Effects of Beetroot-Based Supplements on Muscular Endurance and Strength in Healthy Male Individuals: A Systematic Review and Meta-Analysis.

The aim of this study was to systematically review the current literature and analyze the effects of beetroot-based supplements (BRS) on muscular performance. Randomized controlled trials that assessed the acute or short-term effects of BRS administration on muscular endurance and/or strength in healthy male individuals were retrieved from PubMed, EMBASE, CENTRAL, and Web of Science databases from inception to February 20th, 2023. In addition, we also searched preprint papers in medRxiv.org, bibRxiv.org; thesis and dissertations included in oatd.org; and clinical trials published in ClinicalTrials.gov. Data extraction, risk of bias, and study quality were assessed by 2 authors. Meta-analyses and subgroup analyses of standardized mean differences (SMD) were performed using a random-effects model. A total of 1486 records were identified in the databases and 2 were obtained by manual search in the reference list. Of those, 27 studies attended eligibility criteria and composed this systematic review. BRS administration resulted in a positive effect on muscular endurance (SMD: 0.31; 95% confidence interval (CI): 0.10 to 0.51; p < 0.01; n = 16 studies). There was an overall significative effect for muscular strength (SMD: 0.26; 95% CI: 0.03 to 0.48; p < 0.05; n = 18 studies), but a subgroup analysis showed that significant effects were found when strength was measured in a fatigued (SMD: 0.64; 95% CI: 0.25 to 1.03; p < 0.01), but not resting state. BRS administration have a small ergogenic effect on muscular endurance and attenuate the decline in muscular strength in a fatigued state in healthy male individuals.

Beetroot-based supplements can improve muscular endurance and attenuates the decline in muscular strength. These effects are attributed to the inorganic nitrate contained in these products, which ranged from 316­985 mg/day, ingested 2­3 hours before exercise.Beetroot-based supplements administration can generate a modest increase in the number of repetitions performed to failure or in exercise time to exhaustion, which may contribute to the performance and optimization of the results of people involved in isotonic exercises (e.g., resistance training).Beetroot-based supplements ingestion can improve muscular strength, particularly it aids in the recovery of muscular strength after a fatiguing task.

Role of the Inspiratory Muscles on Functional Performance From Critical Care to Hospital Discharge and Beyond in Patients With COVID-19.

OBJECTIVE: The role of inspiratory muscle performance in functional performance in patients with coronavirus disease 2019 (COVID-19) is poorly understood. The purpose of this study was to perform a longitudinal examination of inspiratory and functional performance from intensive care unit (ICU) discharge (ICUD) to hospital discharge (HD) and symptoms at HD and 1 month after HD in patients with COVID-19. METHODS: Thirty patients (19 men, 11 women) with COVID-19 were included. Examination of inspiratory muscle performance at ICUD and HD was performed with an electronic manometer, which provided the maximal inspiratory pressure (MIP) and several other inspiratory measures. Examination of dyspnea and functional performance was performed at ICUD and HD with the Modified Borg Dyspnea Scale and the 1-minute sit-to-stand test (1MSST), respectively. RESULTS: The mean age was 71 (SD = 11) years, the mean length of ICU stay was 9 (SD = 6) days, and the mean length of hospital stay was 26 (SD = 16) days. Most of the patients were diagnosed with severe COVID-19 (76.7%) and had a mean Charlson Comorbidity Index of 4.4 (SD = 1.9), reflecting high comorbidity. The mean MIP of the entire cohort increased minimally from ICUD to HD (from 36 [SD = 21] to 40 [SD = 20] cm H2O), reflecting predicted values for men and women at ICUD and HD of 46 (25%) to 51 (23%) and 37 (24%) to 37 (20%), respectively. The 1MSTS score increased significantly from ICUD to HD (9.9 [SD = 7.1] vs 17.7 [SD = 11.1]) for the entire cohort but remained far below population-based reference values (2.5th percentile) for the majority of patients at ICUD and HD. At ICUD, MIP was found to be a significant predictor of a favorable change in 1MSTS performance (ß = 0.308; odds ratio = 1.36) at HD. CONCLUSION: A significant reduction in inspiratory and functional performance exists in patients with COVID-19 at both ICUD and HD, with a greater MIP at ICUD being a significant predictor of a greater 1MSTS score at HD. IMPACT: This study shows that inspiratory muscle training may be an important adjunct after COVID-19.

Differences Between Pullover and Pulldown Exercises on Maximal Isometric Force and Myoelectric Activity in Recreationally-Trained Men.

The aim of the present study was to compare the myoelectric activation and peak force (PF) between pullover (PO) and pulldown (PW) exercises in different shoulder joint positions during maximal isometric contractions (0o, 45o, 90o, 135o, and 180°). Fifteen young, healthy, resistance-trained men were recruited. The participants performed three maximal voluntary isometric contractions for each exercise at five shoulder joint positions. The myoelectric activation (iEMG) from pectoralis major (PM); latissimus dorsi (LD); posterior deltoid (PD), and PF were measured. For PF, there were significant main effects for exercise and joint positions (p < 0.001). For iEMG PM, there was significant a main effect for joint positions (p < 0.001). There was a significant interaction between exercises and joint positions (p < 0.001). For iEMG LD, there was a significant main effect for joint positions (p < 0.001). There was no significant interaction between exercises and joint positions. For iEMG PD, there was a significant main effect for joint positions (p < 0.001). There was no significant interaction between exercises and joint positions. For RPE, there were no significant differences between exercises and joint positions. The study concludes that specific shoulder joint positions affect PF production and iEMG during both exercises. RPE was not affected.

The functional and molecular effects of problematic alcohol consumption on skeletal muscle: a focus on athletic performance.

Background: Chronic alcohol misuse is associated with alcoholic myopathy, characterized by skeletal muscle weakness and atrophy. Moreover, there is evidence that sports-related people seem to exhibit a greater prevalence of problematic alcohol consumption, especially binge drinking (BD), which might not cause alcoholic myopathy but can negatively impact muscle function and amateur and professional athletic performance.Objective: To review the literature concerning the effects of alcohol consumption on skeletal muscle function and structure that can affect muscle performance.Methodology: We examined the currently available literature (PubMed, Google Scholars) to develop a narrative review summarizing the knowledge about the effects of alcohol on skeletal muscle function and exercise performance, obtained from studies in human beings and animal models for problematic alcohol consumption.Results: Exercise- and sport-based studies indicate that alcohol consumption can negatively affect muscle recovery after vigorous exercise, especially in men, while women seem less affected. Clinical studies and pre-clinical laboratory research have led to the knowledge of some of the mechanisms involved in alcohol-related muscle dysfunction, including an imbalance between anabolic and catabolic pathways, reduced regeneration, increased inflammation and fibrosis, and deficiencies in energetic balance and mitochondrial function. These pathological features can appear not only under chronic alcohol misuse but also in other alcohol consumption patterns.Conclusions: Most laboratory-based studies use chronic or acute alcohol exposure, while episodic BD, the most common drinking pattern in amateur and professional athletes, is underrepresented. Nevertheless, alcohol consumption negatively affects skeletal muscle health through different mechanisms, which collectively might contribute to reduced sports performance.

Comparison between cryotherapy and photobiomodulation in muscle recovery: a systematic review and meta-analysis.

The purpose of this study is to compare the effect of photobiomodulation therapy (PBMT) and cryotherapy (CRT) on muscle recovery outcomes. These searches were performed in PubMed, PEDro, CENTRAL, and VHL (which includes the Lilacs, Medline, and SciELO database) from inception to June 2021. We included randomized clinical trials involved healthy human volunteers (> 18 years) underwent an intervention of PBMT and CRT, when used in both isolated form post-exercise. Standardized mean differences (SMD) or mean difference (MD) with 95% confidence interval were calculated and pooled in a meta-analysis for synthesis. The risk of bias and quality of evidence were assessed through Cochrane risk-of-bias tool and GRADE system. Four articles (66 participants) with a high to low risk of bias were included. The certainty of evidence was classified as moderate to very low. PBMT was estimated to improve the muscle strength (SMD = 1.73, CI 95% 1.33 to 2.13, I2 = 27%, p < 0.00001), reduce delayed onset muscle soreness (MD: - 25.69%, CI 95% - 34.42 to - 16.97, I2 = 89%, p < 0.00001), and lower the concentration of biomarkers of muscle damage (SMD = - 1.48, CI 95% - 1.93 to - 1.03, I2 = 76%, p < 0,00,001) when compared with CRT. There was no difference in oxidative stress and inflammatory levels. Based on our findings, the use of PBMT in muscle recovery after high-intensity exercise appears to be beneficial, provides a clinically important effect, and seems to be the best option when compared to CRT.

Alternating Current Is More Fatigable Than Pulsed Current in People Who Are Healthy: A Double-Blind, Randomized Crossover Trial.

OBJECTIVE: Tolerance level and rapid fatigue onset are limitations in the use of neuromuscular electrical stimulation (NMES) as an electrotherapeutic resource in rehabilitation and training protocols; however, it is unclear if pulsed current (PC) and alternating current (AC) produce different fatigue levels when applied at submaximal contraction level. The purpose of this study was to compare fatigue and discomfort levels between PC and AC during a submaximal contraction protocol in people who are healthy. METHODS: In this double-blind, randomized crossover trial conducted in a laboratory setting, 30 male volunteers [23.23 years of age (SD = 4.59)] performed 2 submaximal fatigue protocols (with a 7-day interval) in a randomized order: PC (pulse duration = 2 milliseconds, pulse frequency = 100 Hz) and AC (2.5 kHz, pulse duration = 0.4 milliseconds, burst frequency = 100 Hz). NMES currents were applied to the knee extensor motor point of the dominant limb. The NMES protocol consisted of 80 evoked contractions (time on:off = 5:10 seconds) and lasted 20 minutes. The current was maintained at a constant intensity throughout the NMES protocol. The primary outcome measures were maximal voluntary isometric contraction, fatigue index (evoked torque decline), fatigability (number of contractions for a 50% drop in evoked-torque from the protocol start), total evoked torque-time integral (TTI), decline in TTI, and discomfort level. RESULTS: AC at 2.5 kHz demonstrated higher maximal voluntary isometric contraction decline post-fatigue, higher fatigue index, higher fatigability (ie, fewer contractions to reach the 50% evoked torque decline from the protocol start), smaller total TTI, and higher TTI decline compared with PC. No between-currents difference was observed in discomfort level. CONCLUSION: PC is less fatigable than AC at 2.5 kHz. IMPACT: Based on this study, PC is the preferred current choice when the NMES goal is to generate higher muscle work, higher mechanical load, and smaller fatigability during training both for athletes who are healthy and for rehabilitation programs for people with disease or injury.

Muscle excitation, force response, and efficiency during explosive force production after diacutaneous fibrolysis on lateral gastrocnemius of recreational athletes.

OBJECTIVE: Fibrous adhesions impair normal muscle mechanics. The present study aimed to assess lateral gastrocnemius muscle excitation, isometric force response, and neuromuscular efficiency during explosive force in plantarflexion before and after diacutaneous fibrolysis. METHODS: Thirty-five recreational athletes were allocated in the intervention group (n = 20) treated with diacutaneous fibrolysis, while the sham group (n = 15) was treated with placebo diacutaneous fibrolysis. Force response synchronized with surface electromyography during a plantarflexion task was collected. RESULTS: Differences between Pre- and Post-diacutaneous fibrolysis were observed for all variables, except for the placebo group. CONCLUSIONS: Diacutaneous fibrolysis was effective to increase force, muscle excitation, and neuromuscular efficiency on lateral gastrocnemius.

Effect of 12 Weeks of Endurance Training Combined with Creatine Supplement, Photobiomodulation Therapy, or Both on Performance and Muscle Damage in Rats.

Background: Photobiomodulation therapy (PBMT) and creatine (Cr) intake have been used in conjunction with heavy training, but little is known about their possible effects during a long-term training program. Objective: We assessed long-term use of PBMT and Cr in an exercise training program. Methods: Twenty-five male Wistar rats weighing ∼300 g were randomly allocated to one of five groups: a nontraining control group, a training group, a training group receiving Cr, a training group receiving PBMT, and a training group receiving both PBMT and Cr. The training program consisted of 12 weeks of daily swimming training. PBMT was delivered in six points with a laser device (808 nm, 100 mW, 30 sec per point of irradiation, 3 J, 75 J/cm2). Results: All training groups showed significantly higher peak force and longer time to 50% decay of force, and lower creatine kinase (CK) levels than the nontraining control group, thus confirming the benefit of the training program. In all outcomes related to muscle performance, the groups receiving PBMT with or without Cr supplement performed significantly better (p < 0.05) peak force and time of force decay during an electrical stimulation protocol than all the other groups. In addition, CK levels were also significantly lower for the PBMT groups than for the other groups. Conclusions: We conclude that PBMT alone or in conjunction with Cr supplement during a 12-week training program resulted in significantly better muscle performance and lower levels of CK, a biochemical marker of muscle damage.

Efeito agudo de diferentes períodos de foam rolling sobre o salto vertical contramovimento / Influence of the physical activity level on the quality of life and humor states of university professors

Vários métodos de aquecimento têm sido empregados no campo do treinamento esportivo . O foam rolling (FR) é uma das técnicas mais populares. No entanto, permanece o esclarecimento so bre o s períodos ótimos de FR para melhorar ou manter o desempenho. Portanto, o objetivo do presente estudo foi explorar o efeito agudo de diferentes períodos do FR no desempenho do salto vertical contramov iment o (SV). Doze indivíduos recreacionalmente ativos (23,92 ± 4,08 anos, 7 0 ± 1 2 k g, 1 71 ± 8 cm ) fo ram voluntários para o estudo. Todos os participantes completaram todos os protocolos ex perim en tais co m entrada randomizada. Os participantes realizaram seis visitas separadas por 48 horas. A primeira sessão incluiu a coleta de dados antropométricos, familiarização com o FR e a técnica do SV. Em seguida, cin co protocolos experimentais foram executados em ordem aleatória: Protocolo controle (PC) - salto v ertical sem FR; P30 ­ uma série de 30 segundos de FR antes do salto vertical; P60 - duas séries de 30 segun do s de FR; P90: três séries de 30 segundos de FR; P120 ­ quatro séries de 30 segundos de FR. O FR foi implementado para quadríceps, isquiotibiais, glúteo e gastrocnêmio. Diferenças significativas no desempenho do salto vertical (p <0,012) foram observadas no P30 (47,4 ± 11,7 cm), P60 (48,9 ± 11,9 cm), P90 (48,5 ± 12,1cm), P120 (48,6 ± 11,3 cm) em relação à PC (46,8 ± 11,3 cm). Além disso , P 60, P9 0, P120 apresentaram maior desempenho de salto vertical em relação ao p rotocolo P3 0. Po rtanto , o s praticantes e treinadores devem considerar a utilização de 60-120 segundos de FR durante o aquecimento, com o objetivo de melhorar o desempenho do SV...(AU)

Several warm-up methods have been employed in the field of athletic training. Th e foam rolling (FR) is one of the most popular techniques; however, there is still a lack o f ev idence abo ut t he optimal FR periods to enhance strength performance. Therefore, the purpose of the present study was t o explore the acute effect of different periods of the FR on vertical countermovement jump. Twelve recreationally active individuals (23.92 ± 4.08 years, 70 ± 12 kg, 171 ± 8cm) volunteered for t he st udy . Treatment conditions were participants using a random assignment. Participan ts p erform ed six v isit s separated by 48 hours. The first session included the collection of anthropometric data and familiarizatio n with a foam roller and the vertical countermovement jump technique. Then, five experimental p rotocols were employed in a randomized order: control protocol (CP) - the vertical countermovement without FR; P30 - one set of 30 seconds of FR before the vertical jump; P60 - two sets of 30 seconds of FR; P90: three sets of 30 seconds of FR; P120 - four sets of 30 seconds of FR. The FR was implemented for quadriceps, hamstrings, gluteus, and gastrocnemius. Significant differences in vertical countermovement jump performance (p < 0.012) were observed under the P30 (47.4 ± 11.7 cm), P60 (48.9 ± 11.9 cm), P90 (48.5 ± 12.1), P120 (48.6 ± 11.3 cm) compared to CP (46.8 ± 11.3 cm). In addit io n, P60 , P 90 , P 12 0 sh o wed greater vertical jump performance compared to the P30 protocol. Therefore, t he p ractition ers sh o uld consider utilizing 60-120 seconds of FR during the warm-up with the goal of acutely improving the vertical countermovement jump performance...(AU)

Effects of beta-alanine supplementation on muscle function during recovery from resistance exercise in young adults.

ß-Alanine supplementation has been shown to increase muscle carnosine levels and exercise performance. However, its effects on muscle recovery from resistance exercise (RE) remains unknown. The purpose of this study was to investigate the effects of ß-alanine supplementation on muscle function during recovery from a single session of high-intensity RE. Twenty-four untrained young adults (22.1 ± 4.6 years old) were assigned to one of two groups (N = 12 per group): a placebo-supplement group (4.8 g/day) or an ß-alanine-supplement group (4.8 g/day). The groups completed a single session of high-intensity RE after 28 days of supplementation and were then evaluated for muscle function on the three subsequent days (at 24, 48, and 72 h postexercise) to assess the time course of muscle recovery. The following indicators of muscle recovery were assessed: number of repetitions until failure, rating of perceived exertion, muscle soreness, and blood levels of creatine kinase (CK). Number of repetitions until failure increased from 24 to 48 h and 72 h of recovery (time P < 0.01), with no difference between groups. There was a significant increase in the rating of perceived exertion among the sets during the RE session (time P < 0.01), with no difference between the groups. No difference was observed over time and between groups in rating of perceived exertion in the functional tests during recovery period. Blood CK levels and muscle soreness increased at 24 h postexercise and then progressively declined at 48 and 72 h postexercise, respectively (time P < 0.05), with no difference between groups. In conclusion, our data indicate that ß-alanine supplementation does not improve muscle recovery following a high-intensity RE session in untrained young adults.

Investigating the clinical effect of kinesio tape on muscle performance in healthy young soccer players - a prospective cohort study

OBJECTIVE: Kinesio tape (KT) is a visible adhesive restorative tape that has typically been utilized for injury prevention, recovery, and even performance improvement, but limited studies have assessed the effect of KT on muscle performance. The purpose of this study was to investigate the clinical impact of KT on muscle performance in healthy young soccer players. METHODS: Between 25 March and 21 April 2017, sixteen healthy soccer players with a mean age of 20±2.17 were enrolled in this prospective cohort study. All participants were selected from the college football team of Prince Sattam Bin Abdulaziz University. The muscle performance of the players was evaluated with an isokinetic dynamometer for the following three conditions: without tape, immediately after applying KT, and 8 hrs post-KT application while the tape remained on the same site. RESULTS: The differences in peak torque and total work among the three conditions were nonsignificant (p>0.05). Additionally, applying KT to the thigh muscles did not decrease or increase the performance of non injured healthy soccer players (p>0.05). CONCLUSION: KT does not lead to beneficial outcomes of muscle performance in healthy young soccer players.

NO EFFECT OF KINESIOLOGY TAPE ON PASSIVE TENSION, STRENGTH OR QUADRICEPS MUSCLE ACTIVATION OF DURING MAXIMAL VOLUNTARY ISOMETRIC CONTRACTIONS IN RESISTANCE TRAINED MEN.

BACKGROUND: Kinesiology Tape (KT) is widely used in sports rehabilitation and by those performing physical activity, however, there is no consensus in the scientific literature about its effectiveness on performance, strength or muscle activation.Purpose: The purpose of this study was to measure the acute effects of KT in static rest, and during knee extension maximal voluntary isometric contraction (MVIC) performance in resistance trained men.Study Design: Observational, descriptive, comparative. METHODS: Eighteen young, healthy, trained males (age: 25 ± 6 years, height: 176.0 ± 5 cm, and mass: 81.8 ± 8.0 kg) volunteered to participate. Initially, they were in a relaxed sitting position of 90 degrees knee flexion with their limb supported by the machine lever arm to measure passive tension of the tissues of the knee joint. Then, they performed three MVIC trials of five seconds each with a three-minute rest between trials, in four randomized experimental conditions, with 10-min rest between conditions: (a) control, no taping; (b) Knee Sleeve; (c) KT; and (d) sham. During all MVICs, peak force, impulse, and muscle activation of the vastus lateralis (integrated electromyography [IEMG] and median frequency) were measured. RESULTS: Repeated measures ANOVAs revealed no statistical differences between conditions for passive tension (p > 0.05), peak force (p > 0.05), impulse (p > 0.05), IEMG (p > 0.05), or median frequency (p > 0.05). CONCLUSION: KT does not influence passive tension during static position at 90 degrees of knee flexion. KT does not affect quadriceps activation or force production during a maximal voluntary isometric contraction in the same position. LEVEL OF EVIDENCE: 3a.

Greater volumes are required to reduce muscle performance in well-trained individuals / Grandes volumes são necessários para reduzir o desempenho muscular em indivíduos bem treinados

Abstract A specific drop jumps (DJs) protocol (using 100 jumps) has been largely used to induce muscle damage. However, it failed to show relevant drop in performance in well-trained individuals. Trained subjects may require a protocol with greater volume to induce decrease of muscle performance. The aim of this study was to assess muscle performance after two DJs damaging protocols with different volumes in well-trained individuals. Eighteen strength and/or power-trained males (4.92 ± 2.78 years of training experience) were randomly assigned into one of two groups: DJ100 (five sets of 20 DJs) or DJ140 (seven sets of 20 DJs), with 2-min of rest interval. DJs were performed from a 60-cm box. After landing, the volunteers performed a maximal vertical rebound jump. Muscle swelling increased significantly on both DJ100 and DJ140 (p < 0.001). Maximal isometric torque (MIT) decreased significantly on both DJ100 (p = 0.005) and DJ140 (p < 0.001). MIT showed no between-group difference on pre-assessment (p = 0.815). However, on post-assessment, MIT was significantly lower on DJ140 than DJ100 (p = 0.043). Countermovement jump (CMJ) decreased significantly on DJ140 (p = 0.001), but not on DJ100 (p = 0.802). There was no between-group difference on pre-assessment (p = 0.978). However, on post-assessment, CMJ was significantly lower on DJ140 than DJ100 (p = 0.038). DJ140 induced greater drop in isometric strength than DJ100 and only DJ140 significantly reduced jump performance. These results demonstrated that well-trained individuals require a great volume of DJs to reduce substantially muscle performance.

Resumo Um protocolo específico de Drop Jumps (DJs), com 100 saltos, tem sido amplamente utilizado para induzir o dano muscular. Entretanto, este protocolo tem falhado em mostrar uma queda relevante em indivíduos treinados. Objetivou-se avaliar o desempenho muscular após dois protocolos de DJs com diferentes volumes em indivíduos treinados. Dezoito homens treinados em força e/ou potência (4,92 ± 2,78 anos de treinamento) foram aleatoriamente designados em um dos dois grupos: DJ100 (cinco séries de 20 DJs) ou DJ140 (sete séries de 20 DJs), com 2 minutos entre as séries. Os DJs foram executados de uma caixa de 60 cm de altura. Após a aterrisagem, os voluntários executaram um salto vertical máximo. O inchaço muscular aumentou significativamente em ambos os grupos (p < 0,001). O torque isométrico máximo (TIM) reduziu significativamente tanto no DJ100 (p = 0,005) quanto no DJ140 (p < 0,001). O TIM não apresentou diferenças entre grupos no momento pré (p = 0,815). Entretanto, no momento pós, o TIM foi significativamente inferior no DJ140 em relação ao DJ100 (p = 0,043). O salto com contra movimento (SCM) reduziu significativamente no DJ140 (p = 0,001), mas não no DJ100 (p = 0,802). No momento pós, o SCM foi significativamente inferior no DJ140 em relação ao DJ100. O DJ140 induziu uma queda maior na força isométrica em relação do DJ100, e somente o DJ140 reduziu significativamente o desempenho no salto. Esses resultados demonstraram que indivíduos bem treinados requerem um grande volume DJs para reduzir substancialmente o desempenho muscular.

Photobiomodulation (PBM) therapy at 904 nm mitigates effects of exercise-induced skeletal muscle fatigue in young women.

Muscle fatigue is a process influenced by several mechanisms such as concentration of metabolic substrates, changes in blood flow, and increases in reactive oxygen species that impair contractile muscle function. In this context, photobiomodulation has been investigated for preventing muscle fatigue, with reports of positive effects on muscle performance. This study aimed to investigate the effects of 904-nm LASER photobiomodulation on rectus femoris muscle performance in young women. Eighteen young women participated in a randomized, participant and assessor-blinded crossover trial with placebo control. Active LASER (904 nm, 60 mW, 250 Hz, 3.6 J per diode, total dose of 129.6 J) intervention was applied prior to an isokinetic fatigue protocol consisting of a set of 60 concentric quadricep contractions at a constant dynamometer angular velocity of 180°/s. Compared to placebo, LASER photobiomodulation significantly reduced muscle fatigue across a range of indicators including reduced ratings of perceived exertion (P = 0.0139), and increased electromyographic fatigue index (EFI) (P = 0.005). The isokinetic dynamometer performance analysis demonstrated that LASER photobiomodulation increased peak torque (P = 0.04), time to peak torque (P = 0.042), total work (P = 0.032), average power (P = 0.0007), and average peak torque (P = 0.019) between both experimental conditions. No significant difference was observed for work fatigue index (P = 0.29) or for lactate concentration (P > 0.05). Photobiomodulation at 904 nm was effective in reducing fatigue levels and increasing muscle performance in young active women but had no effect on lactate levels.

Myoeletric indices of fatigue adopting different rest intervals during leg press sets.

INTRODUCTION: The purpose of this study was to examine the acute effect of different rest intervals between multiple sets of the 45° angled leg press exercise (LP45) on surface electromyographic (SEMG) spectral and amplitude indices of fatigue. METHODS: Fifteen recreationally trained females performed three protocols in a randomized crossover design; each consisting of four sets of 10 repetitions with 1 (P1), 3 (P3), or 5 (P5) minute rest intervals between sets. Each set was performed with 70% of the LP45 ten-repetition maximum load. The SEMG data for biceps femoris (BF), vastus lateralis (VL), vastus medialis (VM), and rectus femoris (RF) muscles was then evaluated. RESULTS: The SEMG amplitude change in the time coefficient (CRMS) and spectral fatigue index (Cf5) indicated higher levels of fatigue for all muscles evaluated during the P3 protocol versus the P1 and P5 protocols (p ≤ 0.05), respectively. The RF and VL muscles showed greater fatigue levels by the second and third sets; whereas, greater fatigue was shown in the VM and BF muscles by the fourth set (p ≤ 0.05). CONCLUSIONS: A three-minute rest interval between sets might represent a neuromuscular window between a fatigue stated and fully recovered state in the context of neural activation. Moreover, a three minute rest interval between sets might allow for consistent recruitment of high threshold motor units over multiple sets, and thus promote a more effective stimulus for strength gains.

Comparison between parameters of muscle performance and inflammatory biomarkers of non-sarcopenic and sarcopenic elderly women.

BACKGROUND: Sarcopenia is a multifactorial geriatric syndrome with complex interrelationships. Increased plasma levels of inflammatory mediators increase the catabolic stimuli of the musculature, thereby causing a decrease in mass and muscular function. OBJECTIVE: The objective of this study was to compare the performance of the knee extensors test (by isokinetic dynamometer) and plasma levels of interleukin-6 (IL-6) and soluble receptors of tumor necrosis factor alpha (sTNFR1) between sarcopenics and non-sarcopenics community-dwelling elderly women residents of Brazil. MATERIAL AND METHODS: The diagnosis of sarcopenia included measurements of body composition (by densitometry with dual energy source of X-ray), handgrip strength (by Jamar® dynamometer), and the usual gait velocity according to the recommendations of the European Working Group on Sarcopenia in Older People. In both sarcopenics and non-sarcopenics elderly women, we evaluated the muscle function by knee extensors test (using an isokinetic dynamometer Byodex System 4 Pro®) at angular speeds of 60°/s and 180°/s) and also we evaluated the plasma concentrations of IL-6 and sTNFR1. Comparisons of muscle performance between groups were carried out using mixed factorial ANOVA with post hoc Bonferroni test; sTNFR1 and IL-6 variables were analyzed by applying Mann-Whitney U test. RESULTS: Statistical differences were observed between groups regarding muscle power (P=0.01), total work adjusted to body weight (P=0.01) at a rate of 180°/s, and plasma levels of sTNFR1 (P=0.01). CONCLUSION: Sarcopenic elder women showed lower performance of the lower limbs, especially at a higher speed, predisposing these older women to greater vulnerability in functional activities that require agility and postural stability. Plasma levels of sTNFR1 were higher for non-sarcopenics elderlies. However, due to the observational nature of the study, it was impossible to infer causality among the variables surveyed.

Phototherapy for Improvement of Performance and Exercise Recovery: Comparison of 3 Commercially Available Devices.

CONTEXT: Recent studies suggest the prophylactic use of low-powered laser/light has ergogenic effects on athletic performance and postactivity recovery. Manufacturers of high-powered lasers/light devices claim that these can produce the same clinical benefits with increased power and decreased irradiation time; however, research with high-powered lasers is lacking. OBJECTIVE: To evaluate the magnitude of observed phototherapeutic effects with 3 commercially available devices. DESIGN: Randomized double-blind placebo-controlled study. SETTING: Laboratory. PATIENTS OR OTHER PARTICIPANTS: Forty healthy untrained male participants. INTERVENTION(S): Participants were randomized into 4 groups: placebo, high-powered continuous laser/light, low-powered continuous laser/light, or low-powered pulsed laser/light (comprising both lasers and light-emitting diodes). A single dose of 180 J or placebo was applied to the quadriceps. MAIN OUTCOME MEASURE(S): Maximum voluntary contraction, delayed-onset muscle soreness (DOMS), and creatine kinase (CK) activity from baseline to 96 hours after the eccentric exercise protocol. RESULTS: Maximum voluntary contraction was maintained in the low-powered pulsed laser/light group compared with placebo and high-powered continuous laser/light groups in all time points (P < .05). Low-powered pulsed laser/light demonstrated less DOMS than all groups at all time points (P < .05). High-powered continuous laser/light did not demonstrate any positive effects on maximum voluntary contraction, CK activity, or DOMS compared with any group at any time point. Creatine kinase activity was decreased in low-powered pulsed laser/light compared with placebo (P < .05) and high-powered continuous laser/light (P < .05) at all time points. High-powered continuous laser/light resulted in increased CK activity compared with placebo from 1 to 24 hours (P < .05). CONCLUSIONS: Low-powered pulsed laser/light demonstrated better results than either low-powered continuous laser/light or high-powered continuous laser/light in all outcome measures when compared with placebo. The increase in CK activity using the high-powered continuous laser/light compared with placebo warrants further research to investigate its effect on other factors related to muscle damage.

Comparison of elbow flexor isokinetic peak torque and fatigue index between men and women of different training level.

The purpose of the study was to compare elbow flexion peak torque (PT) and fatigue index (FI) during isokinetic concentric contractions in men and women with different training levels. Sixty-eight young men and women were divided into four groups: resistance trained men (RTM), non-resistance trained men (NRTM), resistance trained women (RTW) and non- resistance trained women (NRTW). Participants performed two tests on an isokinetic dynamometer, one to evaluate PT and one to evaluate FI. Significant interactions were found for sex and resistance training status with both PT and FI. In general, resistance-trained subjects had higher PT, and women showed lower PT than men. PT values were 67.12 ± 9.93 N·m for RTM, 49.9 ± 8.5 N·m for NRTM, 41.84 ± 7.52 N·m for RTW, and 26.05 ± 3.34 N·m for NRTW. Separate analysis revealed that RTM had higher PT than all other groups. However, FI was higher for NRTM than for RTM and NRTW and no difference was found between RTM and NRTW. FI was 37.86 ± 10.89 % for RTW, 45.74 ± 13.17 % for NTRW, 45.89 ± 8.24 % for RTM, and 51.92 ± 4.5 % for NRTM. Women produce lower PT, and have a higher fatigue tolerance than men of similar training status. Considering that women showed to be more resistant to fatigue than men, women can manipulate training variables differently from men, such as, including more repetitions at the same relative load or using higher relative loads at the same number of repetitions.

Light-emitting diode therapy in exercise-trained mice increases muscle performance, cytochrome c oxidase activity, ATP and cell proliferation [J. Biophotonics 8, No. 9, 740-754 (2015)].

In the article by C. Ferraresi et al. (DOI: http://dx.doi.org/10.1002/jbio.201400087), published in J. Biophotonics 8, 740-754 (2015), a statement regarding the approval of some data the authors used is incorrect. This erratum is published to rectify this.

Isokinetic performance of knee flexor and extensor muscles in community-dwelling elderly women / Desempenho dos músculos flexores e extensores de joelho de idosas da comunidade no dinamômetro isocinético

AbstractIntroduction The isokinetic dynamometer enables accurate assessment of muscle function. In Brazil, few studies have assessed the isokinetic muscle performance in older adults making interpretation and comparison of results with other studies.Objectives To conduct a descriptive analysis of the performance of the muscle flexor and extensor muscles of the knee joint in elderly community and compare the performance between the age groups 65-74 years and 75 years or more.Methods This is a cross sectional observational study with a convenience sample of 229 elderly community. For the analysis of muscle performance was used isokinetic dynamometer (Biodex System 3 Pro™) in the angular velocities of 60 °/s and 180 °/s. The variables evaluated were peak torque, peak torque normalized by body weight, total work normalized by body mass, total work, average power and agonist/antagonist ratio. Descriptive analysis was used to characterize the sample. For comparison between age groups was used Student's t-test with α = 0.05.Results The elderly women with older age showed a statistically significant decrease in most of the variables (p < 0.05) except for the agonist and antagonist knee (p = 0.398).Conclusions The isokinetic was a sensitive tool to characterize the modifications caused by aging on muscle function. Elderly with results below the lower limits of the confidence intervals for all variables certainly has a decreased strength for the age group evaluated and must be addressed therapeutically. The results can be used as a benchmark in clinical practice and future research.

ResumoIntrodução O dinamômetro isocinético possibilita a avaliação acurada da função muscular. No Brasil, poucos estudos avaliaram o desempenho muscular isocinético em idosos, dificultando a interpretação e comparação dos resultados com outros estudos.Objetivos Realizar uma análise descritiva do desempenho muscular dos músculos flexores e extensores da articulação do joelho de idosas da comunidade e comparar o desempenho entre as faixas etárias de 65 a 74 anos e 75 anos ou mais.Métodos Trata-se de um estudo observacional transversal, com uma amostra de conveniência com 229 idosas da comunidade. Para a análise do desempenho muscular foi utilizado o dinamômetro isocinético (Biodex System 3 Pro®) nas velocidades angulares de 60 °/s e 180 °/s. As variáveis avaliadas foram o pico torque, pico de torque normalizado pela massa corporal, trabalho normalizado pela massa corporal, trabalho total, potência e a relação agonista/antagonista. Foi utilizada análise descritiva para caracterização da amostra. Para comparação entre as faixas etárias foi usado o teste-t de Student considerando α = 0,05.Resultados As idosas com idade mais avançada apresentaram um decréscimo estatisticamente significativo na maioria das variáveis analisadas (p < 0,05) com exceção da relação agonista e antagonista do joelho (p = 0,398).Conclusão O dinamômetro isocinético foi um instrumento sensível para caracterizar as modificações ocasionadas pelo envelhecimento na função muscular. Idosas com resultados abaixo dos limites inferiores dos intervalos de confiança para as variáveis pesquisadas apresentam uma força diminuída para a faixa etária avaliada e devem ser abordadas terapeuticamente. Os resultados podem ser utilizados como parâmetro de comparação na prática clínica e em futuras pesquisas.