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The results of this study suggest the cerebrovascular response between moderately endurance-trained males and females is comparable in spite of a higher arterial carbon dioxide and cardiac output in males compared with females during incremental aerobic exercise until volitional exhaustion. This could help in providing a better understanding of the key differences in cerebral blood flow regulation between males and females during aerobic exercise.

Purpose: In short-track speed skating, athletes need to possess specific physiological capabilities to perform explosive starts and to finish races with faster lap times than their opponents. Repeated-sprint training in hypoxia (RSH) can enhance repeated-sprint ability and high-intensity performance. This study aimed to evaluate the relationship between on- and off-ice performance indicators for training and testing purposes and how these are optimized with RSH in world-class short-track speed skaters including world and Olympic champions. Methods: RSH training was administered for 3 consecutive weeks, 3 times per week, at 3500 m of simulated altitude. Testing sessions (on-ice: 3-lap, 27-lap; off-ice: cycling incremental test, 7-s and 30-s Wingate) were performed immediately before and 2 and 4 weeks after RSH to determine the time course of decay. Results: On-ice top speed showed a small and possibly beneficial change of ∼0.9% for the women and large and almost certain ∼0.7% improvement for the men 2 weeks post-RSH. Cycling peak power showed a moderate and probable ∼5.4% improvement for the men 2 weeks after RSH. These adaptations reverted to baseline 4 weeks post-RSH. Wingate average power showed a small and possibly beneficial gain (∼3.4%) in performance 4 weeks post-RSH. Conclusion: Although scientific controls could not be added due to the extremely high caliber of these athletes and low sample size of the national team, this study suggests that cycling RSH can be added immediately after on-ice training and can transfer into meaningful improvements on the ice in both male and female skaters.

The present study aims to investigate the acute performance and physiological responses, with specific reference to muscle oxygenation, to ambient air temperature manipulation during repeated-sprint training in hypoxia (RSH). Thirteen male team-sport players completed one familiarisation and three experimental sessions at a simulated altitude of ∼3000 m (FIO2 0.144). Air temperatures utilised across the three experimental sessions were: 20°C, 35°C and 40°C (all 50% relative humidity). Participants performed 3 × 5 × 10-s maximal cycle sprints, with 20-s passive recovery between sprints, and 5 min active recovery between sets. There were no differences between conditions for cycling peak power, mean power, and total work (p>0.05). Peak core temperature (Tc) was not different between conditions (38.11±0.36°C). Vastus lateralis muscle deoxygenation during exercise and reoxygenation during recovery was of greater magnitude in 35°C and 40°C than 20°C (p 0.05). Exercise-induced increases in blood lactate concentration were higher in 35°C and 40°C than 20°C (p=0.010 and p=0.001, respectively). Integrating ambient temperatures up to 40°C into a typical RSH session had no detrimental effect on performance. Additionally, the augmented muscle oxygenation changes experienced during exercise and recovery in temperatures >35°C may indicate that the potency of RSH training is increased with additional heat. However, alterations to the training session may be required to generate a sufficient rise in Tc for heat training purposes.

The goal of this study was to assess the effects of repeated running bouts with end-expiratory breath holding (EEBH) up to the breaking point on muscle oxygenation. Eight male runners participated in three randomised sessions each including two exercises on a motorised treadmill. The first exercise consisted in performing 10–12 running bouts with EEBH of maximum duration either (separate sessions) at 60% (active recovery), 80% (passive recovery) or 100% (passive recovery) of the maximal aerobic velocity (MAV). Each repetition started at the onset of EEBH and ended at its release. In the second exercise of the session, subjects replicated the same procedure but with normal breathing (NB). Arterial oxygen saturation (SpO2), heart rate (HR) and the change in vastus lateralis muscle deoxy-haemoglobin/myoglobin (Δ[HHb/Mb]) and total haemoglobin/myoglobin (Δ[THb/Mb]) were continuously monitored throughout exercises. On average, the EEBHs were maintained for 10.1 ± 1.1 s, 13.2 ± 1.8 s and 12.2 ± 1.7 s during exercise at 60%, 80% and 100% of MAV, respectively. In the three exercise intensities, SpO2 (mean nadir values: 76.3 ± 2.5 vs 94.5 ± 2.5%) and HR were lower with EEBH than with NB at the end of the repetitions; whereas, the mean Δ[HHb/Mb] (12.6 ± 5.2 vs 7.7 ± 4.4 µm) and Δ[THb/Mb] (− 0.6 ± 2.3 vs 3.8 ± 2.6 µm) were, respectively, higher and lower with EEBH (p

To assess the performance change and physiological adaptations following nine sessions of short high-intensity interval training (HIIT) or sprint-interval training (SIT) in sprint kayakers. Twelve trained kayakers performed an incremental test and 3 time trials (200 m, 500 m and 1000 m) on a kayak ergometer. Oxygen consumption (VO2) and muscle oxygenation of the latissimus dorsi, biceps brachii, and vastus lateralis were measured. Athletes were then paired for sex and VO2max and randomized into a HIIT or a SIT training group, and performed nine training sessions before repeating the tests. Training improved performance in HIIT (200 m: + 3.8 ± 3.1%, p = 0.06; 500 m: + 2.1 ± 4.1%, p = 0.056; 1000 m: + 3.0 ± 4.6%, p = 0.13) but changes in performance remained within the smallest worthwhile change in SIT (200 m: + 0.8 ± 4.1%, p = 0.59; 500 m: + 0.5 ± 4.1%, p = 0.87; 1000 m: + 1.3 ± 4.6%, p = 0.57). In the 1000 m, training led to a greater deoxygenation in the biceps brachii and vastus lateralis in HIIT, and in the latissimus dorsi in SIT. In HIIT, the best predictors of improvements in 1000 m performance were increases in latissimus dorsi and vastus lateralis maximal deoxygenation. In a group of trained sprint kayakers, greater improvements in performance can be obtained with HIIT compared with SIT, for any distance. Training did not change VO2peak, but increased muscle maximal deoxygenation, suggesting both HIIT and SIT elicit peripheral adaptations. Performance improvement in the 1000 m was associated with increased maximal muscle deoxygenation, reinforcing the contribution of peripheral adaptations to performance in sprint kayaking.

To investigate within the one study potential molecular and cellular changes associated with mitochondrial biogenesis following 15 days of exposure to moderate hypoxia. Eight males underwent a muscle biopsy before and after 15 days of hypoxia exposure (FiO2 = 0.140–0.154; ~ 2500–3200 m) in a hypoxic hotel. Mitochondrial respiration, citrate synthase (CS) activity, and the content of genes and proteins associated with mitochondrial biogenesis were investigated. Our main findings were the absence of significant changes in the mean values of CS activity, mitochondrial respiration in permeabilised fibers, or the content of genes and proteins associated with mitochondrial biogenesis, after 15 days of moderate normobaric hypoxia. Our data provide evidence that 15 days of moderate normobaric hypoxia have negligible influence on skeletal muscle mitochondrial content and function, or genes and proteins content associated with mitochondrial biogenesis, in young recreationally active males. However, the increase in mitochondrial protease LON content after hypoxia exposure suggests the possibility of adaptations to optimise respiratory chain function under conditions of reduced O2 availability.

Context: Capsaicinoids and capsinoids (CAP) are natural substances found primarily in chili peppers and other spicy foods that agonize the transient receptor potential vanilloid-1 in the mouth, stomach, and small intestine. Several studies have shown CAP to be a potential antiobesity agent and to exhibit an analgesic effect in both rodents and humans. However, there is no scientific consensus about the effects of CAP on physical exercise performance and its physiological mechanisms of action. Purpose: This systematic review aimed to better elucidate the effects of CAP compounds as ergogenic aids and to discuss underlying mechanisms of action by which this supplement may potentially enhance endurance performance and muscular strength. Conclusions: Among 22 studies included in the review, 14 examined the effects of capsaicinoid or capsinoid compounds on endurance and resistance exercise performance in animals, with 9 studies showing benefits on performance. In humans, 8 studies were included: 3 demonstrated significant acute endurance benefits and 2 showed acute resistance exercise performance benefits compared with a placebo condition. Therefore, while more mechanistic studies are necessary to confirm these outcomes in humans, the available scientific literature appears to suggest that these compounds could be considered an effective nutritional strategy to improve exercise performance.

Background: The application of ischemic preconditioning (IPC) to resistance exercise has attracted some attention, owing to increases in muscle performance. However, there is still no consensus on the optimal occlusion pressure for this procedure. This study compared the acute effects of IPC with high and low pressure of occlusion on upper and lower limb maximal strength and heart rate variability in recreationally trained individuals. Methods: Sixteen recreationally trained men (25.3 ± 1.7 years; 78.4 ± 6.2 kg; 176.9 ± 5.4 cm; 25.1 ± 1.5 m2 kg−1) were thoroughly familiarized with one repetition maximum (1 RM) testing in the following exercises: bench press (BP), front latissimus pull-down (FLPD), and shoulder press (SP) for upper limbs, and leg press 45º (LP45), hack machine (HM), and Smith Squat (SS) for lower limbs. The 1 RM exercises were then randomly performed on three separate days: after a high pressure (220 mmHg, IPChigh) and a low pressure (20 mmHg, IPClow) IPC protocol and after no intervention (control, CON). Heart rate variability was also measured at rest, during and after the entire IPC protocol, and after the exercises. Results: Maximal strength was significantly (p < 0.05) higher in both IPChigh and IPClow compared with CON in all upper- and lower-limb exercises. There was no difference between the two experimental conditions. No significant differences were found in the comparison across the different experimental conditions for LFnu, HFnu, LF/HF ratio, and RMSSDms. Conclusions: IPC performed with both high and low pressures influenced heart rate variability, which may partly explain the maximal strength enhancement.

This study investigated the efficacy of ischemic preconditioning (IPC) on the recovery of maximal aerobic performance and physiological responses compared with commonly used techniques. Nine endurance athletes performed two 5-km cycling time trials (TT) interspersed by 45 minutes of recovery that included either IPC, active recovery (AR) or neuromuscular electrical stimulation (NMES) in a randomized crossover design. Performance, blood markers, arterial O2 saturation (SpO2), heart rate (HR), near-infrared spectroscopy-derived muscle oxygenation parameters and perceptual measures were recorded throughout TTs and recovery. Differences were analyzed using repeated-measures ANOVAs and Cohen’s effect size (ES). The decrement in chronometric performance from TT1 to TT2 was similar between recovery modalities (IPC: -6.1 sec, AR: -7.9 sec, NMES: -5.4 sec, p = 0.84, ES 0.05). The modalities induced similar increases in blood volume before the start of TT2 (IPC: 13.3%, AR: 14.6%, NMES: 15.0%, p = 0.79, ES 0.06) and similar changes in lactate concentration and pH. There were negligible differences between conditions in bicarbonate concentration, base excess of blood and total concentration of carbon dioxide, and no difference in SpO2, HR and muscle O2 extraction during exercise (all p > 0.05). We interpreted these findings to suggest that IPC is as effective as AR and NMES to enhance muscle blood volume, metabolic by-products clearance and maximal endurance performance. IPC could therefore complement the athlete’s toolbox to promote recovery.

Dong, L, Paradelo, D, Delorme, A, Oliveira, J, Parillo, B, Croteau, F, Romeas, T, Dube, E, Bieuzen, F, Billaut, F, and Berryman, N. Sport-specific agility and change of direction in water polo: The reliability and validity of two newly developed tests. J Strength Cond Res 35(12S): S111-S118, 2021-There is a gap in water-based agility testing that considers both the change-of-direction (COD) and perceptive-reactive components of agility. This study sought to develop easily implementable, sport-specific in-water agility tests for water polo and to verify the reliability and validity of these new tests: the in-water Stop and Go (SG) and Jump and Go (JG). Female water polo athletes at the Senior (n = 12, age = 22.1 ± 2.1 years), Junior (n = 19, age = 18.5 ± 1.0 years), and Youth (n = 11, age = 16.5 ± 0.8 years) national levels performed 3 trials of each of the SG, JG, and the existing Functional Test for Agility Performance (FTAP). Senior athletes performed an additional experimental session to assess reliability parameters. Relative reliability for agility and COD versions of the SG and JG was high or very high (intraclass correlation coefficient [ICC] = 0.76-0.95). For construct validity analyses, significant between-group differences for each of the new tests (p < 0.05) were found. In contrast, the FTAP was moderately reliable (ICC = 0.57) and was unsuccessful in discriminating between playing levels. Considering the favorable metrological properties of the SG and JG, their fidelity to in-game demands, and their accessible setups, these new tests represent viable options to implement at grassroots and elite levels for the assessment and training of water polo-specific agility.

The ergogenic effect of ischemic preconditioning (IPC) on endurance exercise performed in hypoxia remains debated and has never been investigated with successive exercise bouts. Therefore, we evaluated if IPC would provide immediate or delayed effects during two 5-km cycling time trials (TT) separated by ~1 h in hypoxia. In a counterbalanced randomized crossover design, 13 healthy males (27.5 ± 3.6 yr) performed two maximal cycling 5-km TT separated by ~1 h of recovery (TT1 25 min and TT2 2 h post-IPC/SHAM), preceded by IPC (3 × 5 min occlusion 220 mm Hg/reperfusion 0 mm Hg, bilaterally on thighs) or SHAM (20 mm Hg) at normobaric hypoxia (fraction of inspired oxygen [FiO2] of 16%). Performance and physiological (i.e., oxyhemoglobin saturation, heart rate, blood lactate, and vastus lateralis oxygenation) parameters were recorded. Time to complete (P = 0.011) 5-km TT and mean power output (P = 0.005) from TT1 to TT2 were worse in SHAM, but not in IPC (P = 0.381/P = 0.360, respectively). There were no differences in time, power output, or physiological variables during the two TT between IPC and SHAM. All muscle oxygenation indices differed (P < 0.001) during the IPC/SHAM with a greater deoxygenation in IPC. During the TT, there was a greater concentration of total hemoglobin in IPC than SHAM (P = 0.047) and greater total hemoglobin in TT1 than TT2. Further, the concentration of oxyhemoglobin was lower during TT2 than TT1 (P = 0.005). In moderate hypoxia, IPC allowed maintaining a higher blood volume during a subsequent maximal exercise, mitigating the performance decrement between two consecutive cycling TT.

Background: Aging decreases some capacities in older adults, sarcopenia being one of the common processes that occur and that interfered with strength capacity. The present study aimed to verify the acute effect of IPC on isometric handgrip strength and functional capacity in active elderly women. Methods: In a single-blind, placebo-controlled design, 16 active elderly women (68.1 ± 7.6 years) were randomly performed on three separate occasions a series of tests: (1) alone (control, CON); (2) after IPC (3 cycles of 5-min compression/5-min reperfusion at 15 mmHg above systolic blood pressure, IPC); and (3) after placebo compressions (SHAM). Testing included a handgrip isometric strength test (HIST) and three functional tests (FT): 30 s sit and stand up from a chair (30STS), get up and go time (TUG), and 6 min walk distance test (6MWT). Results: HIST significantly increased in IPC (29.3 ± 6.9 kgf) compared to CON (27.3 ± 7.1 kgf; 7.1% difference; p = 0.01), but not in SHAM (27.7 ± 7.9; 5.5%; p = 0.16). The 30STS increased in IPC (20.1 ± 4.1 repetitions) compared to SHAM (18.5 ± 3.5 repetitions; 8.7%; p = 0.01) and CON (18.5 ± 3.9 repetitions; 8.6%; p = 0.01). TUG was significantly lower in IPC (5.70 ± 1.35 s) compared to SHAM (6.14 ± 1.37 s; −7.2%; p = 0.01), but not CON (5.91 ± 1.45 s; −3.7%; p = 0.24). The 6MWT significantly increased in IPC (611.5 ± 93.8 m) compared to CON (546.1 ± 80.5 m; 12%; p = 0.02), but not in SHAM (598.7 ± 67.6 m; 2.1%; p = 0.85). Conclusions: These data suggest that IPC can promote acute improvements in handgrip strength and functional capacity in active elderly women.

This pilot study examined the effect of inspiratory muscle training (IMT) on repeated-sprint ability and vastus lateralis reoxygenation. Ten recreationally trained subjects were randomly divided into two groups to complete 4 weeks of IMT or Sham (placebo) training. Pre- and post-intervention, a repeated-sprint ability (RSA) test was performed in both normoxia and hypoxia (FiO2 ≈ 14.5%). Vastus lateralis reoxygenation (VLreoxy), defined as peak to minimum amplitude deoxyhaemoglobin for each sprint/recovery cycle, was assessed during all trials using near-infrared spectroscopy. For total work performed, power analysis revealed that for small, medium and large effects (Cohen’s f), sample sizes of n = 8, 16 and 90 respectively, are required to achieve a power of 80% at an α level of 0.05. Maximal inspiratory mouth pressure increased in IMT by 36.5%, 95% CI [20.9, 61.6] and by 2.7%, 95% CI [−4.46, 8.8] in Sham. No clear difference in the change of work completed during the sprints between groups were observed in normoxia (Sham −0.805 kJ, 95% CI [−3.92, 0.39]; IMT −2.06 kJ, 95% CI [−11.5, 4.96]; P = 0.802), or hypoxia (Sham −3.09 kJ, 95% CI [−7, 0.396]; IMT 0.354 kJ, 95% CI [−1.49, 2.1]; P = 0.802). VLreoxy in IMT increased by 9.34%, 95% CI [5.15, 13.7] in normoxia only. In conclusion, despite a large increase in IMT, this was only associated with a small effect on RSA in our pilot study cohort. Owing to a potentially relevant impact of training the inspiratory musculature, future studies should include a sample size of at least 16-20 to detect moderate to large effects on RSA.

Made available in DSpace on 2021-06-25T10:37:12Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-12-01 To investigate the effect of acute capsaicin (CAP) supplementation on time to exhaustion, physiological responses and energy systems contribution during continuous high-intensity exercise session in runners. Fifteen recreationally-Trained runners completed two randomized, double-blind continuous high-intensity exercises at the speed eliciting 90% VO 2peak(90% s VO 2peak), 45 minutes after consuming capsaicin or an isocaloric placebo. Time to exhaustion, blood lactate concentration, oxygen consumption during and 20-min post-exercise, energy systems contribution, time to reach VO 2peak, heart rate and the rate of perceived exertion (RPE) were evaluated. There was no significant difference between conditions for time to reach VO 2peak(CAP:391.71±221.8 vs. PLA:298.20±174.5 sec, ES:0.58, p=0.872), peak lactate (CAP:7.98±2.11 vs. PLA:8.58±2.15 μmol, ES:-0.28, p=0.257), time to exhaustion (CAP:654.28±195.44 vs. PLA:709.20±208.44 sec, ES:-0.28, p=0.462, end-of-exercise heart rate (CAP:177.6±14.9 vs. PLA:177.5±17.9 bpm, ES:-0.10, p=0.979) and end-of-exercise RPE (CAP: 19±0.8 vs. PLA: 18±2.4, ES: 0.89, p=0.623). In conclusion, acute CAP supplementation did not increase time to exhaustion during high-intensity continuous exercise nor alter physiological responses in runners Laboratory of Exercise Biochemistry Department of Physical Education Universidade Estadual de Londrina Département de Kinésiologie Université Laval Exercise and Immunometabolism Research Group Post-Graduation Prog. in Physiother.. Dept. of Phys. Educ.. State University of Sao Paulo (UNESP) School of T-echnology and Sciences. Presidente Prudente Physical Education University of Sao Paulo Department of Physical Education Unversidade Federal Do Piaui Exercise and Immunometabolism Research Group Post-Graduation Prog. in Moviment Sicences. Dept. of Phys. Educ.. State Univ. of Sao Paulo (UNESP School of Technology and Sciences. Presidente Prudente Exercise and Immunometabolism Research Group Post-Graduation Prog. in Physiother.. Dept. of Phys. Educ.. State University of Sao Paulo (UNESP) School of T-echnology and Sciences. Presidente Prudente Exercise and Immunometabolism Research Group Post-Graduation Prog. in Moviment Sicences. Dept. of Phys. Educ.. State Univ. of Sao Paulo (UNESP School of Technology and Sciences. Presidente Prudente

Individuals with low orthostatic tolerance show greater decrease in posterior cerebral artery mean blood velocity (PCAvmean). Since young fit women often experience presyncopal symptoms, their posterior cerebral circulation may be prone to greater decreases in PCAvmean, probably explained by an attenuated dynamic cerebral autoregulation (dCA). Regional differences in dCA have never been evaluated in young fit women. We compared dCA in the middle cerebral artery (MCA) and posterior cerebral artery (PCA) in 11 young fit women (25 ± 4y; ) in response to a sit-to-stand (5 min sitting followed by 5 min standing) and repeated squat-stand maneuvers performed at 0.05 Hz and 0.10 Hz. The cerebral pressure-flow relationship was characterized using four metrics: 1) percent reduction in blood velocity (BV) per percent reduction in MAP (% BV/% MAP) during initial orthostatic stress (0-15 s after sit-to-stand); 2) onset of the regulatory response (i.e. time delay before an increase in conductance (BV/MAP); 3) rate of regulation (RoR), following sit-to-stand and; 4) transfer function analysis (TFA) of forced MAP oscillations induced by repeated squat-stands. Upon standing, the relative decline in MCAvmean and PCAvmean was similar (−25 ± 9 vs. −30 ± 13%; p=0.29). The onset of the regulatory response (p=0.665), %ΔBV/%ΔMAP (p=0.129) and RoR (p=0.067) were not different between MCA and PCA. In regard to TFA, there was an ANOVA artery effect for gain (pNew findingsWhat is the central question of this study?Are there regional differences in the dynamic cerebral autoregulation in young fit women?What is the main finding and its importance?The key finding of this study is that there are no differences in dynamic cerebral autoregulation between both arteries. These results indicate that dynamic cerebral autoregulation does not seem to be responsible for making the posterior cerebral circulation more vulnerable to transient reduction in blood pressure in young fit women.

This study investigated the impact of repeated-sprint (RS) training with voluntary hypoventilation at low lung volume (VHL) on RS ability (RSA) and on performance in a 30-15 intermittent fitness test (30-15IFT). Over 4 weeks, 17 basketball players included eight sessions of straight-line running RS and RS with changes of direction into their usual training, performed either with normal breathing (CTL, n = 8) or with VHL (n = 9). Before and after the training, athletes completed a RSA test (12 × 30-m, 25-s rest) and a 30-15IFT. During the RSA test, the fastest sprint (RSAbest), time-based percentage decrement score (RSASdec), total electromyographic intensity (RMS), and spectrum frequency (MPF) of the biceps femoris and gastrocnemius muscles, and biceps femoris NIRS-derived oxygenation were assessed for every sprint. A capillary blood sample was also taken after the last sprint to analyse metabolic and ionic markers. Cohen's effect sizes (ES) were used to compare group differences. Compared with CTL, VHL did not clearly modify RSAbest, but likely lowered RSASdec (VHL: −24.5% vs. CTL: −5.9%, group difference: −19.8%, ES −0.44). VHL also lowered the maximal deoxygenation induced by sprints ([HHb]max; group difference: −2.9%, ES −0.72) and enhanced the reoxygenation during recovery periods ([HHb]min; group difference: −3.6%, ES −1.00). VHL increased RMS (group difference: 18.2%, ES 1.28) and maintained MPF toward higher frequencies (group difference: 9.8 ± 5.0%, ES 1.40). These changes were concomitant with a lower potassium (K+) concentration (group difference: −17.5%, ES −0.67), and the lowering in [K+] was largely correlated with RSASdec post-training in VHL only (r = 0.66, p < 0.05). However, VHL did not clearly alter PO2, hemoglobin, lactate and bicarbonate concentration and base excess. There was no difference between group velocity gains for the 30-15IFT (CTL: 6.9% vs. VHL: 7.5%, ES 0.07). These results indicate that RS training combined with VHL may improve RSA, which could be relevant to basketball player success. This gain may be attributed to greater muscle reoxygenation, enhanced muscle recruitment strategies, and improved K+ regulation to attenuate the development of muscle fatigue, especially in type-II muscle fibers.

Breath-hold divers are known to develop cardiac autonomic changes and brady-arrthymias during prolonged breath-holding (BH). The effects of BH-induced hypoxemia were investigated upon both cardiac ...

In healthy individuals at rest and while performing moderate-intensity exercise, systemic blood flow is distributed to tissues relative to their metabolic oxygen demands. During sustained high-intensity exercise, competition for oxygen delivery arises between locomotor and respiratory muscles, and the heightened metabolic work of breathing, therefore, contributes to limited skeletal muscle oxygenation and contractility. Intriguingly, this does not appear to be the case for intermittent-sprint work. This chapter presents new evidence, based on inspiratory muscle mechanical loading and hypoxic gas breathing, to support that the respiratory system of healthy men is capable of accommodating the oxygen needs of both locomotor and respiratory muscles when work is interspersed with short recovery periods. Only when moderate hypoxemia is induced, substantial oxygen competition arises in favour of the respiratory muscles. These findings extend our understanding of the relationship between mechanical and metabolic limits of varied exercise modes.

Purpose: To characterize the relationships between muscle oxygenation and performance during on- and off-water tests in highly trained sprint canoe–kayak athletes. Methods: A total of 30 athletes (19 kayakers and 11 canoeists) performed a maximal incremental test on a canoe or kayak ergometer for determination of VO2max and examination of the relation between peak power output (PPO) and physiological parameters. A subset of 21 athletes also performed a 200- and a 500- (for women) or 1000-m (for men) on-water time trial (TT). Near-infrared spectroscopy monitors were placed on the latissimus dorsi, biceps brachii, and vastus lateralis during all tests to assess changes in muscle O2 saturation (SmO2) and deoxyhemoglobin concentration ([HHb]). The minimum O2 oxygenation (SmO2min) and maximal O2 (Δ[HHb] extraction) were calculated for all subjects. Results: PPO was most strongly correlated with VO2max (R = .9), but there was also a large correlation between PPO and both SmO2min and Δ[HHb] in latissimus dorsi (R = −.5, R = .6) and vastus lateralis (R = −.6, R = .6, all P 2min in the 3 muscles combined (P P 2 extraction is a better predictor of performance than VO2max in sprint canoe–kayak. Conclusions: These results highlight the importance of peripheral adaptations in both short and long events and stress the relevance of adding muscle oxygenation measurements during testing and racing in sprint canoe–kayak.

It has been shown that an inspiratory muscle warm-up (IMW) could enhance performance. IMW may also improve the near-infrared spectroscopy (NIRS)-derived tissue oxygen saturation index (TSI) during cycling. However, there exists contradictory data about the effect of this conditioning strategy on performance and muscle oxygenation. We examined the effect of IMW on speed skating performance and studied the underpinning physiological mechanisms related to muscle oxygenation. In a crossover, randomized, single-blind study, eight elite speed skaters performed 3000 m on-ice time trials, preceded by either IMW (2 × 30 breaths, 40% maximal inspiratory pressure) or SHAM (2 × 30 breaths, 15% maximal inspiratory pressure). Changes in TSI, oxyhemoglobin–oxymyoglobin ([O2HbMb]), deoxyhemoglobin–deoxymyoglobin ([HHbMb]), total hemoglobin–myoglobin ([THbMb]) and HHbMbdiff ([O2HbMb]–[HHbMb]) in the right vastus lateralis muscle were monitored by NIRS. All variables were compared at different time points of the race simulation with repeated-measures analysis of variance. Differences between IMW and SHAM were also analyzed using Cohen’s effect size (ES) ± 90% confidence limits, and magnitude-based inferences. Compared with SHAM, IMW had no clear impact on skating time (IMW 262.88 ± 17.62 s vs. SHAM 264.05 ± 21.12 s, effect size (ES) 0.05; 90% confidence limits, − 0.22, 0.32, p = 0.7366), TSI, HbMbdiff, [THbMb], [O2HbMb] and perceptual responses. IMW did not modify skating time during a 3000 m time trial in speed skaters, in the conditions of our study. The unchanged [THbMb] and TSI demonstrate that the mechanisms by which IMW could possibly exert an effect on performance were unaffected by this intervention.

Near-infrared spectroscopy (NIRS) is a common tool used to study oxygen availability and utilization during repeated-sprint exercise. However, there are inconsistent methods of smoothing and determining peaks and nadirs from the NIRS signal, which make interpretation and comparisons between studies difficult. To examine the effects of averaging method on deoxyhaemoglobin concentration ([HHb]) trends, nine males performed ten 10-s sprints, with 30 seconds of recovery, and six analysis methods were used for determining peaks and nadirs in the [HHb] signal. First, means were calculated over predetermined windows in the last 5 and 2 seconds of each sprint and recovery period. Second, moving 5-seconds and 2-seconds averages were also applied, and peaks/nadirs were determined for each 40-seconds sprint/recovery cycle. Third, a Butterworth filter was used to smooth the signal, and the resulting signal output was used to determine peaks and nadirs from predetermined time points and a rolling approach. Correlation and residual analysis showed that the Butterworth filter attenuated the "noise" in the signal, while maintaining the integrity of the raw data (r = .9892; mean standardized residual -9.71 × 103 ± 3.80). Means derived from predetermined windows, irrespective of length and data smoothing, underestimated the magnitude of peak and nadir [HHb] compared to a rolling mean approach. Consequently, sprint-induced metabolic changes (inferred from Δ[HHb]) were underestimated. Based on these results, we suggest using a digital filter to smooth NIRS data, rather than an arithmetic mean, and a rolling approach to determine peaks and nadirs for accurate interpretation of muscle oxygenation trends.

The benefits of physical exercise on brain function and its metabolism are well documented, and it is established that acute aerobic exercise could enhance executive function. The aim of this study was to report the effect of exercise intensity during acute intermittent exercise (IE) on executive function and heart rate outcomes. Twenty male subjects performed a series of six consecutive 3-min bouts of exercise at either 60 or 95% of peak power output (PPO), interspersed by 3 min of passive recovery on a bicycle ergometer. Reaction time (ms) and accuracy (%) of switching task using a computerized Stroop task were recorded before and after warm-up, after each bout of exercise and every 15 min during a 1-h passive recovery following exercise. A two-way repeated measures ANOVA was performed to quantify the effects of exercise time (bouts) and condition (exercise intensity). The ANOVA revealed a main effect of time and an interaction between intensity and time for the heart rate and heart rate variability, RPE, and perceived difficulty of cognitive tasks (p