIRS) is widely used in sports science research, despite the limited reliability of available data. The aim of the present study was to assess the reliability of NIRS with and without compression tights. Thirteen healthy active males, (age 21.5 ± 2.7 years, body mass 82.1 ± 11.2 kg, BMI 24.6 ± 3.2 kg·m -2 ) completed four trials (two control trials and two trials using compression tights) over a 28-day period. During each trial, participants completed 20 min each of laying supine, sitting, walking (4 km·h -1 ), jogging, and sitting following the jogging. An NIRS device was attached to the muscle belly of the vastus lateralis and gastrocnemius and recorded tissue saturation index (TSI), muscle oxygenation, and muscle deoxygenation. Systematic bias and 95% limits of agreement (LOA) and coefficient of variation (CV) were used to report reliability measures for each activity type. For TSI, systematic bias (LOA) at the gastrocnemius during the control and tights trial ranged from -0.4 to 1.7% (4.4 to 10.3%) and -1.9 to 3.5% (8.1 to 12.0%), respectively. For the vastus lateralis, the systematic bias (LOA) for the control trial ranged from -2.4 to 1.0% (5.1 to 6.9%) and for the tights trial was -0.8 to 0.6% (7.0 to 9.5%). For TSI, the CV during the control trial ranged from 1.7 to 4.0% for the gastrocnemius and 1.9 to 2.6% for the vastus lateralis. During the tights trials, the CV ranged from 3.0 to 4.5% for the gastrocnemius and 2.6 to 3.5% for the vastus lateralis. The CV for muscle oxygenation during the control and tights trials for the gastrocnemius was 2.7 to 6.2% and 1.0 to 8.8% and for the vastus lateralis was 0.6 to 4.0% and 4.0 to 4.5%, respectively. The relative reliability was poorer in the tights trials, but if the aim was to detect a 5% difference in TSI, NIRS would be sufficiently reliable. However, the reliability of muscle oxygenation and deoxygenation varies considerably with activity type, and this should be considered when determining whether to employ NIRS in research studies.

Long periods of bed rest for elderly population, due to a femur fracture event, can cause a deterioration in the muscular capacity. Therefore, monitoring of the muscle oxidative capacity in this fragile population is necessary to define the muscular oxidative metabolism state before and after a rehabilitation period. The time-domain near-infrared spectroscopy (TD-NIRS) technique enables the absolute values to be calculated for hemodynamic parameters such as oxy- (O 2 Hb), deoxy- (HHb), total- (tHb) haemoglobin, and tissue oxygen saturation (SO 2 ) of the muscular tissue. In this work, we have characterized vastus lateralis muscle hemodynamics during a baseline period at two different time points: after the surgery (PRE) and after 15 days of rehabilitation (POST). The mean values for the absolute values of the hemodynamic parameters were: O 2 Hb&#95;PRE = 49.1 ± 14.1 μM; O 2 Hb&#95;POST = 47.1 ± 13.4 μM; HHb&#95;PRE = 28.3 ± 10.3 μM; HHb&#95;POST = 26.7 ± 9.9 μM; tHb&#95;PRE = 77.3 ± 23.6 μM; tHb&#95;POST = 73.8 ± 21.4 μM; SO 2 &#95;PRE = 63.9 ± 4.0% and SO 2 &#95;POST = 64.9 ± 5.6%. The hemodynamic parameters did not show significant differences at both group and single subject level. These results suggest that for this kind of population, the baseline of the hemodynamic parameters is not the best one to consider to assess the rehabilitation progresses in terms of muscular oxidative metabolism., (© 2023. The Author(s), under exclusive license to Springer Nature Switzerland AG.)

The aim of this study was to investigate the longitudinal relationship between the slopes of systemic and quadriceps muscle O 2 dynamics in subjects without attenuation point in deoxygenated hemoglobin concentration at vastus lateralis (AP deoxy-Hb@VL ) during high-intensity cycling. Seven young men without AP deoxy-Hb@VL performed ramp cycling exercise until exhaustion before and after 8 weeks, while continuing recreational physical activities throughout that period. Muscle O 2 saturation (SmO 2 ) and deoxy-Hb were monitored at the vastus lateralis (VL) and rectus femoris (RF) by near infrared spectroscopy oximetry during exercise. Cardiac output (CO) was also continuously assessed. During high-intensity exercise, at VL, a significantly steeper slope of deoxy-Hb was found after 8 weeks compared with before, while the slopes of deoxy-Hb at RF were not significantly changed. Though a decrease in the slope of CO after 8 weeks did not reach significance (p = 0.12), the change in the slope of CO was significantly related to the change in the slopes of deoxy-Hb at VL (r s  = -0.89, p < 0.01) and RF (r s  = -0.86, p < 0.05). Our data reinforces the idea that, in subjects without AP deoxy-Hb@VL , the slope of muscle deoxygenation at VL during high-intensity cycling exercise may partly be explained by systemic O 2 supply, rather than O 2 balance in other thigh muscles., (© 2023. The Author(s), under exclusive license to Springer Nature Switzerland AG.)

This study quantified performance and physiological responses during multi-set resistance exercise to failure at light versus moderate loads in normoxia and systemic hypoxia. On separate visits, fifteen resistance-trained adults performed barbell biceps curl exercise trials (6 sets to failure, 2 min rest between sets) in four separate randomised conditions; i.e. in normoxia at 380 m above sea level or systemic hypoxia at ∼3800 m simulated altitude (inspired oxygen fraction = 20.9% and 12.9%, respectively) combined with two different intensity levels (30% and 70% of 1 repetition maximal or 1RM). Muscle activation (root mean square value calculated from surface electromyography) and oxygenation (integrated-tissue saturation index derived from near-infrared spectroscopy) were monitored for the biceps brachii muscle. The total number of repetitions before failure at 30% 1RM (122 ± 5 vs . 131 ± 5; P  = 0.021), but not 70% 1RM (39 ± 1 vs . 41 ± 2; P  = 0.313), was lower in hypoxia compared to normoxia. Root mean square activity of the biceps brachii muscle was higher for 70% 1RM compared to 30% 1RM ( P  < 0.001), while the increase in muscle activation from the first to the last set ( P  < 0.001) occurred independently of altitude ( P  > 0.158). Deoxygenation and reoxygenation responses were higher under hypoxic versus normoxic conditions at 70% 1 RM ( P  = 0.013 and P  = 0.015) but not 30% 1RM ( P  = 0.528 and P  = 0.384). During upper-limb multi-set resistance exercise to failure, exposure to acute normobaric hypoxia negatively impacts performance at light, but not moderate, loads. Overall, external resistance has more profound effects on physiological strain than hypoxic exposure per se . Highlights The addition of acute systemic hypoxia negatively affects work performed at low, but not moderate, loads during upper-limb resistance exercise to failure.Hypoxic exposure, however, does not fundamentally alter muscle activation and oxygenation patterns.Muscle activation and oxygenation responses in turn are more largely influenced by load lifted.

The effects of sympathetic activity on vasoconstriction are dampened in active skeletal muscle during exercise, a phenomenon termed functional sympatholysis. Limited work has examined the influence of sex on the magnitude of sympatholysis or the test-retest reliability of measurements. In 16 women and 15 men, forearm blood flow (FBF; Doppler ultrasound), muscle oxygenation (near-infrared spectroscopy, NIRS), and beat-to-beat mean arterial pressure (MAP; photoplethysmography) were measured during lower-body negative pressure (LBNP; -20 mmHg) at rest and simultaneously during rhythmic handgrip exercise (30% maximum contraction). Measures were taken twice within the same visit (separated by 15 min) and repeated on a second visit. Forearm vascular conductance (FVC) was calculated as FBF/MAP. The magnitude of sympatholysis was calculated as the difference of LBNP-induced changes between handgrip and rest. LBNP decreased FBF (Δ-45 ± 15%), FVC (Δ-45 ± 16%), and muscle oxygenation (Δ-14 ± 11%); however, these responses were attenuated when LBNP was applied during rhythmic handgrip exercise (Δ-7 ± 9%, Δ-9 ± 10%, and Δ-6 ± 9%, respectively). The magnitude of sympatholysis was not different between men and women (FBF: 40 ± 16% vs. 35 ± 9%, P = 0.37; FVC: 38 ± 16% vs. 35 ± 11%, P = 0.53; muscle oxygenation: 5 ± 9% vs. 11 ± 10%, P = 0.11). Furthermore, sympatholysis measurements demonstrated good to excellent intraday (intraclass-correlation coefficients; ICC ≥ 0.85) and interday (ICC ≥ 0.72) test-retest reliability (all P ≤ 0.01) in both sexes. The coefficients of variation were larger with NIRS (68-91%) than with Doppler ultrasound (16%-22%) assessments of functional sympatholysis. Collectively, these findings demonstrate that assessments of functional sympatholysis are not impacted by biological sex and that Doppler ultrasound-derived measures of sympatholysis have better within-subject reliability than NIRS-derived measures in young healthy adults.

Background: Repetitive electrically-evoked muscle contractions lead to the early onset of muscle fatigue. This study assessed the relationship between muscle mechanomyography (%RMS-MMG) and tissue oxygen saturation (%TSI) in extensor carpi radialis (ECR) during electrically-evoked fatiguing exercise in individuals with tetraplegia., Methods: Skin-surface mechanomyography (MMG) and near-infrared spectroscopy (NIRS) sensors were placed on the ECR of seven individuals with tetraplegia. All participants performed repetitive electrically-evoked wrist extension to fatigue while their muscle MMG and NIRS responses were monitored against their power output (PO)., Findings: One out of seven participants showed no changes in %TSI throughout the repeated wrist FES-evoked contraction. The other six participants' %TSI was positively correlated with %PO before fatigue onset. At 50%PO peak , %TSI was negatively correlated (0.489) significantly with declining %PO as the ability of the muscle to take up oxygen became limited. The %RMS-MMG behaved analogously during pre and post-fatigue against declining %PO, whereby both displayed positive correlations of 0.443 and 0.214, respectively, (%RMS-MMG decreased) throughout the exercise session. Regression analysis revealed that %TSI was proportional to pre-fatigue and inversely proportional to %RMS-MMG during post-fatigue., Conclusion: The significant changes in muscle mechanomyography and tissue oxygenation correlations after 50%PO peak implied that the muscle contraction mechanical-and-physiological behavior association had been altered following FES-evoked fatigue., (© 2022 International Center for Artificial Organ and Transplantation (ICAOT) and Wiley Periodicals LLC.)

Breast cancer survivors (BCS) have a high prevalence of cardiovascular disease and low cardiorespiratory fitness (CRF). CRF is an important predictor of survival in BCS. However, the physiological factors that contribute to low CRF in BCS have not been completely elucidated. To assess differences in physiological factors (cardiac, pulmonary, muscle function) related to CRF between BCS and controls. Twenty-three BCS and 23 age-body mass index (BMI) matched controls underwent a peak cycling exercise test to determine CRF, with physiological factors measured at resting and at peak exercise. Cardiac hemodynamics (stroke volume [SV], SVindex, heart rate [HR], cardiac output [Formula: see text], and [Formula: see text]index) were evaluated using ultrasonography. Pulmonary function was evaluated using the oxygen uptake efficiency slope (OUES), ventilation to carbon dioxide production slope [Formula: see text] and breathing reserve at peak exercise (BR). Muscle oxygenation variables (oxygenated [HbO 2 ] deoxygenated [HHb] and total hemoglobin [Hb], and tissue oxygenation index [TSI]) were measured with near-infrared spectroscopy (NIRS). Both groups had similar CRF and similarly increased all hemodynamic variables (HR, SV, SVindex, [Formula: see text] and [Formula: see text]index) at peak exercise compared to resting (p < 0.001). BCS had higher overall HR and lower SVindex (group effect, p < 0.05). BCS had similar OUES, [Formula: see text] and BR compared to the controls. Both groups decreased TSI, and increased Hb and HHb similarly at peak exercise compared to resting (p < 0.001). Our data suggest BCS do not exhibit differences in cardiac, pulmonary, or muscle function at peak exercise compared to controls, when both groups have similar CRF and physical activity., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

The intensity of large muscle mass exercise declines at altitude due to reduced oxygen delivery to active muscles. The purpose of this investigation was to determine if the greater limb blood flow during single-leg cycling prevents the reduction in tissue oxygenation observed during traditional double-leg cycling in hypoxic conditions. Ten healthy individuals performed bouts of double and single-leg cycling (4, four-minute stages at 50−80% of their peak oxygen consumption) in hypoxic (15% inspired O2) and normoxic conditions. Heart rate, mean arterial pressure, femoral blood flow, lactate, oxygenated hemoglobin, total hemoglobin, and tissue saturation index in the vastus lateralis were recorded during cycling tests. Femoral blood flow (2846 ± 912 mL/min) and oxygenated hemoglobin (−2.98 ± 3.56 au) during single-leg cycling in hypoxia were greater than double-leg cycling in hypoxia (2429 ± 835 mL/min and −6.78 ± 3.22 au respectively, p ≤ 0.01). In addition, tissue saturation index was also reduced in the double-leg hypoxic condition (60.2 ± 3.1%) compared to double-leg normoxic (66.0 ± 2.4%, p = 0.008) and single-leg hypoxic (63.3 ± 3.2, p < 0.001) conditions. These data indicate that while at altitude, use of reduced muscle mass exercise can help offset the reduction in tissue oxygenation observed during larger muscle mass activities allowing athletes to exercise at greater limb/muscle specific intensities.

Although several studies have focused on the adaptations provided by inspiratory muscle (IM) training on physical demands, the warm-up or pre-activation (PA) of these muscles alone appears to generate positive effects on physiological responses and performance. This study aimed to understand the effects of inspiratory muscle pre-activation (IM PA ) on high-intensity running and passive recovery, as applied to active subjects. In an original and innovative investigation of the impacts of IM PA on high-intensity running, we proposed the identification of the interactions among physical characteristics, physiological responses and muscle oxygenation in more and less active muscle to a running exercise using a complex network model. For this, fifteen male subjects were submitted to all-out 30 s tethered running efforts preceded or not preceded by IM PA , composed of 2 × 15 repetitions (1 min interval between them) at 40% of the maximum individual inspiratory pressure using a respiratory exercise device. During running and recovery, we monitored the physiological responses (heart rate, blood lactate, oxygen saturation) and muscle oxygenation (in vastus lateralis and biceps brachii) by wearable near-infrared spectroscopy (NIRS). Thus, we investigated four scenarios: two in the tethered running exercise (with or without IM PA ) and two built into the recovery process (after the all-out 30 s), under the same conditions. Undirected weighted graphs were constructed, and four centrality metrics were analyzed (Degree, Betweenness, Eigenvector, and Pagerank). The IM PA (40% of the maximum inspiratory pressure) was effective in increasing the peak and mean relative running power, and the analysis of the complex networks advanced the interpretation of the effects of physiological adjustments related to the IM PA on exercise and recovery. Centrality metrics highlighted the nodes related to muscle oxygenation responses (in more and less active muscles) as significant to all scenarios, and systemic physiological responses mediated this impact, especially after IM PA application. Our results suggest that this respiratory strategy enhances exercise, recovery and the multidimensional approach to understanding the effects of physiological adjustments on these conditions.

Background and Objectives: Muscle blood flow is impeded during resistance exercise contractions, but immediately increases during recovery. The purpose of this study was to determine the impact of brief bouts of rest (2 s) between repetitions of resistance exercise on muscle blood flow and exercise tolerance. Materials and Methods: Ten healthy young adults performed single-leg knee extension resistance exercises with no rest between repetitions (i.e., continuous) and with 2 s of rest between each repetition (i.e., intermittent). Exercise tolerance was measured as the maximal power that could be sustained for 3 min (PSUS) and as the maximum number of repetitions (Reps80%) that could be performed at 80% one-repetition maximum (1RM). The leg blood flow, muscle oxygenation of the vastus lateralis and mean arterial pressure (MAP) were measured during various exercise trials. Alpha was set to p ≤ 0.05. Results: Leg blood flow was significantly greater, while vascular resistance and MAP were significantly less during intermittent compared with continuous resistance exercise at the same power outputs (p < 0.01). PSUS was significantly greater during intermittent than continuous resistance exercise (29.5 ± 2.1 vs. 21.7 ± 1.2 W, p = 0.01). Reps80% was also significantly greater during intermittent compared with continuous resistance exercise (26.5 ± 5.3 vs. 16.8 ± 2.1 repetitions, respectively; p = 0.02), potentially due to increased leg blood flow and muscle oxygen saturation during intermittent resistance exercise (p < 0.05). Conclusions: In conclusion, a brief rest between repetitions of resistance exercise effectively decreased vascular resistance, increased blood flow to the exercising muscle, and increased exercise tolerance to resistance exercise.

Purpose: Wearing compression garments is a commonly used intervention in sports to improve performance and facilitate recovery. Some evidence supports the use of forearm compression to improve muscle tissue oxygenation and enhance sports climbing performance. However, evidence is lacking for an effect of compression garments on hand grip strength and specific sports climbing performance. The purpose of this study was to evaluate the immediate effects of forearm compression sleeves on muscular strength and endurance of finger flexor muscles in sports climbers. Materials and Methods: This randomized crossover study included 24 sports climbers who performed one familiarization trial and three subsequent test trials while wearing compression forearm sleeves (COMP), non-compressive placebo forearm sleeves (PLAC), or no forearm sleeves (CON). Test trials consisted of three performance measurements (intermittent hand grip strength and endurance measurements, finger hang, and lap climbing) at intervals of at least 48 h in a randomized order. Muscle oxygenation during hand grip and finger hang measurements was assessed by near-infrared spectroscopy. The maximum blood lactate level, rate of perceived exertion, and forearm muscle pain were also determined directly after the lap climbing trials. Results: COMP resulted in higher changes in oxy[heme] and tissue oxygen saturation (StO 2 ) during the deoxygenation (oxy[heme]: COMP -10.7 ± 5.4, PLAC -6.7 ± 4.3, CON -6.9 ± 5.0 [μmol]; p = 0.014, η p 2 = 0.263; StO 2 : COMP -4.0 ± 2.2, PLAC -3.0 ± 1.4, CON -2.8 ± 1.8 [%]; p = 0.049, η p 2 = 0.194) and reoxygenation (oxy [heme]: COMP 10.2 ± 5.3, PLAC 6.0 ± 4.1, CON 6.3 ± 4.9 [μmol]; p = 0.011, η p 2 = 0.274; StO 2 : COMP 3.5 ± 1.9, PLAC 2.4 ± 1.2, CON 2.3 ± 1.9 [%]; p = 0.028, η p 2 = 0.225) phases of hand grip measurements, whereas total [heme] concentrations were not affected. No differences were detected between the conditions for the parameters of peak force and fatigue index in the hand grip, time to failure and hemodynamics in the finger hang, or performance-related parameters in the lap climbing measurements ( p ≤ 0.05). Conclusions: Forearm compression sleeves did not enhance hand grip strength and endurance, sports climbing performance parameters, physiological responses, or perceptual measures. However, they did result in slightly more pronounced changes of oxy [heme] and StO 2 in the deoxygenation and reoxygenation phases during the hand grip strength and endurance measurements., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Limmer, de Marées and Roth.)

The purpose of this study was to analyze the muscle oxygen saturation (SmO 2 ) of static and dynamic warm-up and assess their impact on athletic preparation. The acute effects of static and dynamic stretching on muscular and functional performance have been well established, with many studies highlighting physiological factors and performance markers (such as range of motion and flexibility). To date, no studies have analyzed the effects of dynamic stretching on muscle oxygenation. Twenty-three recreationally fit participants performed both static (SS) and dynamic stretching (DS) protocols targeting the rectus femoris muscle while the effects on SmO 2 were monitored using near-infrared spectroscopy (NIRS). SmO 2 levels after stretching were significantly ( p = 0.04; d = 2.21) enhanced with DS (62.8 ± 12.6%) compared to SS (55.1 ± 17.8%). The effect persisted for two minutes after stretching had ceased, which may have implications for exercise prescription.