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The force drop after transcranial magnetic stimulation (TMS) delivered to the motor cortex during voluntary muscle contractions could inform about muscle relaxation properties. Because of the physiological relation between skeletal muscle fibertype distribution and size and muscle relaxation, TMS could be a noninvasive index of muscle relaxation in humans. By combining a noninvasive technique to record muscle relaxation in vivo (TMS) with the gold standard technique for muscle tissue sampling (muscle biopsy), we investigated the relation between TMS-induced muscle relaxation in unfatigued and fatigued states, and muscle fiber-type distribution and size. Sixteen participants (7F/9M) volunteered to participate. Maximal knee-extensor voluntary isometric contractions were performed with TMS before and after a 2-min sustained maximal voluntary isometric contraction. Vastus lateralis muscle tissue was obtained separately from the participants’ dominant limb. Fiber type I distribution and relative cross-sectional area of fiber type I correlated with TMS-induced muscle relaxation at baseline (r = 0.67, adjusted P = 0.01; r = 0.74, adjusted P = 0.004, respectively) and normalized TMS-induced muscle relaxation as a percentage of baseline (r = 0.50, adjusted P = 0.049; r = 0.56, adjusted P = 0.031, respectively). The variance in the normalized peak relaxation rate at baseline (59.8%, P < 0.001) and in the fatigue resistance (23.0%, P = 0.035) were explained by the relative cross-sectional area of fiber type I to total fiber area. Fiber type I proportional area influences TMS-induced muscle relaxation, suggesting TMS as an alternative method to noninvasively inform about skeletal muscle relaxation properties. NEW & NOTEWORTHY Transcranial magnetic stimulation (TMS)-induced muscle relaxation reflects intrinsic muscle contractile properties by interrupting the drive from the central nervous system during voluntary muscle contractions. We showed that fiber type I proportional area influences the TMS-induced muscle relaxation, suggesting that TMS could be used for the noninvasive estimation of muscle relaxation in unfatigued and fatigued human muscles when the feasibility of more direct method to study relaxation properties (i.e., muscle biopsy) is restricted. [ABSTRACT FROM AUTHOR]

Aim: Force expression is characterized by an interplay of biological and molecular determinants that are expected to differentiate males and females in terms of maximal performance. These include muscle characteristics (muscle size, fiber type, contractility), neuromuscular regulation (central and peripheral factors of force expression), and individual genetic factors (miRNAs and gene/protein expression). This research aims to comprehensively assess these physiological variables and their role as determinants of maximal force difference between sexes. Methods: Experimental evaluations include neuromuscular components of isometric contraction, intrinsic muscle characteristics (proteins and fiber type), and some biomarkers associated with muscle function (circulating miRNAs and gut microbiome) in 12 young and healthy males and 12 females. Results: Male strength superiority appears to stem primarily from muscle size while muscle fiber‐type distribution plays a crucial role in contractile properties. Moderate‐to‐strong pooled correlations between these muscle parameters were established with specific circulating miRNAs, as well as muscle and plasma proteins. Conclusion: Muscle size is crucial in explaining the differences in maximal voluntary isometric force generation between males and females with similar fiber type distribution. Potential physiological mechanisms are seen from associations between maximal force, skeletal muscle contractile properties, and biological markers. [ABSTRACT FROM AUTHOR]

The downward slope during the near‐infrared spectroscopy (NIRS)‐vascular occlusion test (NIRS‐VOT) is purported as a simplified estimate of metabolism. Whether or not the NIRS‐VOT exhibits sex‐ or limb‐specificity or may be acutely altered remains to be elucidated. Thus, we investigated if there is limb‐ or sex specificity in tissue desaturation rates (DeO2) during a NIRS‐VOT, and if acute dietary capsaicin may alter this estimate of muscle metabolism. Young healthy men (n = 25, 21 ± 4 years) and women (n = 20, 20 ± 1 years) ingested either placebo or capsaicin, in a counterbalanced, single‐blind, crossover design after which a simplified NIRS‐VOT was conducted to determine the DeO2 (%/s), as an estimate of oxidative muscle metabolism, in both the forearm (flexors) and thigh (vastus lateralis). There was a significant limb effect with the quadriceps having a greater DeO2 than the forearm (−2.31 ± 1.34 vs. −1.78 ± 1.22%/s, p = 0.007, ηp2 = 0.19). There was a significant effect of sex on DeO2 (p = 0.005, ηp2 = 0.203) with men exhibiting a lesser DeO2 than women (−1.73 ± 1.03 vs. −2.36 ± 1.32%/s, respectively). This manifested in significant interactions of limb*capsaicin (p = 0.001, ηp2 = 0.26) as well as limb*capsaicin*sex on DeO2 (p = 0.013, ηp2 = 0.16) being observed. Capsaicin does not clearly alter O2‐dependent muscle metabolism, but there was apparent limb and sex specificity, interacting with capsaicin in this NIRS‐derived assessment. [ABSTRACT FROM AUTHOR]

The clinical symptoms of chronic obstructive pulmonary disease (COPD) disease are accompanied by severely debilitating extra-pulmonary manifestations, including vascular dysfunction and hypertension. This systematic review evaluated the current evidence for several therapeutic interventions, targeting the nitric oxide (NO) pathway on hemodynamics and, secondarily, exercise capacity in patients with COPD. A comprehensive search on COPD and NO donors was performed on online databases. Of 934 initially found manuscripts, 27 were included in the review, and 16 in the meta-analysis. The analysis indicated inconsistent effects of dietary nitrate supplementation on exercise tolerance in COPD patients. Dietary nitrate supplementation decreased systolic (−3.7 ± 4.3 mmHg; p = 0.10) and diastolic blood pressure (BP; −2.6 ± 3.2 mmHg; p = 0.05) compared with placebo. When restricted to acute studies, a clinically relevant BP lowering effect of nitrate supplementation during diastole was observed (−4.7 ± 3.2 mmHg; n = 5; p = 0.05). In contrast, inhaled NO (iNO) at doses <20 ppm (+9.2 ± 11.3 mmHg) and 25–40 ppm (−5±2 mmHg) resulted in inconsistent effects on PaO 2 (p = 0.48). Data on the effect of iNO on exercise capacity were too limited and inconsistent, but preliminary evidence suggests a possible benefit of iNO on pulmonary vascular resistance during exercise in severe COPD patients. Overall, the effects of acute dietary nitrate supplementation on BP may be of clinical relevance as an adjunct therapy and deserve further investigation in large sample size studies of COPD patients with and without cardiovascular comorbidities. iNO exerted inconsistent physiological effects, with the use of high doses posing safety risks. • This systematic review evaluated therapeutics targeting the nitric oxide pathway in COPD. • Acute dietary nitrate supplementation lowered diastolic blood pressure in COPD patients. • The blood pressure lowering effect of dietary nitrate might be clinically important. • The impact of dietary nitrate on cardiovascular risks should be further explored. • The effects of inhaled nitric oxide is low or even detrimental in some conditions. [ABSTRACT FROM AUTHOR]

This study aims to test the separated and combined effects of mechanoreflex activation and nociception through exercise-induced muscle damage (EIMD) on central and peripheral hemodynamics before and during single passive leg movement (sPLM). Eight healthy young males undertook four experimental sessions, in which a sPLM was performed on the dominant limb while in each specific session the contralateral was: 1) in a resting condition (CTRL), 2) stretched (ST), 3) resting after EIMD called delayed onset muscle soreness (DOMS) condition, or 4) stretched after EIMD (DOMS + ST). EIMD was used to induce DOMS in the following 24–48 h. Femoral blood flow (FBF) was assessed using Doppler ultrasound whereas central hemodynamics were assessed via finger photoplethysmography. Leg vascular conductance (LVC) was calculated as FBF/mean arterial pressure (MAP). RR-intervals were analyzed in the time (root mean squared of successive intervals; RMSSD) and frequency domain [low frequency (LF)/high frequency (HF)]. Blood samples were collected before each condition and gene expression analysis showed increased fold changes for P2X4 and IL1β in DOMS and DOMS + ST compared with baseline. Resting FBF and LVC were decreased only in the DOMS + ST condition (−26 mL/min and −50 mL/mmHg/min respectively) with decreased RMSSD and increased LF/HF ratio. MAP, HR, CO, and SV were increased in ST and DOMS + ST compared with CTRL. Marked decreases of Δpeaks and AUC were observed for FBF (Δ: −146 mL/min and −265 mL respectively) and LVC (Δ: −8.66 mL/mmHg/min and ±1.7 mL/mmHg/min respectively) all P < 0.05. These results suggest that the combination of mechanoreflex and nociception resulted in decreased vagal tone and concomitant rise in sympathetic drive that led to increases in resting central hemodynamics with reduced limb blood flow before and during sPLM. NEW & NOTEWORTHY Exercise-induced muscle damage (EIMD) is a well-known model to study mechanical hyperalgesia and muscle peripheral nerve sensitizations. The combination of static stretching protocol on the damaged limb extensively increases resting central hemodynamics with reduction in resting limb blood flow and passive leg movement-induced hyperemia. The mechanism underlining these results may be linked to reduction of vagal tone with concomitant increase in sympathetic activity following mechano- and nociceptive activation. [ABSTRACT FROM AUTHOR]

Fatigue is one of the most disabling symptoms of multiple sclerosis (MS); it influences patients' quality of life. The etiology of fatigue is complex, and its pathogenesis is still unclear and debated. The objective of this review was to describe potential brain structural and functional dysfunctions underlying fatigue symptoms in patients with MS. To reach this purpose, a systematic review was conducted of published studies comparing functional brain activation and structural brain in MS patients with and without fatigue. Electronic databases were searched until 24 February 2021. The structural and functional outcomes were extracted from eligible studies and tabulated. Fifty studies were included: 32 reported structural brain differences between patients with and without fatigue; 14 studies described functional alterations in patients with fatigue compared to patients without it; and four studies showed structural and functional brain alterations in patients. The results revealed structural and functional abnormalities that could correlate to the symptom of fatigue in patients with MS. Several studies reported the differences between patients with fatigue and patients without fatigue in terms of conventional magnetic resonance imaging (MRI) outcomes and brain atrophy, specifically in the thalamus. Functional studies showed abnormal activation in the thalamus and in some regions of the sensorimotor network in patients with fatigue compared to patients without it. Patients with fatigue present more structural and functional alterations compared to patients without fatigue. Specifically, abnormal activation and atrophy of the thalamus and some regions of the sensorimotor network seem linked to fatigue. [ABSTRACT FROM AUTHOR]

Previous studies demonstrated that aging, neurodegeneration, and the level of physical activity are associated with vascular alterations. However, in Parkinson's disease (PD) only cerebral vascular function has been investigated; instead, the contribution of PD on systemic vascular function and skeletal muscle circulation remains a matter of debate. In this study, the hyperemic response during the single passive leg movement test (sPLM), largely nitric oxide dependent, was examined at the level of the common femoral artery with an ultrasound Doppler system to assess systemic vascular function in 10 subjects with PD (PDG), compared with 10 aged-sex and physically active matched healthy elderly (EHG), and 10 physically active young healthy individuals (YHG). Interestingly, femoral blood flow at rest, normalized for the thigh volume, was similar in PDG (64 ± 15 mL·min-1·L-1), EHG (44 ± 8 mL·min-1·L-1), and YHG (58 ± 11 mL·min-1·L-1, all P values > 0.05). The sPLM-induced hyperemic response appeared markedly lower in PDG and EHG compared with YHG (8.3 ± 0.1 vs. 9.8 ± 0.8 vs. 17.3 ± 3.0 mL·min-1·L-1; P < 0.05) but the difference between PDG and EHG was negligible (P > 0.05). The results of our study indicate that peripheral circulation and vascular function are not reduced in physically active patients with PD, suggesting that these vascular changes could resemble the physiological adjustments of aging, without any impact from the disease. [ABSTRACT FROM AUTHOR]

Muscle fatigue induced by voluntary exercise, which requires central motor drive, causes central fatigue that impairs endurance performance of a different, nonfatigued muscle. This study investigated the impact of quadriceps fatigue induced by electrically induced (no central motor drive) contractions on single-leg knee-extension (KE) performance of the subsequently exercising ipsilateral quadriceps. On two separate occasions, eight males completed constant-load (85% of maximal power-output) KE exercise to exhaustion. In a counterbalanced manner, subjects performed the KE exercise with no pre-existing quadriceps fatigue in the contralateral leg on one day (No-PreF), whereas on the other day, the same KE exercise was repeated following electrically induced quadriceps fatigue in the contralateral leg (PreF). Quadriceps fatigue was assessed by evaluating pre- to postexercise changes in potentiated twitch force (ΔQtw,pot; peripheral fatigue), and voluntary muscle activation (ΔVA; central fatigue). As reflected by the 57 ± 11% reduction in electrically evoked pulse force, the electrically induced fatigue protocol caused significant knee-extensors fatigue. KE endurance time to exhaustion was shorter during PreF compared with No-PreF (4.6 ± 1.2 vs 7.7 ± 2.4 min; P < 0.01). Although ΔQtw,pot was significantly larger in No-PreF compared with PreF (−60% vs −52%, P < 0.05), ΔVA was greater in PreF (−14% vs −10%, P < 0.05). Taken together, electrically induced quadriceps fatigue in the contralateral leg limits KE endurance performance and the development of peripheral fatigue in the ipsilateral leg. These findings support the hypothesis that the crossover effect of central fatigue is mainly mediated by group III/IV muscle afferent feedback and suggest that impairments associated with central motor drive may only play a minor role in this phenomenon. [ABSTRACT FROM AUTHOR]

Aim: Decreased muscle strength has been frequently observed in individuals with Parkinson's disease (PD). However, this condition is still poorly examined in physically active patients. This study compared quadriceps (Q) maximal force and the contribution of central and peripheral components of force production during a maximal isometric task between physically active PD and healthy individuals. In addition, the correlation between force determinants and energy expenditure indices were investigated. Methods: Maximal voluntary contraction (MVC), resting twitch (RT) force, pennation angle (θp), physiological cross‐sectional area (PCSA) and Q volume were assessed in 10 physically active PD and 10 healthy control (CTRL) individuals matched for age, sex and daily energy expenditure (DEE) profile. Results: No significant differences were observed between PD and CTRL in MVC (142 ± 85; 142 ± 47 N m), Q volume (1469 ± 379; 1466 ± 522 cm3), PCSA (206 ± 54; 205 ± 71 cm2), θp (14 ± 7; 13 ± 3 rad) and voluntary muscle‐specific torque (MVC/PCSA [67 ± 35; 66 ± 19 N m cm−2]). Daily calories and MVC correlated (r = 0.56, P =.0099). However, PD displayed lower maximal voluntary activation (MVA) (85 ± 7; 95 ± 5%), rate of torque development (RTD) in the 0‐0.05 (110 ± 70; 447 ± 461 N m s−1) and the 0.05‐0.1 s (156 ± 135; 437 ± 371 N m s−1) epochs of MVCs, whereas RT normalized for PCSA was higher (35 ± 14; 20 ± 6 N m cm−2). Conclusion: Physically active PDs show a preserved strength of the lower limb. This resulted by increasing skeletal muscle contractility, which counterbalances neuromuscular deterioration, likely due to their moderate level of physical activity. [ABSTRACT FROM AUTHOR]

Background: Exercise is highly recommended in patients with Parkinson's disease (PD). Exercise-induced amelioration of motor, non-motor, and drug-induced symptoms are widely known. However, specific guidelines on exercise testing and prescription in PD are lacking. Objective: This study reviews the literature on exercise-based approaches to the management of symptoms at each stage of the disease and evaluate: (1) the most suitable clinical exercise testing; (2) training programs based on testing outcomes and PD stage; (3) the effects of exercise on antiparkinsonian drugs and to suggest the most effective exercise–medication combination. Methods: A systematic search was conducted using the databases MEDLINE, Google Scholar and, Cochrane Library using "Parkinson's Disease AND Physical therapy", "Training AND Parkinson", "Exercise", "Exercise AND Drug" as key words. In addition, references list from the included articles were searched and cross-checked to identify any further potentially eligible studies. Results: Of a total of 115 records retrieved, 50 (43%) were included. From these, 23 were included under the rubric "exercise testing"; 20 focused on the effectiveness of different types of exercise in PD motor-functional symptoms and neuroprotective effects, throughout disease progression, were included under the rubric "training protocol prescription"; and 7 concern the rubric "interaction between exercise and medication", although none reported consistent results. Conclusions: Despite the lack of standardized parameters for exercise testing and prescription, all studies agree that PD patients should be encouraged to regularly train according to their severity-related limitations and their personalized treatment plan. In this manuscript, specific guidelines for tailored clinical testing and prescription are provided for each stage of PD. [ABSTRACT FROM AUTHOR]

Blood flow (BF) to exercising muscles is susceptible to variations of intensity, and duration of skeletal muscle contractions, cardiac cycle, blood velocity, and vessel dilation. During cyclic muscle activity, these elements may change proportionally with or without direct optimal temporal alignment, likely influencing BF to active muscle. Ideally, the pulsed delivery of blood to active muscle timed with the inactive phase of muscle duty-cycle would enhance the peak and average BF. To investigate the phenomenon of muscle contraction and pulse synchronicity, electrically evoked muscle contractions (trains of 20 Hz, 200-ms duration) were synchronized with each systolic phase of the anterograde blood velocity spectrum (aBVS). Specifically, unilateral quadriceps contractions matched in-phase (IP) with the aBVS were compared with contractions matched out-of-phase (OP) with the aBVS in 10 healthy participants (26 ± 3 yr). During each trial, femoral BF of the contracting limb and central hemodynamics were recorded for 5 min with an ultrasound Doppler, a plethysmograph, and a cardioimpedance device. At steady state (5th min) IP BF (454 ± 30 mL/min) and vascular conductance (4.3 ± 0.2 mL·min−1·mmHg−1), and OP MAP (108 ± 2 mmHg) were significantly lower (P < 0.001) in comparison to OP BF (784 ± 25 mL/min) and vascular conductance (6.7 ± 0.2 mL·min−1·mmHg−1), and IP MAP (113 ± 3 mmHg). On the contrary, no significant difference (all, P > 0.05) was observed between IP and OP central hemodynamics (HR: 79 ± 10 vs. 76 ± 11 bpm, CO: 8.0 ± 1.6 vs. 7.3 ± 1.6 L/min), and ventilatory patterns (V̇e:14 ± 2 vs. 14 ± 1 L/min, V̇o2:421 ± 70 vs. 397 ± 34 mL/min). The results suggest that muscle contractions occurring during OP that do not interfere with aBVS elicit a maximization of muscle functional hyperemia. NEW & NOTEWORTHY When muscle contraction is synchronized with the pulsed delivery of blood flow to active muscle, muscle functional hyperemia can be either maximized or minimized. This suggests a possibility to couple different strategies to enhance the acute and chronic effects of exercise on the cardiovascular system. [ABSTRACT FROM AUTHOR]

R5983 --> 885.8 --> Cardiovascular morbidity and mortality rates are highest among Black Americans (BA), the mechanisms of which are complex and not completely understood. Altered autonomic reflexes or sympathetic transduction could contribute to elevations in baseline blood pressure or an exaggerated exercise pressor response, thereby increasing CVD risk; though no studies have explored whether mechanoreflex sensitivity, a component of the exercise pressor reflex, is altered in BA. PURPOSE: Using passive leg movement (PLM), as model of activating the mechanoreflex and an assessment of lower limb vascular function, the aim of this study was to compare the central and peripheral hemodynamic responses in young healthy Black (BA) and White American (WA) males. METHODS: Young (21±4 yr) healthy BA (n = 9) and WA (n = 10) males, matched for physical activity, were instrumented to continuously monitor central and peripheral hemodynamics using Finger Photoplethysmography (Finometer) and frequency domain multi‐distance near‐infrared spectroscopy (NIRS) of the vastus lateralis (Oxiplex TS), respectively. After 1 minute of baseline, subjects underwent continuous PLM at 1 hz for two minutes, while tissue oxygen saturation (StO2%), cardiac output (CO), heart rate (HR), stroke volume (SV), and mean arterial pressure (MAP) were continuously recorded. RESULTS: Resting HR (61±3 vs. 62±3 beats/min), SV (89±5 vs. 92±5 mL/beat), CO (5.4±0.4 vs. 4.4±0.5 L/min), and MAP (92±5 vs. 86±3 mmHg) were not different between BA and WA, respectively (all, p>0.05). The individual peak PLM‐induced changes in HR (6±2 vs. 11±3 Δbeats/min, p = 0.06), SV (7.3±1.6 vs. 11.4±1.9 ΔmL/beat, p = 0.04), and CO (0.7±0.2 vs. 1.0±0.2 ΔL/min, p = 0.09) were lower in BA, however the MAP response (5.3±1.4 vs. 6.0±0.8 ΔmmHg, p > 0.05) was not different. The peak PLM‐induced change in StO2 was significantly attenuated in BA (1.6±0.5 vs. 3.8±0.4 Δ%, p=0.01). As a surrogate of nitric oxide, urinary nitrate+nitrate were not different between groups (2.89±1.67 vs. 2.00±1.35 μM, p>0.05). CONCLUSION: A novel insight from the current study reveals that Black American men had an attenuated mechanoreflex response to PLM as compared to White American men. However, Black Americans had a lower peripheral hemodynamic response, perhaps the result of the altered mechanoreflex or suggestive of lower limb vascular dysfunction, which might explain a propensity towards elevated rates of peripheral vascular disease in Black Americans. [ABSTRACT FROM AUTHOR]

Capsaicin (CAP) activates the transient receptor potential vanilloid 1 (TRPV1) channel on sensory neurons, improving ATP production, vascular function, fatigue resistance, and thus exercise performance. However, the underlying mechanisms of CAP-induced ergogenic effects and fatigue-resistance, remain elusive. To evaluate the potential anti-fatigue effects of CAP, 10 young healthy males performed constant-load cycling exercise time to exhaustion (TTE) trials (85% maximal work rate) after ingestion of placebo (PL; fiber) or CAP capsules in a blinded, counterbalanced, crossover design, while cardiorespiratory responses were monitored. Fatigue was assessed with the interpolated twitch technique, pre-post exercise, during isometric maximal voluntary contractions (MVC). No significant differences (p > 0.05) were detected in cardiorespiratory responses and self-reported fatigue (RPE scale) during the time trial or in TTE (375 ± 26 and 327 ± 36 s, respectively). CAP attenuated the reduction in potentiated twitch (PL: −52 ± 6 vs. CAP: −42 ± 11%, p = 0.037), and tended to attenuate the decline in maximal relaxation rate (PL: −47 ± 33 vs. CAP: −29 ± 68%, p = 0.057), but not maximal rate of force development, MVC, or voluntary muscle activation. Thus, CAP might attenuate neuromuscular fatigue through alterations in afferent signaling or neuromuscular relaxation kinetics, perhaps mediated via the sarco-endoplasmic reticulum Ca2+ ATPase (SERCA) pumps, thereby increasing the rate of Ca2+ reuptake and relaxation. [ABSTRACT FROM AUTHOR]

L5118 --> Previous work in vitro suggests that capsaicin, the spicy ingredient in peppers, attenuates the vascular response to sympathetic activity ("sympatholysis"), likely mediated through vascular transient receptor potential vanilloid type 1 (TRPV1), and was associated with improved vascular function, though translational studies are needed. Further, given racial disparities in vascular function, and reported racial differences in sensory TRPV1 activity, exploring the potential TRPV1‐related mechanisms underpinning these vascular differences is warranted. Purpose: To determine if racial differences existed in the central hemodynamic responses to sympathetic stimuli, via lower body negative pressure (LBNP) at rest and during exercise. Second, using an acute dose of oral capsaicin, we sought to determine the potential role of TRPV1 receptors in mediating any racial differences in sympatholysis or vascular function. Methods: In a blinded placebo‐controlled crossover design, 23 young healthy black (BM, n=13, 23±5 yrs) and white males (WM, n=10, 19±1 yrs) were given capsules containing either placebo (800mg fiber) or capsaicin (780 mg Chile pepper extract, 2.4±0.04 mg capsaicin, 0.5±0.04 mg dihydrocapsaicin). To assess microvascular responses, frequency‐domain, multi‐distance, near infrared spectroscopy (NIRS) was placed over the muscular medial forearm (i.e. flexor digitorum profundus) providing measure of oxyhemoglobin (HbO, in μM). Central hemodynamics, namely stroke volume (SV), cardiac output (CO), mean arterial pressure (MAP), and heart rate (HR), were measured continuously using a Finometer. To assess hemodynamic responses and potential differences in sympatholysis, these measures performed at rest, during LBNP (‐20 mmHg), handgrip (HG) exercise (30% MVC), and HG+LBNP. Results: Under placebo conditions, at rest HR, SV, CO, and MAP were not different between BM and WM (p>0.05), and groups were unaffected by capsaicin (p>0.05). The LBNP‐induced changes at rest appeared larger for black males (SV ‐18±4ml vs. ‐8±11ml and MAP 4.6±6 vs. 1.3± 5mmHg, BM vs. WM), which were seemingly reversed with acute capsaicin (SV ‐11±13 vs. ‐9±16ml and MAP ‐2±9 vs. 1.2± 8mmHg, BM vs. WM). At rest, with placebo, the LBNP‐induced ΔHbO, was similar between groups (‐2±6 vs. ‐2±2μM, BM vs WM), and relatively unaffected by capsaicin (‐3±6 vs. ‐1±2 μM, BM vs WM). During HG exercise, the LBNP‐induced ΔHbO was disparate between groups (‐5±7 vs. 1±3 μM, BM vs WM), and this difference was ablated by the capsaicin (1±6 vs. 2±2 μM, BM vs WM). Conclusion: There were racial differences in the central and peripheral hemodynamic response to LBNP at rest and during exercise, suggesting impaired sympatholysis or altered autonomic regulation. Capsaicin, and assumed activation of TRPV1 receptors, seems to affect the hemodynamic response to LBNP, in a relatively race‐specific manner at rest and during exercise, potentially mitigating race‐related differences. Further work is needed to determine whether such differences may be due to altered TRPV1 expression between groups. [ABSTRACT FROM AUTHOR]

R2867 --> The pungent bioactive ingredient in peppers (Capsaicin; CAP) has been widely investigated for its activation of the transient receptor potential vanilloid 1 (TRPV1) channel on sensory neurons. It has been shown to improve mitochondrial biogenesis, adenosine triphosphate (ATP) production and vascular function. In animal models has been demonstrated that increases exercise performance and decreases fatigue development. However, whether acute oral CAP improves endurance performance and the potential underlying mechanisms remains elusive. This study aimed to evaluate the potential ergogenic and anti‐fatigue effects of acute oral CAP supplementation in healthy humans. In a double‐blind, placebo‐controlled, cross‐over design, 10 young healthy males performed constant‐load cycling exercise (294±55W; 85% of peak power output) to exhaustion, after acute ingestion of placebo (PL; 1000mg fiber pill) and CAP (780mg pill) capsules. Fatigue was assessed on the dominant quadriceps with the interpolated twitch technique, via changes in supramaximal electrical stimulation pre‐ vs. post‐exercise, during isometric maximal voluntary contractions (MVC) and at rest. Cardiopulmonary parameters (heart rate, cardiac output, oxygen consumption, ventilation) were assessed throughout the exercise. No statistically significant differences were detected in the muscle contractile functions, despite a trend (P=0.07) for a decreased time to exhaustion during CAP (PL: 369±85 vs. CAP: 296±64 sec). All the values (except muscle voluntary activation (%VMA)) significantly decreased from pre‐ to post‐exercise in both conditions. The exercise‐induced attenuation of the intrinsic muscle contractile properties (Maximal rate of force development (MRFD) and Maximal relaxation rate (MRR) of the resting twitch force) were mitigated, in part, by CAP. Notably, in the PL condition MRR was seemingly reduced by 47±33%, while only of 29±68% in CAP; contrarily, MRFD decreased similarly of 47±23% and of 40±27% in PL and CAP, respectively. In 9 participants, the resting twitch (estimate of peripheral muscle fatigue) pre‐ vs. post‐exercise decreased less with CAP (PL: 44±17 vs. CAP: 37±13%). CAP did not influence the MVC nor %VMA. The cardiopulmonary responses were similar between the conditions (P>0.05). In contrast to prior work, acute oral capsaicin did not improve endurance performance in the present study. CAP did elicit a tendency for faster relaxation rate, which might suggest an enhanced activation of the sarcoendoplasmic reticulum calcium ATPase (SERCA) pumps, thereby increasing the rate of Ca2+ reuptake and relaxation. However, this altered Ca2+ handling might also increase ATP demand. The tendency for CAP to attenuate the exercise‐induced reduction in muscle function, or fatigue, might provide a mechanistic basis for the previously demonstrated beneficial effects of CAP. Further work is needed in larger samples, to further determine the optimal dosing and loading strategies, to better understand the potential ergogenic effects of capsaicin. [ABSTRACT FROM AUTHOR]

Sarcopenia refers to a condition of progressive loss of skeletal muscle mass and function associated with a higher risk of falls and fractures in older adults. Musculoskeletal aging leads to reduced muscle mass and strength, affecting the quality of life in elderly people. In recent years, several studies contributed to improve the knowledge of the pathophysiological alterations that lead to skeletal muscle dysfunction; however, the molecular mechanisms underlying sarcopenia are still not fully understood. Muscle development and homeostasis require a fine gene expression modulation by mechanisms in which microRNAs (miRNAs) play a crucial role. miRNAs modulate key steps of skeletal myogenesis including satellite cells renewal, skeletal muscle plasticity, and regeneration. Here, we provide an overview of the general aspects of muscle regeneration and miRNAs role in skeletal mass homeostasis and plasticity with a special interest in their expression in sarcopenia and skeletal muscle adaptation to exercise in the elderly. [ABSTRACT FROM AUTHOR]

Background: Load carriage (LC), which directly affects the chest wall and locomotor muscles, has been suggested to alter the ventilatory and circulatory responses to exercise, leading to increased respiratory muscle work and fatigue. However, studies exploring the impact of LC on locomotion increased internal work, complicating their interpretation. To overcome this issue, we sought to determine the effect of chest wall loading with restriction (CWL + R) on cycling performance, cardiopulmonary responses, microvascular responsiveness, and perceptions of fatigue. Methods: In a randomized crossover design, 23 young healthy males (22 ± 4 years) completed a 5 km cycling time trial (TT) in loaded (CWL + R; tightened vest with 10% body weight) and unloaded conditions. After baseline pulmonary function testing (PFT; forced expiratory volume in 1 s, FEV1; forced vital capacity, FVC), cardiopulmonary indices (HR, heart rate; O2 uptake, VO2; ventilation, VE; tidal volume, VT; and breathing frequency, Bf), rating of perceived exertion (RPE), lactate (BLa), and microvascular responses (oxy-, deoxy-, total hemoglobin; and tissue saturation; StO2) of the vastus lateralis using near infrared spectroscopy were collected during the TT; and PFT was repeated post-exercise. Results: Pre-exercise, CWL + R reduced (p < 0.05) FVC (5.6 ± 0.8 versus 5.5 ± 0.7 L), FEV1 (4.8 ± 0.7 versus 4.7 ± 0.6 L), and FEV1/FVC (0.9 ± 0.1 versus 0.8 ± 0.1). CWL + R modified power output (PO) over time (interaction, p = 0.02), although the 5 km time (461 ± 24 versus 470 ± 27 s), VT (3.0 ± 0.3 versus 2.8 ± 0.8 L), Bf, VE, HR, VO2, microvascular and perceptual (visual analog scale, or VAS, and RPE) responses were unchanged (p > 0.05). CWL + R increased (p < 0.05) the average BLa (7.6 ± 2.6 versus 8.6 ± 3 mmol/L). Conclusions: Modest CWL + R negatively affects pre-exercise pulmonary function, modifies cycling power output over time, and increases lactate production during a 5 km cycling trial, although the cardiorespiratory, microvascular, and perceptual responses were unaffected. [ABSTRACT FROM AUTHOR]

• Transcranial magnetic stimulation (TMS)-induced muscle relaxation demonstrates high within- and between-session reliability in unfatigued and fatigued knee-extensor muscles. • TMS is a useful technique that researchers can use when investigating changes in muscle relaxation rates both in unfatigued and fatigued knee-extensor muscles. • In both healthy individuals and patient groups, TMS-induced muscle relaxation could be used for therapy effect monitoring and diagnostic purposes. Transcranial magnetic stimulation (TMS)-induced relaxation rate reflects intrinsic muscle contractile properties by interrupting the drive from the central nervous system during voluntary muscle contractions. To determine the appropriateness of knee-extensor muscle relaxation measurements induced by TMS, this study aimed to establish both the within- and between-session reliability before and after a fatiguing exercise bout. Eighteen participants (9 females, 9 males, age 25 ± 2 years, height 171 ± 9 cm, body mass 68.5 ± 13.5 kg) volunteered to participate in two identical sessions approximately 30 days apart. Maximal and submaximal neuromuscular evaluations were performed with TMS six times before (PRE) and at the end (POST) of a 2-min sustained maximal voluntary isometric contraction. Within- and between-session reliability of PRE values were assessed with intraclass correlation coefficient (ICC 2,1 , relative reliability), repeatability coefficient (absolute reliability), and coefficient of variation (variability). Test-retest reliability of post-exercise muscle relaxation rates was assessed with Bland-Altman plots. For both the absolute and normalized peak relaxation rates and time to peak relaxation, data demonstrated low variability (e.g. coefficient of variation ≤ 7.8%) and high reliability (e.g. ICC 2,1 ≥ 0.963). Bland-Altman plots showed low systematic errors. These findings establish the reliability of TMS-induced muscle relaxation rates in unfatigued and fatigued knee-extensor muscles, showing that TMS is a useful technique that researchers can use when investigating changes in muscle relaxation rates both in unfatigued and fatigued knee-extensor muscles. [ABSTRACT FROM AUTHOR]