Exercise-induced muscle damage: mechanism, assessment and nutritional factors to accelerate recovery

Kinetics of recovery and normalization of running biomechanics following aerobic-based exercise-induced muscle damage in recreational male runners

OBJECTIVES

The study aimed to examine the effects of exercise-induced muscle damage on running kinetics.

DESIGN

Twenty-six adult recreational male runners performed 60 min of downhill running (-10 %) at 65 % of maximal heart rate. Running gait changes, systemic and localized muscle damage markers were assessed pre - and post-exercise induced muscle damage protocol.

METHODS

Running gait was analyzed using a 3D treadmill at baseline, immediately post, 24 h, and 48 h to determine changes in running pressure sway and vertical ground reaction forces. Blood markers, subjective pain perception, and magnetic resonance imaging utilizing T2 relaxation time of the thigh muscles assessed systemic and localized damage. Linear mixed-effects models examined changes over time.

RESULTS

Significant decreases were found in the left leg's first (-454.0 to -396.1, P < 0.05) and second (-532.8 to -498.2, P < 0.05) VGRF peaks across all time points compared to baseline. The right leg showed reductions in the first vertical ground reaction forced peak at immediately post (-348.4, P = 0.036) and the second peak at immediately post and 24 h (-467.4 and -396.8, P < 0.05). Creatine kinase increased significantly (P < 0.001) at 24 h and 48 h compared to baseline. The anterior thigh muscle compartment showed significant (P < 0.05) increases in mean T2 values 1 h following exercise protocol remained elevated up to 48 h. Negative correlations were identified between running biomechanics to local and systemic muscle damage markers.

CONCLUSIONS

Running biomechanics remained impaired for up to 48 h following exercise induced muscle damage and correlated with markers of muscle damage using magnetic resonance imaging.

The effect of repetitive exercise on tensile changes in the infraspinatus muscle evaluated with ultrasound elastography

BACKGROUND

The ability to identify muscle strain accurately is a critical aspect in managing exercise-induced muscle damage. Using differences in muscle stiffness as a proxy for muscle damage and recovery can better inform the decision to continue exercise versus pursue recovery.

HYPOTHESIS/PURPOSE

To identify changes in rotator cuff stiffness after a single bout of exercise as measured by ultrasound elastography.

STUDY DESIGN

10 healthy subjects, average age of 23.7, were enrolled in this prospective interventional trial. Each subject had a baseline scan then completed a standardized exercise program followed by another scan and daily evaluations until the results returned to within 10% of baseline.

METHODS

Elastography measurements were collected around the infraspinatus tendon, and the deltoid was used as a baseline standard.

STATISTICAL ANALYSIS USED

Summary statistics, t-test, and regression analysis were completed for the data.

RESULTS

Average strain was 0.5 at baseline, 0.7 immediately post-exercise, 0.6 on follow-up day 1, and 0.4 on follow-up day 2. There were statically significant differences between every timepoint. baseline-post 0.24, (p < 0.0001), post-day1 (decrease of 0.14, p < 0.0001), day1-day2 (decrease of 0.15, p < 0.0001), and BL-day2 (decrease of 0.05, p < 0.005).

CONCLUSIONS

These results demonstrate that the infraspinatus muscle stiffness increases immediately after exercise and takes up to 48 h to return to within 10% of baseline. We also found that at day 2 there continued to be an overcorrection with the infraspinatus remaining softer at this time point.

Effects of Carotenoid Supplementation on Exercise-Induced Oxidative Stress: A Systematic Review and Meta-Analysis of Randomized Clinical Trials

OBJECTIVE

This study aims to investigate the potential effects of carotenoid supplementation on mitigating exercise-induced oxidative stress and to provide guidance for future research.

METHODS

We conducted a systematic review and meta-analysis using Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. We searched multiple databases from inception to August 2024 for randomized clinical trials investigating the effects of carotenoid supplementation on biomarkers of oxidative stress, inflammatory markers, antioxidant levels, and metabolic parameters in the context of exercise-induced oxidative stress. The search terms included "carotenoids," "supplementation," "exercise," "oxidative stress," "inflammation," "antioxidants," "metabolic parameters," and their synonyms. Two reviewers independently extracted study data, with disagreements resolved by a third reviewer. Quality was assessed by the Cochrane risk-of-bias method. Random and fixed effects models were used for the analysis of standard mean differences (SMD) or weighted mean differences (MDs) with 95% confidence intervals (CI).

RESULTS

A total of 12 studies were included in the final analysis. Carotenoid supplementation led to significant effects in assessing oxidative stress induced by exercise (overall oxidative stress: SMD = -0.55, 95% CI [-1.04, -0.06]; malondialdehyde: MD = -0.05, 95% CI [-0.09,-0.02]; total antioxidant capacity: MD = 0.03, 95% CI [0.02, 0.03]; 8-isoprostane: MD = -35.70, 95% CI [-59.32, -12.09]; lipid peroxide: SMD = -1.07, 95% CI [-1.94, -0.20]; and nitric oxide: MD = -8.07, 95% CI [-12.54,-3.59]), inflammatory markers (inflammatory levels: SMD = 1.63, 95% CI [0.81, 2.46]; interleukin levels: SMD = 1.54, 95% CI [0.69, 2.40]; and C-reactive protein: MD = 4.56, 95% CI [0.97, 8.14]), antioxidant levels (SMD = 0.84, 95% CI [0.14, 1.53]), and metabolic parameters (energy expenditure: SMD = -0.52, 95% CI [-0.78, -0.26]; p < .05).

CONCLUSION

Carotenoid supplementation appears to attenuate exercise-induced oxidative stress and the inflammatory response and improve antioxidant levels and metabolic capabilities. However, these results may be influenced by participant variability or methodological differences. Further research with larger sample sizes, longer supplementation periods, higher doses, and carotenoid bioavailability is needed to confirm these findings.

Exercise therapy: an effective approach to mitigate the risk of cancer metastasis

Cancer metastasis is a primary contributor to cancer-related mortality, and mitigating the risk of metastasis has emerged as a central concern in oncology research. In recent years, exercise therapy, as a non-pharmacological intervention, has received considerable attention for its ability to enhance patients' quality of life and prognosis. Exercise significantly inhibits cancer spread, diminishes cancer risk, and improves therapy outcomes. Nonetheless, the exact mechanisms via which exercise inhibits the dissemination and metastasis of cancer cells are not fully elucidated. This review seeks to examine the mechanisms and prospective research avenues of exercise treatment in mitigating the risk of cancer metastasis. Moreover, it methodically examines pertinent clinical and scientific data, along with the efficacy of exercise therapies in real-world applications. The evaluation moreover suggests future research avenues, including a more profound exploration of mechanisms, the augmentation of clinical trials, the advancement of personalized and precision exercise therapy, and enhanced multidisciplinary collaboration. Exercise therapy shows significant potential in mitigating the risk of cancer metastasis, and its incorporation into holistic cancer treatment frameworks is advised to improve patients' general health and prognostic results.

Effect of Metabolic Stress to High-Load Exercise on Muscle Damage, Inflammatory and Hormonal Responses

To assess the impact of metabolic stress on blood lactate, muscle damage, inflammatory and hormonal responses following a high-load (70% maximum) strength training session, we compared two methods with a similar number of repetitions but that differed by their metabolic demand: the 3/7 method consisting in two series of five sets of an increasing number of repetitions (3 to 7) with a short inter-set interval (15 s) and the 8 × 6 method that comprises eight sets of six repetitions with a longer inter-set interval (2.5 min). Blood concentrations in lactate, creatine kinase (CK), myoglobin (MB), interleukine-6 (IL-6), leukocytes, growth hormone (GH), insulin-like growth factor-1 (IGF-1) and cortisol were determined before and after each session. Lactate concentration increased more (11.9 vs. 3.1 mmol/L; p < 0.001) for the 3/7 method whereas CK and MB concentrations were augmented similarly (p > 0.05) for both methods. Inflammatory markers (leukocytes and IL-6) increased (p < 0.01) more after the 3/7 method. GH and cortisol concentrations also increased more (p < 0.001) after the 3/7 method with no difference in IGF-1 concentrations between methods. Positive associations were found between the change in lactate and changes in IL-6 (r2 = 0.47; p < 0.01), GH (r2 = 0.58; p < 0.001) and cortisol (r2 = 0.61; p < 0.001) concentrations. In conclusion, the greater lactate accumulation induced by short inter-set intervals during a high-load training session is associated with enhanced inflammatory and hormonal responses, suggesting that metabolic stress might contribute to the greater adaptative response previously observed with this method.

The Effect of Omega-3 on Mitigating Exercise-Induced Muscle Damage

Exercise-induced muscle damage (EIMD) refers to muscle injuries following exercises involving repetitive eccentric muscle contractions. The resultant inflammation and muscle protein leakage into the circulation lead to muscle pain and strength deficit, compromising athletic performance. This narrative review summarizes the current evidence on the effect and mechanism of omega-3 polyunsaturated fatty acids (n-3 PUFA) in potentially mitigating EIMD. Several studies suggested n-3 PUFA's role in alleviating delayed-onset muscle soreness, particularly in untrained individuals and those receiving higher doses of continuous supplementation. However, its impact on muscle strength attenuation and the reduction of performance post-exercise remains inconclusive. Also unclear are n-3 PUFA's effects on the reduction of circulating pro-inflammatory substances and muscle proteins. One of the possible mechanisms is its anti-inflammatory property, which involves its ability to incorporate into cell membranes and displace prostaglandin precursor. n-3 PUFA also decreases cyclooxygenase production and can be converted into specialized pro-resolving mediators (SPMs), further reducing inflammation. Moreover, n-3 PUFA's incorporation into cell membranes alters cell membrane properties, diminishing protein release during muscle breakdown. n-3 PUFA exhibits analgesic effects through SPM-induced modulation of receptors and ion channels, reducing both peripheral and central sensitization. n-3 PUFA also diminishes mitochondrial free radical production and accelerates nerve conduction, thereby improving voluntary muscle activation.

Effects of 12-week whole-body vibration training versus resistance training in older people with sarcopenia

Sarcopenia is a syndrome commonly found in older people. The aim of this study was to evaluate the effects of whole-body vibration training (WBVT) and resistance training (RT) on body composition, muscle strength, physical performance and blood biomarkers in older people with sarcopenia. We conducted a 12-week, 3-times-weekly assessor-blinded, randomized controlled trial of 27 older people with sarcopenia aged ≥ 65 years. Subjects were randomized into WBVT group (n = 14) and RT group (n = 13). The primary outcome was knee extension strength (KES). Secondary outcomes were body composition [body weight, body mass index (BMI), percentage of body fat (PBF), and appendicular skeletal muscle mass index (ASMI)], muscle strength [handgrip strength (HS)], physical performance [gait speed (GS), 5-time chair stand test (5CST), and short physical performance battery (SPPB)], blood biomarkers (inflammatory factors, hormones, growth factors, and muscle injury biomarker), and quality of life questionnaire [medical outcomes study short-form 36 (SF-36)]. After 12-week intervention, in the WBVT group, we observed significant improvements in body composition (weight, BMI, PBF and ASMI), muscle strength (KES), physical performance (GS, SPPB and 5CST), blood biomarkers [insulin-like growth factor 1 (IGF-1), growth hormone, follistatin (FST) and creatine kinase (CK)] and quality of life. In the RT group, we observed significant improvements in body composition (weight, BMI and PBF), muscle strength (KES), physical performance (GS and SPPB), blood biomarkers (growth hormone, FST and CK) and quality of life. Between-group comparisons were only significant for KES (P = 0.007) and the role-physical (RP) dimension of the SF-36 (P = 0.007). WBVT and RT both improved the physical condition of older people with sarcopenia. RT excelled in muscle strength, but WBVT offered an alternative for those with restrictions. WBVT's low risk and flexibility suited diverse conditions, providing a new rehabilitation option for patients with sarcopenia.

The Influence of Caffeine on Tolerance to Sport-Specific High-Intensity Exercise in Young Elite Soccer Players

BACKGROUND

Modern elite football places extremely high demands on the athlete's body, so it is of practical interest to study the effect of various dietary supplements on load tolerance and postexercise recovery. Furthermore, there is a lack of research on the effects of caffeine on key measures of load tolerance in football such as delayed-onset muscle soreness (DOMS), rate of perceived exertion (RPE) and heart rate (HR) at different time points after the exercise.

METHODS

54 young players aged 15-17 years from a leading Russian football academy took part in a randomised trial using the balanced placebo design. They were divided into 4 groups: 1 - told caffeine/given caffeine, 2 - told caffeine/given placebo, 3 - told placebo/given placebo and 4 - told placebo/given caffeine. All participants consumed two capsules 60 min before testing, each containing 200 mg of caffeine or placebo. Sprinting, counter-movement jump, change of direction run, dribbling, T-test and the repeated sprint ability test were used to create conditions for high-intensity sports-specific load. A visual analogue scale was used to assess the severity of muscle soreness. RPE was assessed using the Borg Rating of Perceived Exertion scale. HR immediately postexercise (HRpe), HR after 2 min of passive rest (HRrest) and recovery HR (HRrec = HRpe - HRrest) were obtained.

RESULTS

The data demonstrated that a single caffeine intake of 400 mg had no statistically significant effect on RPE (p = 0.948), HRpe (p = 0.698) or HRrec (p = 0.920) across the groups. Additionally, the severity of DOMS 24 h postexercise did not differ significantly between the groups (p = 0.077).

CONCLUSION

Acute caffeine ingestion does not affect the subjective and objective indicators of training load in young football players aged 15-17 years with low levels of anxiety and low levels of daily caffeine intake.

The effect of tart cherry juice (TCJ) supplementation on exercise-induced muscle damage (EIMD) in an athletic population

Introduction

This systematic review and meta-analysis quantified the effect of tart cherry juice (TCJ) supplementation on exercise-induced muscle damage (EIMD). Evidence supported TCJ's beneficial effects on muscular function and inflammatory biomarkers interleukin (IL)-6 and IL-8.

Method

PubMed, Scopus, and Web of Science were searched up to January 2024. Risk of bias was assessed using RevMan® software. Mean differences and 95% confidence intervals (CIs) of maximal voluntary isometric contraction (MVIC), inflammatory markers, creatine kinase (CK), and visual analog scale (VAS) score were pooled using fixed- or random-effect models. Heterogeneity was assessed using Chi-square or I 2 statistics.

Results

Ten trials were included in the analysis. TCJ supplementation significantly improved MVIC [weighted mean difference (WMD) = 9.13%, 95% CI (6.42-11.84), I 2 = 62.3%] and decreased IL-6 [WMD = -0.4 pg/ml, 95% CI (-0.68 to -0.11), I 2 = 62.2%] and IL-8 [WMD = -0.3 pg/ml, 95% CI (-0.6 to -0.0), I 2 = 46.3%]. No significant changes were found in CK, C-reactive protein, IL-1β, tumor necrosis factor-alpha, or VAS score. Dose-response analysis revealed a significant non-linear association between daily TCJ dose and MVIC effect size.

Conclusion

TCJ supplementation may improve muscle function and some inflammatory biomarkers in EIMD. Further high-quality studies with larger sample sizes are needed to determine TCJ's long-term effects.

Recycle, repair, recover: the role of autophagy in modulating skeletal muscle repair and post-exercise recovery

Skeletal muscle is a highly plastic tissue that can adapt relatively rapidly to a range of stimuli. In response to novel mechanical loading, e.g. unaccustomed resistance exercise, myofibers are disrupted and undergo a period of ultrastructural remodeling to regain full physiological function, normally within 7 days. The mechanisms that underpin this remodeling are believed to be a combination of cellular processes including ubiquitin-proteasome/calpain-mediated degradation, immune cell infiltration, and satellite cell proliferation/differentiation. A relatively understudied system that has the potential to be a significant contributing mechanism to repair and recovery is the autophagolysosomal system, an intracellular process that degrades damaged and redundant cellular components to provide constituent metabolites for the resynthesis of new organelles and cellular structures. This review summarizes our current understanding of the autophagolysosomal system in the context of skeletal muscle repair and recovery. In addition, we also provide hypothetical models of how this system may interact with other processes involved in skeletal muscle remodeling and provide avenues for future research to improve our understanding of autophagy in human skeletal muscle.

Impact of blood flow restriction intensity on pain perception and muscle recovery post-eccentric exercise

BACKGROUND

Delayed onset muscle soreness (DOMS) is a well-established phenomenon characterized by ultrastructural muscle damage that typically develops following unfamiliar or high-intensity exercise. DOMS manifests with a constellation of symptoms, including muscle tenderness, stiffness, edema, mechanical hyperalgesia, and a reduced range of joint motion. In recent years, the application of blood flow restriction (BFR) has garnered attention for its potential impact on DOMS.

OBJECTIVE

This study aimed to investigate the effects of different BFR intensities on biomechanical alterations induced by DOMS in healthy individuals.

DESIGN AND METHODS

Thirty participants were split into two groups receiving either 80% or 20% BFR applied during low-intensity resistance exercise following DOMS induction. Pain perception, pressure pain threshold, muscle biometric characteristics, and strength were assessed before DOMS, after DOMS, and following BFR application at 24, 48, and 72 h.

RESULTS

The 80% BFR group experienced faster reductions in pain perception compared to the 20% BFR group. Muscle strength recovery was also statistically faster in the 80% BFR group. No significant differences were observed between groups in muscle stiffness, flexibility, or other mechanical properties.

CONCLUSIONS

These findings suggest that BFR, particularly at higher intensities, may alleviate DOMS symptoms and accelerate muscle strength recovery. However, the lack of a control group and limitations in muscle property assessment warrant further research to definitively determine BFR's efficacy in managing DOMS.

The effect of eccentric arm cycling on muscle damage and injury-related biomarkers

PURPOSE

There is a scarcity of information regarding the effect of upper-body eccentric exercise on biomarkers of muscle damage. This study sought to investigate the effect of eccentric arm cycling on muscle damage [exercise-induced muscle damage (EIMD)].

METHOD

Ten subjects performed a 15 min eccentric arm cycling protocol (cadence 49 ± 7 rpm, power absorbed 248 ± 34 W). Maximal voluntary contraction (MVC) of the elbow flexors was evaluated at rest and at 5 min, 24 h, and 48 h post-exercise. In addition, blood samples were drawn at rest and thereafter at 30 min, 24 h, and 48 h intervals after exercise for quantification of creatine kinase (CK), myoglobin, lactate dehydrogenase (LDH) and endothelin (ET-1) concentrations. Delayed onset muscle soreness (DOMS) was assessed using a category ratio scale (0-10).

RESULTS

Myoglobin was increased from baseline at 30 min post-exercise (+114%, 46.08 ± 22.17 µg/L, p = 0.018). Individual peak values were higher than baseline values for CK (+72.8%, 204 ± 138 U/L, p = 0.046) and LDH (+17%, 3.3 ± 0.88 nmole/min/mL, p = 0.017), but not for ET-1 (+9%, 1.4 ± 0.48 pg/mL, p = 0.45). DOMS was reported at 24 h (median 4) and 48 h (median 4) post-exercise and MVC of the elbow flexors were reduced from baseline (216 ± 44 N) at 5 min (-34%, 147 ± 61 N, p < 0.001), 24 h (-17%, 181 ± 56 N, p = 0.005) and 48 h (-9%, 191 ± 54 N, p = 0.003).

CONCLUSION

Eccentric arm cycling incites EIMD with reduced MVC and elevation of myoglobin, CK and LDH.

Observation on the therapeutic effect of rolling the target muscle groups of lower limbs with foam rollers of different shore hardness on DOMS

OBJECTIVE

This experiment aims to explore how foam rollers of different Shore hardness affect DOMS, providing insights for sports therapy.

METHODS

Forty participants from Shanghai Sanda University who have no habit of strength training, no lower limb injury, and meet the health standards were selected to conduct three experiments under the conditions of no intervention, using a 50 Shore hardness foam roller, and using a 60 Shore hardness foam roller, respectively. Data were recorded before and after modeling, as well as 24, 48, and 72 hours later.

RESULTS

There were no significant differences in various indicators among the three groups of subjects before and immediately after DOMS modeling (P>0.05). Following intervention, the 60 Shore hardness foam roller significantly reduced DOMS pain (NRS score) compared to the 50 Shore hardness roller, improved knee flexion range of motion, and increased standing long jump distance (P<0.05).

CONCLUSIONS

The 60 Shore hardness foam roller is superior to the 50 Shore hardness foam roller in alleviating DOMS, improving joint range of motion, and enhancing athletic performance.

Comparing the Effects of Collagen Hydrolysate and Dairy Protein on Recovery from Eccentric Exercise: A Double Blind, Placebo-Controlled Study

BACKGROUND

Consuming collagen hydrolysate (CH) may improve symptoms of exercise-induced muscle damage (EIMD); however, its acute effects have not been compared to dairy protein (DP), the most commonly consumed form of protein supplement. Therefore, this study compared the effects of CH and DP on recovery from EIMD.

METHODS

Thirty-three males consumed either CH (n = 11) or DP (n = 11), containing 25 g of protein, or an isoenergetic placebo (n = 11) immediately post-exercise and once daily for three days. Indices of EIMD were measured before and 30 min and 24, 48, and 72 h after 30 min of downhill running on a -15% slope at 80% of VO2max speed.

RESULTS

Downhill running induced significant EIMD, with time effects (all p < 0.001) for the delayed onset of muscle soreness (visual analogue scale), countermovement jump height, isometric midthigh pull force, maximal voluntary isometric contraction force, running economy, and biomarkers of muscle damage (creatine kinase) and inflammation (interleukin-6, high-sensitivity C-reactive protein). However, no group or interaction effects (all p > 0.05) were observed for any of the outcome measures.

CONCLUSIONS

These findings suggest that the post-exercise consumption of CH or DP does not improve indices of EIMD during the acute recovery period in recreationally active males.

Hydrogen gas inhalation prior to high-intensity training reduces attenuation of nitric oxide bioavailability in male rugby players

Background

Inhalation of hydrogen gas (H2) as an antioxidant supplement may alleviate exercise-induced oxidative damage and protect post-exercise hydrogen peroxide signaling, which may help mediate beneficial exercise adaptation. The aims of this study were to determine the effects of H2 inhalation on plasma nitric oxide (NO) level and its synthesis precursor in professional athletes.

Methods

A randomized, placebo-controlled, double-blind, crossover trial was conducted with professional male rugby players for 3 weeks. Participants underwent 1 week of H2 supplementation and 1 week of placebo treatment prior to daily sessions of high-intensity exercise training, separated by 1 week of low-intensity training as a washout.

Results

Two-way (supplementation and time) repeated-measures analyses of variance showed that NO, L-arginine, and tetrahydrobiopterin levels in the H2 inhalation group were significantly higher than those in the placebo group after exercise (D6) and remained higher after 24 h of rest (D7). Levels of hydroxydeoxyguanosine and interleukin 6 were lower in the H2 inhalation week than in the placebo week on D6 and D7. In addition, total antioxidant levels were significantly higher with H2 inhalation than with placebo.

Significance

These results suggest that H2 inhalation helps to maintain NO signaling after exercise and to alleviate inflammation and oxidative stress induced by high-intensity exercise training in professional athletes.

Intensity and volume of physical exercise influence DOMS and skin temperature differently in healthy adults

It remains unclear whether exercises leading to different outcomes of delayed onset muscle soreness (DOMS) may also elicit different skin temperature responses. The aim of this study was to determine whether different intensities and volumes of a single-joint exercise influence the DOMS and skin temperature measurements differently in healthy adults. Thirty-nine men and women were randomly assigned to three groups performing different exercise of different intensities and volumes (Exhaustion, Fatigue, Submaximal) to induce DOMS in the biceps brachii. DOMS (numeric pain rate scale, NPRS), pressure pain threshold (PPT) and skin temperature (infrared thermography, IRT) were measured on exercise day and 48 h later. The different exercises resulted in lower PPT responses 48 h after exercise and different DOMS reported across the different groups. Skin temperature outcomes did not differ following the different protocols. We found an increased minimum skin temperature 48 h after exercise in groups performing more intense exercises, but such differences were found in both exercised and non-exercised arms. Differently of PPT outcomes, pain reported depended on exercise intensity, and skin temperature 48 h after exercise could not show acute exercise adaptations. Skin temperature responses are contingent upon the characteristics of the participants rather than exercise intensity.

Is Match Playing Time a Potential Tool for Managing Load in Women's Handball?

ABSTRACT

García-Sánchez, C, Navarro, RM, Nieto-Acevedo, R, and de la Rubia, A. Is match playing time a potential tool for managing load in women's handball? J Strength Cond Res 38(12): e769-e775, 2024-The aim of this study was to explore the external load experienced by female handball players according to the time played in official matches (≥40, <40, and ≤20 minutes) and in relation to playing positions (backs, pivots, and wings). Twenty-two female players from the Spanish second Division were monitored across 13 matches. Total distance covered, high-speed running distance (HSR), accelerations, decelerations, and PlayerLoad were collected in absolute and relative values using a local positioning system (WIMU PRO, Realtrack Systems SL, Almería, Spain). One-way ANOVA with partial eta-squared and Cohen's d were used to determine the differences between playing time groups and between playing positions. This study revealed that players with more match playing time had a higher absolute values in all external load variables ( p < 0.001; very large effects), except in HSR where only wings showed higher values according to the time played ( p < 0.001; very large effects). However, these differences between playing time groups disappear when the external load values were normalized according to the effective playing time ( p > 0.05). In relation to playing positions, wings covered more HSR/minutes than the other playing positions regardless of the playing time ( p < 0.05; large effects). In addition, backs performed more ACC/minutes than wings in the high playing time group and more than pivots in the low playing time group ( p < 0.05, moderate effects). In addition, backs performed more DEC/minutes than wings in the low playing time group ( p < 0.05, moderate effects). Therefore, handball coaches should consider the playing time as an effective tool to optimize the weekly load distribution.

Enhancing performance through biochemical monitoring and nutritional support in female weightlifters during pre-competition weight reduction: a randomized trial

OBJECTIVE

Weight reduction is a common practice among female weightlifters before competitions to qualify for specific weight classes. However, this process can adversely affect their physical performance and health. This study aimed to investigate the impact of physiological and biochemical monitoring and nutritional support on the competitive state of female weightlifters during the pre-competition weight reduction period.

METHODS

A randomized controlled trial was conducted with 28 female weightlifters from Sichuan Province, China, randomly assigned to the experimental group (n = 14) or the control group (n = 14). Both groups followed their regular training schedules. The experimental group received personalized nutritional monitoring and supplementation, including detailed assessments, dietary logs, weekly consultations, and targeted supplements based on biochemical indicators and training needs. The control group continued with their standard diet and training without additional interventions. Serum indicators, fatigue scales, and Pittsburgh Sleep Quality Index (PSQI) scores were monitored (a total of 5 tests).

RESULTS

The experimental group exhibited a significant reduction in creatine kinase levels by the fourth week compared to both baseline and the first week (p < 0.05), and maintained higher levels of testosterone, testosterone/cortisol ratio, and hemoglobin than the control group from the second week onwards (p < 0.05). Conversely, the control group showed an increase in creatine kinase and a decrease in testosterone and testosterone/cortisol ratio over the same period (p < 0.05). By the fourth week, the experimental group also reported lower fatigue and better sleep quality, as indicated by lower PSQI scores, compared to the control group (p < 0.001).

CONCLUSION

Personalized nutritional supplementation has an improving effect on biochemical indicators, fatigue, and sleep quality in female weightlifters during the pre-competition weight reduction period. Implementing biochemical monitoring and personalized nutritional support during this period is a key strategy for enhancing the competitive performance of female weightlifters.

6-week time-restricted eating improves body composition, maintains exercise performance, without exacerbating eating disorder in female DanceSport dancers

BACKGROUND

Despite the high risk of eating disorder (ED)-related attitudes and behaviors among female dancers, targeted scientific dietary regimens are currently inadequate. Time-restricted eating (TRE), a popular intermittent fasting protocol, has been shown to be effective in enhancing body composition and exercise performance in athletes. In this study, TRE was employed as a dietary regimen to improve body composition and exercise performance and address ED attitudes and behaviors in DanceSport dancers.

METHODS

Twenty female DanceSport dancers were recruited and divided into two groups: TRE (n = 10) and normal diet (ND) (n = 10). The TRE group consumed their self-selected necessary energy intake exclusively between 11 a.m. and 7 p.m. (utilizing a 16-hour fasting and 8-hour eating window) for 6 weeks, while the ND group maintained their regular dieting patterns. The consumption of water, black tea, or coffee without added sugar or milk was not restricted. Physical activity and calorie intake were systematically recorded during the TRE intervention. Body composition, aerobic and anaerobic performance, and ED attitudes and behaviors were assessed before and after the TRE intervention. The trial was registered in the Chinese Clinical Trial Registry under the identifier ChiCTR2200063780.

RESULTS

The fixed effects tests (p < 0.0001) and estimates for the intercept (p < 0.0001) of hunger level indicated a noticeable effect on the initial state of hunger during TRE. No significant differences were observed in ED attitudes or behaviors (p > 0.05). TRE resulted in a reduction in hip circumference (p = 0.039), fat mass (kg) (p = 0.0004), and body fat percentage (p = 0.0005), with no significant decrease in fat-free mass (p > 0.05). No significant improvement was observed in aerobic performance (p > 0.05). The average power (AP) (p = 0.01) and AP/Body weight ratio (p = 0.003) significantly increased. Additionally, the power drop decreased significantly (p = 0.019). Group-by-time interactions were observed for fat mass (kg) (p = 0.01), body fat percentage (p = 0.035), and AP/Body weight (p = 0.020).

CONCLUSION

TRE can be considered a feasible nutritional strategy for DanceSport dancers, facilitating improvements in body composition without compromising aerobic and anaerobic exercise performance or exacerbating ED attitudes and behaviors. Moreover, TRE may facilitate more favorable physiological adaptations, potentially contributing to improved exercise performance.

Physical Activity in young female outpatients with BORderline personality Disorder (PABORD): a study protocol for a randomized controlled trial (RCT)

BACKGROUND

Current treatments for mental disorders, like pharmacotherapy or psychological approaches, do not lead to full remission in all individuals. Physical activity (PA) is effective at improving psycho-physical health in major depressive and anxiety disorders. However, the efficacy of PA as an adjunctive treatment for borderline personality disorder (BPD) has not been studied. To date, there are no approved pharmacological treatments for this severe condition and limited accessibility to effective psychotherapeutic interventions. This study tests the efficacy of a structured PA programme as an additional treatment for BPD outpatients.

METHODS

The PABORD is a randomised controlled trial for female outpatients (18-40 years) with a BPD diagnosis. The intervention group (n = 32) will participate in a 12-week structured PA programme supervised by a sport medicine physician and preceded by three psychoeducation sessions on healthy eating habits. The control group (n = 32) will receive a 12-week psychoeducation programme on PA, diet, and health risks of a sedentary lifestyle for a total of 8 sessions. The study aims to determine if the PA intervention is superior to the control in reducing BPD symptoms. Secondary aims include improving PA levels and physical and psychological health. Assessments will be conducted at baseline, post-intervention, and 3 months post-intervention.

DISCUSSION

The structured PA programme is expected to outperform the control group in terms of health and PA outcomes at the end of the intervention. Repeated assessments will also help to identify psychosocial factors that influence PA maintenance. Findings will support the potential widespread implementation of PA programmes for BPD treatment.

TRIAL REGISTRATION

ClinicalTrials.gov NCT06461104. Registered on 6 June 2024 {2a}.

Acute cardiovascular responses of postmenopausal women to resistance training sessions differing in set configuration: A study protocol for a crossover trial

BACKGROUND

Resistance training is hardly recommended for postmenopausal women to counteract negative effects of hormonal changes. However, some concern exists about the marked hemodynamic responses caused by high-load resistance exercises. In this regard, studies on young, healthy, physically active individuals suggest that set configuration can modulate acute cardiovascular, metabolic, and cardiac autonomic responses caused by resistance training sessions, but this has not yet been explored in postmenopausal women.

METHODS

A sample of 60 physically active postmenopausal women (30 normotensive, 30 hypertensive) will participate in this crossover study. After a medical exam, ergometry, familiarization session, and two testing sessions, participants will complete three experimental sessions and one control session in a randomized order. Each experimental session includes 36 repetitions of four exercises (horizontal leg press, bench press, prone leg curl, and lat pull-down) differing in set configuration: 9 sets of 4 repetitions (i.e., 33% intensity of effort) with 45 s of inter-set recovery, 6 sets of 6 repetitions (50% intensity of effort) with 72 s, and 4 sets of 9 repetitions (75% intensity of effort) with 120 s; with 4 min rest between exercises. Before and immediately after each session, arterial stiffness, hemodynamic variables, cardiac autonomic modulation, baroreflex sensitivity, sympathetic vasomotor tone, and resting oxygen uptake will be evaluated. Furthermore, perceived effort, mechanical performance (e.g., power, velocity), heart rate, and lactatemia will be collected throughout sessions. The impact of set configuration on these variables will be analyzed, along with comparisons between normotensive and hypertensive women.

DISCUSSION

Cardiovascular responses to resistance exercise have been scarcely studied in females, particularly postmenopausal women. The results of this study will provide information about the modulating role of set structure on metabolic and cardiovascular responses of normotensive and hypertensive postmenopausal women to resistance training.

CLINICAL TRIAL REGISTRATION

NCT05544357 on 7 December 2022.

Exercise-specific adaptations in human skeletal muscle: Molecular mechanisms of making muscles fit and mighty

The mechanisms leading to a predominantly hypertrophied phenotype versus a predominantly oxidative phenotype, the hallmarks of resistance training (RT) or aerobic training (AT), respectively, are being unraveled. In humans, exposure of naïve persons to either AT or RT results in their skeletal muscle exhibiting generic 'exercise stress-related' signaling, transcription, and translation responses. However, with increasing engagement in AT or RT, the responses become refined, and the phenotype typically associated with each form of exercise emerges. Here, we review some of the mechanisms underpinning the adaptations of how muscles become, through AT, 'fit' and RT, 'mighty.' Much of our understanding of molecular exercise physiology has arisen from targeted analysis of post-translational modifications and measures of protein synthesis. Phosphorylation of specific residue sites has been a dominant focus, with canonical signaling pathways (AMPK and mTOR) studied extensively in the context of AT and RT, respectively. These alone, along with protein synthesis, have only begun to elucidate key differences in AT and RT signaling. Still, key yet uncharacterized differences exist in signaling and regulation of protein synthesis that drive unique adaptation to AT and RT. Omic studies are required to better understand the divergent relationship between exercise and phenotypic outcomes of training.

Pulsed Electromagnetic Field (PEMF) stimulation as an adjunct to exercise: a brief review

Pulsed Electromagnetic Field (PEMF) therapy is a non-invasive treatment that utilizes electromagnetic fields to stimulate and promote natural healing processes within the body. PEMF therapy works by emitting low-frequency electromagnetic pulses, which penetrate deep into tissues and cells, enhancing cellular function and health. PEMF applications are vast, ranging from enhancing recovery in athletes to supporting overall well-being in everyday individuals. PEMF therapy is increasingly recognized in the realm of sports and physical activity for its profound benefits in enhancing performance, accelerating recovery, and preventing injuries. By improving circulation, enhancing tissue oxygenation, and promoting the body's natural healing processes, PEMF therapy has become an invaluable tool in sports medicine, contributing to optimized physical health and prolonged athletic careers. In this review, we explore the effects of PEMF on exercise and the underlying physiological mechanisms.

Cell-free DNA kinetics in response to muscle-damaging exercise: A drop jump study

A significant increase in circulating cell-free DNA (cfDNA) occurs with physical exercise, which depends on the type of exertion and the duration. The aims of this study were as follows: (1) to investigate the time course of cfDNA and conventional markers of muscle damage from immediately after to 96 h after muscle-damaging exercise; and (2) to investigate the relationship between cfDNA and indicators of primary (low-frequency fatigue and maximal voluntary isometric contraction) and secondary (creatine kinase and delayed-onset muscle soreness) muscle damage in young healthy males. Fourteen participants (age, 22 ± 2 years; weight, 84.4 ± 11.2 kg; height, 184.0 ± 7.4 cm) performed 50 intermittent drop jumps at 20 s intervals. We measured cfDNA and creatine kinase concentrations, maximal voluntary isometric contraction torque, low-frequency fatigue and delayed-onset muscle soreness before and at several time points up to 96 h after exercise. Plasma cfDNA levels increased from immediately postexercise until 72 h postexercise (P < 0.01). Elevation of postexercise cfDNA was correlated with both more pronounced low-frequency fatigue (r = -0.52, P = 3.4 × 10-11) and delayed-onset muscle soreness (r = 0.32, P = 0.00019). Levels of cfDNA change in response to severe primary and secondary muscle damage after exercise. Levels of cfDNA exhibit a stronger correlation with variables related to primary muscle damage than to secondary muscle damage, suggesting that cfDNA is a more sensitive marker of acute loss of muscle function than of secondary inflammation or damaged muscle fibres.

Effects of acai supplementation (Euterpe precatoria Mart) on muscle recovery markers after jump protocol

The objective was to evaluate the effects of acai supplementation (AS) on markers of muscle damage. Twelve men participated in the 21-day study. All performed the damage protocol (DP) in two moments, separated by 7 days. The DP consisted of 10 sets of 10 CMJs, with a recovery of 1 min between sets. The AS was performed for 7 days with 40 g/day of dehydrated acai (GA) or placebo (GP). Blood parameters (CK, LDH and Trolox-equivalent antioxidant capacity - TEAC) were evaluated at 0 h and 24 h. Ultrasound images (VL, RF and GM), DOMS in lower limbs and isometric peak torque (IPT) of knee extensors and flexors were evaluated at 0 h, 24 h, 48 h and 72 h after DP. A time-treatment interaction was observed for TEAC (p = 0.01), in which the GA presented increases of 11% after 24 h. Similarly, time-treatment interaction was observed for knee flexors IPT (p = 0.02), where GA showed superior recovery after 24 h (GA = 108 ± 23 vs. GP = 92 ± 24 N∙m) and 72 h (GA = 113 ± 31 vs. GP = 98 ± 26 N∙m). No significance was observed in the fatigue index for knee extensors (p = 0.75) and flexors (p = 0.89), indicating similar fatigue in both situations. We concluded that AS increased the TEAC and promoted faster recovery of the knee flexors IPT when compared to GP.

Acute effects of Nordic hamstring exercise on hip and knee joints proprioception

BACKGROUND AND OBJECTIVES

Nordic Hamstring Exercise (NHE) is one of the best exercises proposed for injury prevention of hamstring muscles. However, its effects on lower extremity proprioception are unclear. The aim of this study was to investigate the immediate effects of a single bout of NHE on hip and knee joints' proprioception.

METHODS

Forty collegiate male soccer players participated in this study with a mean age of 22.85 ± 1.82 years and were randomized into either control (n = 20) or experimental (n = 20) groups. Each subject participated in pre-test measurements in which hip and knee active joints position sense (JPS) were assessed in standing and lying tasks using the image-capturing method. The experimental group then performed three sets of NHE with 10 repetitions in each set, while the control group rested for 10 min. Paired and independent t-tests were used for calculating the differences within and between groups on SPSS software, respectively. The level of significance was P ≤ 0.05.

RESULTS

Hip JPS in the lying task and knee JPS in both of the standing and lying tasks were impaired significantly after performing a single bout of NHE (P ≤ 0.05). However, the effects of this exercise on hip JPS in the standing task were not significant (P ≥ 0.05).

CONCLUSIONS

NHE performing with three sets of 10 repetitions can significantly impair hip and knee JPS immediately after exercise and reduce the proprioception acuity of the lower limbs. It is recommended to perform this exercise at a time rather than before training or match sessions.

Force-Time Characteristics of Repeated Bouts of Depth Jumps and the Effects of Compression Garments

No studies have reported ground reaction force (GRF) profiles of the repeated depth jump (DJ) protocols commonly used to study exercise-induced muscle damage. Furthermore, while compression garments (CG) may accelerate recovery from exercise-induced muscle damage, any effects on the repeated bout effect are unknown. Therefore, we investigated the GRF profiles of 2 repeated bouts of damage-inducing DJs and the effects of wearing CG for recovery. Nonresistance-trained males randomly received CG (n = 9) or placebo (n = 8) for 72 hours recovery, following 20 × 20 m sprints and 10 × 10 DJs from 0.6 m. Exercise was repeated after 14 days. Using a 3-way (set × bout × group) design, changes in GRF were assessed with analysis of variance and statistical parametric mapping. Jump height, reactive strength, peak, and mean propulsive forces declined between sets (P < .001). Vertical stiffness, contact time, force at zero velocity, and propulsive duration increased (P < .05). According to statistical parametric mapping, braking (17%-25% of the movement) and propulsive forces (58%-81%) declined (P < .05). During the repeated bout, peak propulsive force and duration increased (P < .05), while mean propulsive force (P < .05) and GRF from 59% to 73% declined (P < .001). A repeated bout of DJs differed in propulsive GRF, without changes to the eccentric phase, or effects from CG.

Effect of Spirulina Nigrita® Supplementation on Indices of Exercise-Induced Muscle Damage after Eccentric Protocol of Upper Limbs in Apparently Healthy Volunteers

Spirulina is a supplement with antioxidant and anti-inflammatory properties that may enhance performance and recovery after intense exercise. The present study aimed to investigate the effects of Spirulina Nigrita® on physical performance, and recovery markers after intense eccentric exercise in healthy moderately physically active volunteers. In a double-blind crossover design, participants were supplemented either with spirulina (42 mg Kg-1 BW per day) or a placebo for 15 days before conducting an eccentric exercise protocol using the non-dominant arm. A six-week washout period was required between conditions. Performance and mobility markers such as isometric peak torque (PTQ), ligament range of motion (ROM), and perceived muscle discomfort (VAS) were assessed and blood samples (CK, LDH) were obtained at 1, 24, 48, and 72 h post-exercise. No significant differences were noticed between the two conditions on any of the investigated markers, indicating that spirulina supplementation has no positive effect on isometric muscle performance or alleviation of exercise-induced muscle damage (EIMD) symptoms in the specific population.

Can pre-exercise photobiomodulation improve muscle endurance and promote recovery from muscle strength and injuries in people with different activity levels? A meta-analysis of randomized controlled trials

Photobiomodulation therapy (PBMT) was introduced as an ergogenic aid for sport performance in healthy individuals is still controversial. The main aim of this study is to assess the potential enhancements in muscle endurance and recovery from muscle strength and injuries mediated by PBMT among individuals exhibiting diverse activity levels. Randomized controlled trials (RCT) of PBMT interventions for healthy people (both trained and untrained individuals) exercising were searched (up to January 16, 2024) in four electronic databases: Web of Science, PubMed, Scopus and Embase. Primary outcome measures included muscle endurance, muscle strength and creatine kinase (CK) levels; secondary outcome measure included Lactate dehydrogenase (LDH) levels. Subgroup analyses based on physical activity levels were conducted for each outcome measure. Thirty-four RCTs were included based on the article inclusion and exclusion criteria. Statistical results showed that PBMT significantly improved muscle endurance (standardized mean difference [SMD] = 0.31, 95%CI 0.11, 0.51, p < 0.01), indicating a moderate effect size. It also facilitated the recovery of muscle strength (SMD = 0.24, 95%CI 0.10, 0.39, p < 0.01) and CK (mean difference [MD] = -77.56, 95%CI -112.67, -42.44, p < 0.01), indicating moderate and large effect sizes, respectively. Furthermore, pre-application of PBMT significantly improved muscle endurance, recovery of muscle strength and injuries in physically inactive individuals and athletes (p < 0.05), while there was no significant benefit for physically active individuals. Pre-application of PBMT improves muscle endurance and promotes recovery from muscle strength and injury (includes CK and LDH) in athletes and sedentary populations, indicating moderate to large effect sizes, but is ineffective in physically active populations. This may be due to the fact that physically active people engage in more resistance training, which leads to a decrease in the proportion of red muscle fibres, thus affecting photobiomodulation.

Reduction in systemic muscle stress markers after exercise-induced muscle damage following concurrent training and supplementation with specific collagen peptides - a randomized controlled trial

Introduction

Collagen peptide supplementation in conjunction with exercise has been shown to improve structural and functional adaptations of both muscles and the extracellular matrix. This study aimed to explore whether specific collagen peptide (SCP) supplementation combined with a concurrent training intervention can improve muscular stress after exercise-induced muscle damage, verified by reliable blood markers.

Methods

55 sedentary to moderately active males participating in a concurrent training (CT) intervention (3x/week) for 12 weeks were administered either 15 g of SCP or placebo (PLA) daily. Before (T1) and after the intervention (T2), 150 muscle-damaging drop jumps were performed. Blood samples were collected to measure creatine kinase (CK), lactate dehydrogenase (LDH), myoglobin (MYO) and high-sensitivity C-reactive protein (hsCRP) before, after, and at 2 h, 24 h and 48 h post exercise.

Results

A combination of concurrent training and SCP administration showed statistically significant interaction effects, implying a lower increase in the area under the curve (AUC) of MYO (p = 0.004, ηp2 = 0.184), CK (p = 0.01, ηp2 = 0.145) and LDH (p = 0.016, ηp2 = 0.133) in the SCP group. On closer examination, the absolute mean differences (ΔAUCs) showed statistical significance in MYO (p = 0.017, d = 0.771), CK (p = 0.039, d = 0.633) and LDH (p = 0.016, d = 0.764) by SCP supplementation.

Conclusion

In conclusion, 12 weeks of 15 g SCP supplementation combined with CT intervention reduced acute markers of exercise-induced muscle damage and improved post-exercise regenerative capacity, as evidenced by the altered post-exercise time course. The current findings indicate that SCP supplementation had a positive effect on the early phase of muscular recovery by either improving the structural integrity of the muscle and extracellular matrix during the training period or by accelerating membrane and cytoskeletal protein repair.

Clinical trial registration

https://www.clinicaltrials.gov/study/NCT05220371?cond=NCT05220371&rank=1, NCT05220371.

Recovery kinetics following sprint training: resisted versus unresisted sprints

PURPOSE

To determine the recovery kinetics of performance and exercise-induced muscle damage following different sprint-training protocols.

METHODS

In a crossover design, ten male and female athletes (20.6 ± 2.4 years) performed 2 × (3 × 20 m: 2 min rest) and 1× (3 × 30 m: 3 min rest) of: (a) unresisted sprints (UST), (b) resisted sprints with 10% of body mass (BM) load (RST10), (c) resisted sprints with 20% BM load (RST20), against a control trial (no-training).

RESULTS

Blood lactate (mmol/L) increased post-training versus pre-training in all sprint-training trials (6.7 ± 2.4 vs 1.2 ± 0.2, 5.6 ± 2.4 vs 1.3 ± 0.3, 7.3 ± 2.7 vs 1.2 ± 0.3, in UST, RST10, RST20, respectively), as did creatine kinase (U/L) 24 h, 48 h and 72 h post-training (UST: 251 ± 173, 238 ± 154, 209 ± 115 vs 155 ± 9, RST10: 252 ± 134, 240 ± 83, 218 ± 103 vs 164 ± 106; RST20: 237 ± 133, 323 ± 303, 262 ± 184 vs 179 ± 106, respectively). DOMS of knee-extensors (KE) and knee-flexors (KF) increased post-training up to 72 h in all sprint-training trials versus pre-training (ranging from 1.6 ± 1.3 to 3.8 ± 2.8 vs 1.0 ± 0, respectively). Eccentric torque (N m) of the KE of the non-dominant limb, decreased 24 h post-training versus pre-training in all sprint-training trials (UST: 249 ± 49 vs 266 ± 54; RST10: 229 ± 52 vs 273 ± 72; RST20: 253 ± 6 vs 262 ± 56), as did that of the KF of the dominant limb (UST: 135 ± 29 vs 144 ± 26; RST10: 130 ± 29 vs 140 ± 25; RST20: 139 ± 33 vs 142 ± 26). 10-m sprint-time (s) increased 48 h post-training versus pre-training (1.81 ± 0.15 vs 1.77 ± 0.11), and 30-m sprint-time increased 24 h, 48 h, 72 h post-training versus pre-training (4.35 ± 0.36, 4.40 ± 0.44, 4.33 ± 0.41 vs 4.21 ± 0.34, respectively), only in RST20.

CONCLUSIONS

Unresisted and resisted sprint-training induces prolonged reduction of muscle strength (24 h), and sprinting performance (72 h), associated with prolonged increase of DOMS and CK (72 h).

Recovery markers in elite climbers after the national boulder climbing championship

This study aimed to investigate recovery markers among elite climbers following the National Boulder Championship. We assessed maximum isometric hand grip strength (HS), forearm swelling (circumference), delayed soreness in forearm muscles, tiredness, and exercise readiness at several time points: pre-competition, immediately post-competition (within 4 min after their last effort), and 12, 24, 48, and 60 h post-competition. Maximum isometric hand grip strength decreased by 6.38 ± 1.32% (p = 0.006) post-12 h, returning to pre-competition values post-24 h (all p > 0.05). Forearm circumference (FC) increased 1.78 ± 1.77% (p < 0.001) post-competition, returning to pre-competition values post-12 h (all p > 0.05). Forearm pain (FP) increased post-competition (p = 0.002) and post-12 h (p < 0.001), returning to pre-competition values post-24 h (all p > 0.05). Tiredness increased post-competition (p < 0.001), post-12 h (p < 0.001), and post-24 h (p < 0.001), returning to pre-competition values post-48 h (all p > 0.05). Climbing readiness was reduced post-competition (p < 0.001), post-12 h (p < 0.001), post-24 h (p < 0.001), and post-48 h (p = 0.005), only returning to pre-competition values post-60 h (p = 0.189). Visual analysis of individual data pointed out a relatively small variability in the HS and FC markers, while FP, tiredness, and readiness exhibited larger individual variations. These findings indicate that different recovery patterns exist for the analyzed markers, suggesting that athletes may require up to 60 h after a competition to fully recover and regain their ability to face new competitive challenges.

Dynamic palmitoylation of STX11 controls injury-induced fatty acid uptake to promote muscle regeneration

Different types of cells uptake fatty acids in response to different stimuli or physiological conditions; however, little is known about context-specific regulation of fatty acid uptake. Here, we show that muscle injury induces fatty acid uptake in muscle stem cells (MuSCs) to promote their proliferation and muscle regeneration. In humans and mice, fatty acids are mobilized after muscle injury. Through CD36, fatty acids function as both fuels and growth signals to promote MuSC proliferation. Mechanistically, injury triggers the translocation of CD36 in MuSCs, which relies on dynamic palmitoylation of STX11. Palmitoylation facilitates the formation of STX11/SNAP23/VAMP4 SANRE complex, which stimulates the fusion of CD36- and STX11-containing vesicles. Restricting fatty acid supply, blocking fatty acid uptake, or inhibiting STX11 palmitoylation attenuates muscle regeneration in mice. Our studies have identified a critical role of fatty acids in muscle regeneration and shed light on context-specific regulation of fatty acid sensing and uptake.

Age-Associated Differences in Recovery from Exercise-Induced Muscle Damage

Understanding the intricate mechanisms governing the cellular response to resistance exercise is paramount for promoting healthy aging. This narrative review explored the age-related alterations in recovery from resistance exercise, focusing on the nuanced aspects of exercise-induced muscle damage in older adults. Due to the limited number of studies in older adults that attempt to delineate age differences in muscle discovery, we delve into the multifaceted cellular influences of chronic low-grade inflammation, modifications in the extracellular matrix, and the role of lipid mediators in shaping the recovery landscape in aging skeletal muscle. From our literature search, it is evident that aged muscle displays delayed, prolonged, and inefficient recovery. These changes can be attributed to anabolic resistance, the stiffening of the extracellular matrix, mitochondrial dysfunction, and unresolved inflammation as well as alterations in satellite cell function. Collectively, these age-related impairments may impact subsequent adaptations to resistance exercise. Insights gleaned from this exploration may inform targeted interventions aimed at enhancing the efficacy of resistance training programs tailored to the specific needs of older adults, ultimately fostering healthy aging and preserving functional independence.

A comparison of the effects of sheep's milk and cow's milk on recovery from eccentric exercise

Introduction

When consumed after eccentric exercise, cow's milk has been shown to improve recovery and alleviate symptoms of exercise induced muscle damage. Although currently less commercially available than cow's milk, sheep's milk may offer similar or greater benefits for recovery as it is higher in protein and energy; however, the effect of sheep's milk in any exercise context has not been explored. This study compared the effects of a sheep's milk beverage and a cow's milk beverage on recovery from strenuous eccentric exercise. Additionally, the effects of each beverage on satiety and gastrointestinal comfort were assessed.

Methods

Ten healthy males completed baseline measures of perceived muscle soreness and maximal voluntary concentric, eccentric, and isometric quadriceps force of one leg before completing 200 maximal eccentric knee extensions on an isokinetic dynamometer. Measures were repeated 0.5, 24, 48 and 72 h post-eccentric exercise. After 0.5 h measures, participants consumed either 450 ml of chocolate flavored sheep's milk or chocolate flavored cow's milk. Following a washout period, participants completed a second trial on the contralateral leg and consumed the other beverage. Additionally, a satiety and gastrointestinal comfort questionnaire was completed before and after each beverage was consumed.

Results

Eccentric exercise brought about a significant decrease in muscle function over time (all P < 0.012). No difference between treatments (all P > 0.097) was found. Measures of muscle soreness increased over time (all P < 0.002), however no difference was observed between treatments (all P > 0.072). Only sheep's milk altered perceived satiety, however, only the response to "How full do you feel" differed between treatments (P = 0.04).

Discussion

The results of this study suggest that consuming sheep's milk may provide similar benefits as cow's milk when recovering from exercise-induced muscle damage. While these findings provide initial support for the use of sheep's milk in a muscle recovery context, further research is warranted to confirm these findings. Given its superior nutritional profile, greater impact on satiety and lower environment impact, sheep's milk may be a more efficient post-exercise recovery beverage, compared to cow's milk.

Effect of blood flow restriction with low-load exercise on muscle damage in healthy adults: A systematic review of randomized controlled trials

INTRODUCTION

Blood flow restriction (BFR) is a relatively new rehabilitative technique and low-load exercise combined with BFR (LL-BFR) can increase muscle strength and muscle mass. However, it is currently unknown whether LL-BFR causes muscle damage. Therefore, the aim of this study is to investigate the effects of LL-BFR on muscle damage and provide recommendations for sports training and physical exercise.

MATERIALS AND METHODS

A systematic search was conducted using PubMed, Web of Science, Medline, Cochrane Library and Physiotherapy Evidence Database (PEDro) with a cut-off of March 2022. Randomized controlled trials (RCTs) and English-language studies were selected. Two independent assessors used the PEDro scoring scale to evaluate the methodological quality and risk of bias of the included studies.

RESULTS

Of the 2935 articles identified, 15 RCTs were included in this systematic review. Two studies demonstrated that LL-BFR could induce muscle damage in healthy individuals; however, two studies presented contrasting findings in the short term. Four studies found that no muscle damage occurred after LL-BFR in the long term. The remaining seven articles showed that it was unclear if LL-BFR could cause muscle damage, regardless of whether these participants were trained or not.

CONCLUSION

Although LL-BFR may induce muscle damage within 1 week, it will help gain long-term muscle strength and muscle hypertrophy. However, the lack of sufficient evidence on the effect of LL-BFR on muscle damage in clinical practice warrants additional RCTs with large sample sizes in the future.

Association between Gray-Scale Ultrasound Imaging and Serological Creatine Kinase for Quantifying Exercise-Induced Muscle Damage: An Observational Study

Limited evidence has verified if ultrasound imaging (US) can detect post-exercise muscle damage based on size, shape, and brightness metrics. This study aimed to analyze the correlation between creatine kinase (CK) concentration and (as a biomarker of muscle damage) changes in US gray-scale metrics after an exercise-induced muscle damage protocol. An observational study was conducted at a private university lab located in Madrid. Twenty-five untrained and asymptomatic volunteers were enrolled in this study. Baseline demographic data and body composition metrics were collected. In addition, the rectus femoris US data and CK concentration were assessed at baseline and after inducing muscle damage (24 and 48 h later). After calculating time differences for all the outcomes, the correlation between the changes observed with US and biomarkers was assessed. Significant CK concentration increases were found 24 h (p = 0.003) and 48 h (p < 0.001) after exercise. However, no significant changes in muscle size, shape, or brightness were found in any location (p > 0.05 for all). In addition, no significant associations were found between CK changes and US changes (p > 0.05 for all). Gray-scale US is not a sensitive tool for detecting muscle damage, as a protocol of exercise-induced muscle damage confirmed with CK produced no significant gray-scale US changes after 24 or 48 h. In addition, US and CK changes after 24 and 48 h were not associated with each other.

Acute Effect of the "Zero Point" Method on Muscle Thickness and Muscle Damage in Trained Men

The "zero point" method allows for lower intensities for an exercise session without impairing the total training volume. This study aimed to compare the effects of the "zero point" versus the traditional method on muscle responses and muscle damage in trained men. Fifteen experienced men (age: 27.7 ± 6.4 years; body mass: 78.4 ± 11.4 kg; height: 174.8 ± 4.9 cm; experience: 5.86 ± 4.7 years; relative bench press strength: 1.38 ± 0.17 kg·kg-1) were subjected to two exercise protocols in a randomized order and separated by a week. The traditional and "zero point" methods were applied in the bench press, with loads of 70% and 50% of one repetition maximum (1RM), respectively, for 10 sets until concentric failure, with 3-min intervals between sets. The zero point method displayed a higher number of repetitions and time under tension than the traditional method, with no difference in the total training volume, echo intensity, algometry, lactate, and myoglobin. For the muscle thickness, no differences between the groups were presented, except for the deltoid muscle thickness, in which a higher post-training volume was observed compared to traditional training. The "zero point" method increases the demand on the deltoid muscles in the bench press exercise, but not on the pectoralis and triceps brachii.

Effects of pre-sleep protein supplementation on plasma markers of muscle damage and inflammatory cytokines resulting from sprint interval training in trained swimmers

BACKGROUND

Pre-sleep protein has been shown to improve muscle recovery overnight following exercise-induced muscle damage. Whether such an approach affects recovery from sprint interval training (SIT) has yet to be elucidated. This study examined the effects of protein supplementation every night before sleep on early (45 min post-SIT) and late (24 and 48 h after SIT) responses of creatine kinase (CK) and inflammatory cytokines, including interleukin-6 and 10 (IL-6 and IL-10) and tumor necrosis factor-alpha (TNFα).

METHODS

Twenty trained swimmers underwent a 2-week in-water swimming SIT (two sets of 12 × 50-m all-out swims, interspersed by 1:1 recovery between each sprint and 3 min of rest between sets) and were randomized to two intervention groups receiving either 0.5 g kg-1 day-1 protein beverage (PRO) or the same amount of carbohydrate (CHO) preceding going to bed every night. For initial and final training sessions, CK and cytokine responses were analyzed at different time points, including resting, immediately after completion, 45 min post-SIT, and 24 and 48 h after SIT.

RESULTS

CK concentrations elevated from resting point to 24 and 48 h post-SIT for both PRO and CHO groups (p < 0.05). In both training groups, the peak levels of IL-6 and 10 were observed 45 min post-SIT on both occasions. TNFα levels significantly elevated from rest to immediately after SIT (p < 0.001) and returned to values equivalent to the baseline afterward in both groups and on both occasions. In both groups, swimming SIT also switched the cytokine response 48 hours after exercise to an anti-inflammatory status by decreasing the ratio of IL-6 to IL-10 (p < 0.04) in the last training session.

CONCLUSIONS

Pre-sleep protein ingestion failed to ameliorate blood markers of muscle damage. The late anti-inflammatory profile of cytokines and exercise-induced muscle damage improved after two weeks of swimming SIT with either protein or carbohydrate ingestion before sleep.

Influence of specific collagen peptides and 12-week concurrent training on recovery-related biomechanical characteristics following exercise-induced muscle damage-A randomized controlled trial

Introduction

It has been shown that short-term ingestion of collagen peptides improves markers related to muscular recovery following exercise-induced muscle damage. The objective of the present study was to investigate whether and to what extent a longer-term specific collagen peptide (SCP) supplementation combined with a training intervention influences recovery markers following eccentric exercise-induced muscle damage.

Methods

Fifty-five predominantly sedentary male participants were assigned to consume either 15 g SCP or placebo (PLA) and engage in a concurrent training (CT) intervention (30 min each of resistance and endurance training, 3x/week) for 12 weeks. Before (T1) and after the intervention (T2), eccentric muscle damage was induced by 150 drop jumps. Measurements of maximum voluntary contraction (MVC), rate of force development (RFD), peak RFD, countermovement jump height (CMJ), and muscle soreness (MS) were determined pre-exercise, immediately after exercise, and 24 and 48 h post-exercise. In addition, body composition, including fat mass (FM), fat-free mass (FFM), body cell mass (BCM) and extracellular mass (ECM) were determined at rest both before and after the 12-week intervention period.

Results

Three-way mixed ANOVA showed significant interaction effects in favor of the SCP group. MVC (p = 0.02, ηp2 = 0.11), RFD (p < 0.01, ηp2 = 0.18), peak RFD (p < 0.01, ηp2 = 0.15), and CMJ height (p = 0.046, ηp2 = 0.06) recovered significantly faster in the SCP group. No effects were found for muscle soreness (p = 0.66) and body composition (FM: p = 0.41, FFM: p = 0.56, BCM: p = 0.79, ECM: p = 0.58).

Conclusion

In summary, the results show that combining specific collagen peptide supplementation (SCP) and concurrent training (CT) over a 12-week period significantly improved markers reflecting recovery, specifically in maximal, explosive, and reactive strength. It is hypothesized that prolonged intake of collagen peptides may support muscular adaptations by facilitating remodeling of the extracellular matrix. This, in turn, could enhance the generation of explosive force.

Clinical trial registration

ClinicalTrials.gov, identifier ID: NCT05220371.

Effects of muscle fatigue on exercise-induced hamstring muscle damage: a three-armed randomized controlled trial

PURPOSE

Hamstring injuries in soccer reportedly increase towards the end of the matches' halves as well as with increased match frequency in combination with short rest periods, possibly due to acute or residual fatigue. Therefore, this study aimed to investigate the effects of acute and residual muscle fatigue on exercise-induced hamstring muscle damage.

METHODS

A three-armed randomized-controlled trial, including 24 resistance-trained males, was performed allocating subjects to either a training group with acute muscle fatigue + eccentric exercise (AF/ECC); residual muscle fatigue + eccentric exercise (RF/ECC) or a control group with only eccentric exercise (ECC). Muscle stiffness, thickness, contractility, peak torque, range of motion, pain perception, and creatine kinase were assessed as muscle damage markers pre, post, 1 h post, and on the consecutive three days.

RESULTS

Significant group × time interactions were revealed for muscle thickness (p = 0.02) and muscle contractility parameters radial displacement (Dm) and contraction velocity (Vc) (both p = 0.01), with larger changes in the ECC group (partial η2 = 0.4). Peak torque dropped by an average of 22% in all groups; stiffness only changed in the RF/ECC group (p = 0.04). Muscle work during the damage protocol was lower for AF/ECC than for ECC and RF/ECC (p = 0.005).

CONCLUSION

Hamstring muscle damage was comparable between the three groups. However, the AF/ECC group resulted in the same amount of muscle damage while accumulating significantly less muscle work during the protocol of the damage exercise.

TRIAL REGISTRATION

This study was preregistered in the international trial registration platform (WHO; registration number: DRKS00025243).

Prescribing statin therapy in physically (in)active individuals vs prescribing physical activity in statin-treated patients: A four-scenario practical approach

Statins are among the most commonly prescribed medications worldwide. Statin-associated muscle symptoms (SAMS) represent a frequent statin-related adverse effect associated with statin discontinuation and increased cardiovascular disease (CVD) events. Emerging evidence indicate that the majority of SAMS might not be actually caused by statins, and the nocebo/drucebo effect (i.e. adverse effects caused by negative expectations) might also explain SAMS. Physical activity (PA) is a cornerstone in the management of CVD risk. However, evidence of increased creatine-kinase levels in statin-treated athletes exposed to a marathon has been generalized, at least to some extent, to the general population and other types of PA. This generalization is likely inappropriate and might induce fear around PA in statin users. In addition, the guidelines for lipid management focus on aerobic PA while the potential of reducing sedentary behavior and undertaking resistance training have been overlooked. The aim of this report is to provide a novel proposal for the concurrent prescription of statin therapy and PA addressing the most common and clinically relevant scenarios by simultaneously considering the different stages of statin therapy and the history of PA. These scenarios include i) statin therapy initiation in physically inactive patients, ii) PA/exercise initiation in statin-treated patients, iii) statin therapy initiation in physically active patients, and iv) statin therapy in athletes and very active individuals performing SAMS-risky activities.

Probing muscle recovery following downhill running using precise mapping of MRI T2 relaxation times

PURPOSE

Postexercise recovery rate is a vital component of designing personalized training protocols and rehabilitation plans. Tracking exercise-induced muscle damage and recovery requires sensitive tools that can probe the muscles' state and composition noninvasively.

METHODS

Twenty-four physically active males completed a running protocol consisting of a 60-min downhill run on a treadmill at -10% incline and 65% of maximal heart rate. Quantitative mapping of MRI T2 was performed using the echo-modulation-curve algorithm before exercise, and at two time points: 1 h and 48 h after exercise.

RESULTS

T2 values increased by 2%-4% following exercise in the primary mover muscles and exhibited further elevation of 1% after 48 h. For the antagonist muscles, T2 values increased only at the 48-h time point (2%-3%). Statistically significant decrease in the SD of T2 values was found following exercise for all tested muscles after 1 h (16%-21%), indicating a short-term decrease in the heterogeneity of the muscle tissue.

CONCLUSION

MRI T2 relaxation time constitutes a useful quantitative marker for microstructural muscle damage, enabling region-specific identification for short-term and long-term systemic processes, and sensitive assessment of muscle recovery following exercise-induced muscle damage. The variability in T2 changes across different muscle groups can be attributed to their different role during downhill running, with immediate T2 elevation occurring in primary movers, followed by delayed elevation in both primary and antagonist muscle groups, presumably due to secondary damage caused by systemic processes.

Acute Recovery after a Fatigue Protocol Using a Recovery Sports Legging: An Experimental Study

Enhancing recovery is a fundamental component of high-performance sports training since it enables practitioners to potentiate physical performance and minimise the risk of injuries. Using a new sports legging embedded with an intelligent system for electrostimulation, localised heating and compression (completely embodied into the textile structures), we aimed to analyse acute recovery following a fatigue protocol. Surface electromyography- and torque-related variables were recorded on eight recreational athletes. A fatigue protocol conducted in an isokinetic dynamometer allowed us to examine isometric torque and consequent post-exercise acute recovery after using the sports legging. Regarding peak torque, no differences were found between post-fatigue and post-recovery assessments in any variable; however, pre-fatigue registered a 16% greater peak torque when compared with post-fatigue for localised heating and compression recovery methods. Our data are supported by recent meta-analyses indicating that individual recovery methods, such as localised heating, electrostimulation and compression, are not effective to recover from a fatiguing exercise. In fact, none of the recovery methods available through the sports legging tested was effective in acutely recovering the torque values produced isometrically.

2023 International Olympic Committee's (IOC) consensus statement on Relative Energy Deficiency in Sport (REDs)

Relative Energy Deficiency in Sport (REDs) was first introduced in 2014 by the International Olympic Committee's expert writing panel, identifying a syndrome of deleterious health and performance outcomes experienced by female and male athletes exposed to low energy availability (LEA; inadequate energy intake in relation to exercise energy expenditure). Since the 2018 REDs consensus, there have been >170 original research publications advancing the field of REDs science, including emerging data demonstrating the growing role of low carbohydrate availability, further evidence of the interplay between mental health and REDs and more data elucidating the impact of LEA in males. Our knowledge of REDs signs and symptoms has resulted in updated Health and Performance Conceptual Models and the development of a novel Physiological Model. This Physiological Model is designed to demonstrate the complexity of either problematic or adaptable LEA exposure, coupled with individual moderating factors, leading to changes in health and performance outcomes. Guidelines for safe and effective body composition assessment to help prevent REDs are also outlined. A new REDs Clinical Assessment Tool-Version 2 is introduced to facilitate the detection and clinical diagnosis of REDs based on accumulated severity and risk stratification, with associated training and competition recommendations. Prevention and treatment principles of REDs are presented to encourage best practices for sports organisations and clinicians. Finally, methodological best practices for REDs research are outlined to stimulate future high-quality research to address important knowledge gaps.

Twenty-Four Percent of Wildland Firefighters Reach Critical Levels of Serum Creatine Kinase During 80-Hour Critical Training

INTRODUCTION

Wildland firefighters (WLFFs) must undergo a 2-wk critical training (CT) period prior to deployment to the field. This stress may result in clinical risks, including severe muscle damage and rhabdomyolysis. We aimed to document the effects of WLFFs' CT on physiologic markers of muscle damage and soreness.

METHODS

Two interagency hotshot crews (n=25) were followed during spring 2022 for 80 h of training. Activity counts as well as records of upper-body (US) and lower-body (LS) muscle soreness were collected daily. Body weight (BW) and skinfold measurements were recorded on Day 1 (D1) and D11 to estimate body fat (BF) and lean body weight (LBW). Blood was collected on D1 and D11 to measure muscle and liver damage markers.

RESULTS

Critical training resulted in significant elevations in creatine kinase (CK) (216.9±57.4 U/L vs 5166.4±1927.8 U/L, P=0.017) and lactate dehydrogenase (LDH) (175.5±4.0 IU/L vs 340.0±42.6 IU/L, P=0.001) despite no significant changes in BW, BF, LBW, cortisol, or testosterone. Main effects of time were seen in US and LS, peaking on D11 (US: 5.2±0.4 cm, P<0.001; LS: 5.5±0.4 cm, P<0.001). Those who spent the most minutes with activity counts of >1500 counts/min showed the greatest increase in CK and LDH.

CONCLUSIONS

These data suggest that WLFFs undergo significant physiologic stressors, resulting in muscle soreness and damage during CT, with 6 of the 25 subjects reaching critical levels of serum CK. It appears that much of the muscle damage and soreness occurred because of unaccustomed WLFF job-specific tasks.

Methodology for studying Relative Energy Deficiency in Sport (REDs): a narrative review by a subgroup of the International Olympic Committee (IOC) consensus on REDs

In the past decade, the study of relationships among nutrition, exercise and the effects on health and athletic performance, has substantially increased. The 2014 introduction of Relative Energy Deficiency in Sport (REDs) prompted sports scientists and clinicians to investigate these relationships in more populations and with more outcomes than had been previously pursued in mostly white, adolescent or young adult, female athletes. Much of the existing physiology and concepts, however, are either based on or extrapolated from limited studies, and the comparison of studies is hindered by the lack of standardised protocols. In this review, we have evaluated and outlined current best practice methodologies to study REDs in an attempt to guide future research.This includes an agreement on the definition of key terms, a summary of study designs with appropriate applications, descriptions of best practices for blood collection and assessment and a description of methods used to assess specific REDs sequelae, stratified as either Preferred, Used and Recommended or Potential Researchers can use the compiled information herein when planning studies to more consistently select the proper tools to investigate their domain of interest. Thus, the goal of this review is to standardise REDs research methods to strengthen future studies and improve REDs prevention, diagnosis and care.

The Effect of Extremely Low-Frequency Electromagnetic Fields on Inflammation and Performance-Related Indices in Trained Athletes: A Double-Blinded Crossover Study

Previous investigations have demonstrated the therapeutic advantages of extremely low-frequency electromagnetic fields (ELF-EMFs) in mitigating inflammation and influencing biological processes. We aimed to shed light on the effects of ELF-EMF on recovery rate following high-intensity exercise. Nine male athletes (26.7 ± 6.0 years; 69.6 ± 7.7 kg, VO2peak 57.3 ± 6.8 mL/kg/min) completed five visits in a double-blinded crossover design, performing two consecutive testing days, following a ventilatory thresholds assessment. Following 62 min of high-intensity cycling, participants lay on an ELF-EMF mattress under active (A) and non-active (NA) conditions, immediately post protocol and during the night. Physical performance and blood markers were assessed at baseline and at 60 min (60 P) and 24 h (24 H) post-protocol. The A-condition demonstrated a notable reduction in interleukin-10 (IL-10) concentrations (mean difference = -88%, p = 0.032) and maximal isometric strength of the quadriceps muscles (mean difference = ~8%, p = 0.045) compared to the NA-condition between 60 P and 24 H. In a sensitivity analysis, the A-condition revealed that younger athletes who possessed lower fat mass experienced attenuated inflammation and biochemical responses and improved physical performance. In conclusion, ELF-EMF showed no significant overall effects on performance and inflammation after intense cycling among athletes. Post-hoc analysis revealed modest benefits of ELF-MLF, suggesting a context-dependent impact. Further research with a larger sample size and multiple sessions is needed to confirm the recovery potential of ELF-EMF.

The molecular athlete: exercise physiology from mechanisms to medals

Human skeletal muscle demonstrates remarkable plasticity, adapting to numerous external stimuli including the habitual level of contractile loading. Accordingly, muscle function and exercise capacity encompass a broad spectrum, from inactive individuals with low levels of endurance and strength to elite athletes who produce prodigious performances underpinned by pleiotropic training-induced muscular adaptations. Our current understanding of the signal integration, interpretation, and output coordination of the cellular and molecular mechanisms that govern muscle plasticity across this continuum is incomplete. As such, training methods and their application to elite athletes largely rely on a "trial-and-error" approach, with the experience and practices of successful coaches and athletes often providing the bases for "post hoc" scientific enquiry and research. This review provides a synopsis of the morphological and functional changes along with the molecular mechanisms underlying exercise adaptation to endurance- and resistance-based training. These traits are placed in the context of innate genetic and interindividual differences in exercise capacity and performance, with special consideration given to aging athletes. Collectively, we provide a comprehensive overview of skeletal muscle plasticity in response to different modes of exercise and how such adaptations translate from "molecules to medals."

Oxidative Stress and Skeletal Muscle Function

Skeletal muscle is continuously exposed during its activities to mechanical/oxidative damage [...].