Exercise-Induced Muscle Damage and Recovery in Young and Middle-Aged Males with Different Resistance Training Experience

Age-associated functional healing of musculoskeletal trauma through regenerative engineering and rehabilitation

Traumatic musculoskeletal injuries that lead to volumetric muscle loss (VML) are challenged by irreparable soft tissue damage, impaired regenerative ability, and reduced muscle function. Regenerative rehabilitation strategies involving the pairing of engineered therapeutics with exercise have guided considerable advances in the functional repair of skeletal muscle following VML. However, few studies evaluate the efficacy of regenerative rehabilitation across the lifespan. In the current study, young and aged mice are treated with an engineered muscle, consisting of nanofibrillar-aligned collagen laden with myogenic cells, in combination with voluntary running activity following a VML injury. Overall, young mice perform at higher running volumes and intensities compared to aged mice but exhibit similar volumes relative to age-matched baselines. Additionally, young mice are highly responsive to the dual treatment showing enhanced force production (p < 0.001), muscle mass (p < 0.05), and vascular density (p < 0.01) compared to age-matched controls. Aged mice display upregulation of circulating inflammatory cytokines and show no significant regenerative response to treatment, suggesting a diminished efficacy of regenerative rehabilitation in aged populations. These findings highlight the restorative potential of regenerative engineering and rehabilitation for the treatment of traumatic musculoskeletal injuries in young populations and the complimentary need for age-specific interventions and studies to serve broader patient demographics.

Youths Are Less Susceptible to Exercise-Induced Muscle Damage Than Adults: A Systematic Review With Meta-Analysis

PURPOSE

This meta-analysis aimed to (1) provide a comparison of peak changes in indirect markers of exercise-induced muscle damage (EIMD) in youths versus adults and (2) determine if the involved limb moderated this effect.

METHOD

Studies were eligible for inclusion if they (1) provided a human youth versus adult comparison; (2) provided data on muscle strength, soreness, or creatine kinase markers beyond ≥24 hours; and (3) did not provide a recovery treatment. Effect sizes (ES) were presented alongside 95% confidence intervals.

RESULTS

EIMD exhibited larger effects on adults than in youths for muscle strength (ES = -2.01; P < .001), muscle soreness (ES = -1.52; P < .001), and creatine kinase (ES = -1.98; P < .001). The random effects meta-regression indicated that the effects of upper- and lower-limb exercise in youths and adults were significant for muscle soreness (coefficient estimate = 1.11; P < .001) but not for muscle strength or creatine kinase (P > .05). As such, the between-group effects for muscle soreness (ES = -2.10 vs -1.03; P < .05) were greater in the upper than lower limbs.

CONCLUSION

The magnitude of EIMD in youths is substantially less than in their adult counterparts, and this effect is greater in upper than lower limbs for muscle soreness. These findings help guide practitioners who may be concerned about the potential impact of EIMD when training youth athletes.

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.

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.

Grass-Fed and Non-Grass-Fed Whey Protein Consumption Do Not Attenuate Exercise-Induced Muscle Damage and Soreness in Resistance-Trained Individuals: A Randomized, Placebo-Controlled Trial

Eccentric muscle contractions can cause structural damage to muscle cells resulting in temporarily decreased muscle force production and soreness. Prior work indicates pasture-raised dairy products from grass-fed cows have greater anti-inflammatory and antioxidant properties compared to grain-fed counterparts. However, limited research has evaluated the utility of whey protein from pasture-raised, grass-fed cows to enhance recovery compared to whey protein from non-grass-fed cows. Therefore, using a randomized, placebo-controlled design, we compared the effect of whey protein from pasture-raised, grass-fed cows (PRWP) to conventional whey protein (CWP) supplementation on indirect markers of muscle damage in response to eccentric exercise-induced muscle damage (EIMD) in resistance-trained individuals. Thirty-nine subjects (PRWP, n = 14; CWP, n = 12) completed an eccentric squat protocol to induce EIMD with measurements performed at 24, 48, and 72 h of recovery. Dependent variables included: delayed onset muscle soreness (DOMS), urinary titin, maximal isometric voluntary contraction (MIVC), potentiated quadriceps twitch force, countermovement jump (CMJ), and barbell back squat velocity (BBSV). Between-condition comparisons did not reveal any significant differences (p ≤ 0.05) in markers of EIMD via DOMS, urinary titin, MIVC, potentiated quadriceps twitch force, CMJ, or BBSV. In conclusion, neither PRWP nor CWP attenuate indirect markers of muscle damage and soreness following eccentric exercise in resistance-trained individuals.

Recovery from Resistance Exercise in Older Adults: A Systematic Scoping Review

BACKGROUND

Resistance exercise is recommended for maintaining muscle mass and strength in older adults. However, little is known about exercise-induced muscle damage and recovery from resistance exercise in older adults. This may have implications for exercise prescription. This scoping review aimed to identify and provide a broad overview of the available literature, examine how this research has been conducted, and identify current knowledge gaps relating to exercise-induced muscle damage and recovery from resistance exercise in older adults.

METHODS

Studies were included if they included older adults aged 65 years and over, and reported any markers of exercise-induced muscle damage after performing a bout of resistance exercise. The following electronic databases were searched using a combination of MeSH terms and free text: MEDLINE, Scopus, Embase, SPORTDiscus and Web of Science. Additionally, reference lists of identified articles were screened for eligible studies. Data were extracted from eligible studies using a standardised form. Studies were collated and are reported by emergent theme or outcomes.

RESULTS

A total of 10,976 possible articles were identified and 27 original research articles were included. Findings are reported by theme; sex differences in recovery from resistance exercise, symptoms of exercise-induced muscle damage, and biological markers of muscle damage.

CONCLUSIONS

Despite the volume of available data, there is considerable variability in study protocols and inconsistency in findings reported. Across all measures of exercise-induced muscle damage, data in women are lacking when compared to males, and rectifying this discrepancy should be a focus of future studies. Current available data make it challenging to provide clear recommendations to those prescribing resistance exercise for older people.

Can infrared thermography serve as an alternative to assess cumulative fatigue in women?

Muscle fatigue can limit performance both in sports and daily life activities. Consecutive days of exercise without a proper recovery time may elicit cumulative fatigue. Although it has been speculated that skin temperature could serve as an indirect indicator of exercise-induced adaptations, it is unclear if skin temperature measured by infrared thermography (IRT) could be an outcome related to the effects of cumulative fatigue. In this study, we recruited 21 untrained women and induced cumulative fatigue in biceps brachii over two consecutive days of exercise. We measured delayed onset muscle soreness (DOMS, using a numeric rate scale), maximal strength (using a dynamometer), and skin temperature (using IRT) in exercise and non-exercise muscles. Cumulative fatigue reduced muscle strength and increased DOMS. Skin temperature in the arm submitted to cumulative fatigue was higher for minimum and mean temperature, being asymmetrical in relation to the control arm. We also observed that the variations in the minimum and mean temperatures correlated with the strength losses. In summary, skin temperature measured by IRT seems promising to help detect cumulative fatigue in untrained women, being useful to explain strength losses. Future studies should provide additional evidence for the potential applications not only in trained participants but also in patients that may not be able to report outcomes of scales or precisely report DOMS.

Exercise induced muscle damage and repeated bout effect: an update for last 10 years and future perspectives

Exercise-induced muscle damage (EIMD) and repeated bout effect (RBE) are widely researched across various populations. EIMD is the muscle damage occurring after one bout of unaccustomed exercise while RBE is the attenuation of the same muscle damage in subsequent second bout. RBE seems to have significant implications for exercise prescription. Despite existence of vast literature, there is lack of clarity on the effects of EIMD and RBE in a healthy population. The purpose of this study is to review the literature on EIMD and RBE in healthy participants published during the last 10 years. The search of major databases (including Scopus, Google Scholar and PubMed) was conducted using specific keywords ‘Exercise induced muscle damage’, ‘Repeated bout effect’, ‘Healthy participants’ ‘Pre-conditioning’, ‘Eccentric exercise’. Studies published from 2011 onwards which included EIMD and RBE assessment in healthy participants were included in this review. Database searching revealed a total of 38 studies on EIMD and RBE in healthy participants. Three major themes of papers were identified that focused on EIMD and RBE along with (1) age related differences, (2) sex-based differences, and (3) response in athletes. Findings of this comprehensive review suggests that both EIMD and RBE are age, and sex specific. Delayed onset muscle soreness played a major role in both EIMD and RBE in all the population types. Female participants are less susceptible to EIMD as compared to age-matched male counterparts. Moreover, both EIMD and RBE are more elicited in middle aged and younger adults as compared to children and older adults while the magnitude of RBE turns out to be minimal in trained individuals due to persisting adaptations.

Age Differences in Recovery Rate Following an Aerobic-Based Exercise Protocol Inducing Muscle Damage Among Amateur, Male Athletes

Purpose: Compare recovery rates between active young (Y) and middle-aged (MA) males up to 48H post aerobically based, exercise-induced muscle damage (EIMD) protocol. A secondary aim was to explore the relationships between changes in indices associated with EIMD and recovery throughout this timeframe.

Methods: Twenty-eight Y (n = 14, 26.1 ± 2.9y, 74.5 ± 9.3 kg) and MA (n = 14, 43.6 ± 4.1y, 77.3 ± 12.9 kg) physically active males, completed a 60-min downhill running (DHR) on a treadmill at −10% incline and at 65% of maximal heart rate (HR). Biochemical, biomechanical, psychological, force production and muscle integrity (using MRI diffusion tensor imaging) markers were measured at baseline, immediately-post, and up to 48H post DHR.

Results: During the DHR, HR was lower (p < 0.05) in MA compared to Y, but running pace and distance covered were comparable between groups. No statistical or meaningful differences were observed between groups for any of the outcomes. Yet, Significant (p < 0.05) time-effects within each group were observed: markers of muscle damage, cadence and perception of pain increased, while TNF-a, isometric and dynamic force production and stride-length decreased. Creatine-kinase at 24H-post and 48H-post were correlated (p < 0.05, r range = −0.57 to 0.55) with pain perception, stride-length, and cadence at 24H-post and 48H-post. Significant (p < 0.05) correlations were observed between isometric force production at all time-points and IL-6 at 48H-post DHR (r range = −0.62 to (−0.74).

Conclusion: Y and MA active male amateur athletes recover in a comparable manner following an EIMD downhill protocol. These results indicate that similar recovery strategies can be used by trainees from both age groups following an aerobic-based EIMD protocol.

Beneficial Effects of Flavonoids on Skeletal Muscle Health: A Systematic Review and Meta-Analysis

Skeletal muscle (SkM) is a highly dynamic tissue that responds to physiological adaptations or pathological conditions, and SkM mitochondria play a major role in bioenergetics, regulation of intracellular calcium homeostasis, pro-oxidant/antioxidant balance, and apoptosis. Flavonoids are polyphenolic compounds with the ability to modulate molecular pathways implicated in the development of mitochondrial myopathy. Therefore, it is pertinent to explore its potential application in conditions such as aging, disuse, denervation, diabetes, obesity, and cancer. To evaluate preclinical and clinical effects of flavonoids on SkM structure and function. We performed a systematic review of published studies, with no date restrictions applied, using PubMed and Scopus. The following search terms were used: "flavonoids" OR "flavanols" OR "flavones" OR "anthocyanidins" OR "flavanones" OR "flavan-3-ols" OR "catechins" OR "epicatechin" OR "(-)-epicatechin" AND "skeletal muscle." The studies included in this review were preclinical studies, clinical trials, controlled clinical trials, and randomized-controlled trials that investigated the influence of flavonoids on SkM health. Three authors, independently, assessed trials for the review. Any disagreement was resolved by consensus. The use of flavonoids could be a potential tool for the prevention of muscle loss. Their effects on metabolism and on mitochondria function suggest their use as muscle regulators.

Recovery from resistance exercise in older adults: a protocol for a scoping review

Introduction

Resistance exercise has been shown to improve muscle health in older adults and is recommended as a front-line treatment for many health conditions, including sarcopenia and frailty. However, despite considerable research detailing the potential benefits of resistance exercise programmes, little is known about how older adults recover from individual exercise sessions. This scoping review will examine the current evidence surrounding the acute post-exercise effects of resistance exercise and the exercise recovery process in older adults to inform future research and exercise prescription guidelines for older adults.

Methods and analysis

The methodological framework of Arksey and O’Malley (2005) will be applied for this scoping review. A systematic search of five online databases and the hand-searching of reference lists of identified articles will be used to identify relevant papers. Studies that aim to measure exercise-induced muscle damage or exercise recovery following a resistance exercise session in participants aged 65 years and over will be included. Qualitative and quantitative data from relevant studies will be presented in a tabular format. Results will be summarised in narrative format. Key findings will be discussed concerning resistance exercise prescription in older adults.

Dissemination

This review will be used to direct further research surrounding the exercise recovery process from resistance exercise in older adults and will also aid in designing specific exercise prescription guidelines for an older population. Findings will be relevant to researchers, clinicians, health workers and policy-makers and disseminated through publications and presentations.

Preliminary Investigations Into the Effect of Exercise-Induced Muscle Damage on Systemic Extracellular Vesicle Release in Trained Younger and Older Men

Background: Exercise-induced muscle damage (EIMD) results in transient muscle inflammation, strength loss, and muscle soreness and may cause subsequent exercise avoidance. Research has recently proven that skeletal muscle can also release extracellular vesicles (EVs) into the circulation following a bout of exercise. However, EV’s potential role, including as a biomarker, in the response to eccentric resistance exercise stimulus remains unclear.

Methods: Twelve (younger, n=7, 27.0±1.5years and older, n=5, 63.0±1.0years) healthy, physically active males, undertaking moderate, regular physical activity (3–5 times per week) performed a unilateral high intensity eccentric exercise protocol. Venous plasma was collected for assessment of EVs and creatine kinase (CK) prior to EIMD, immediately after EIMD, and 1–72h post-EIMD, and maximal voluntary isometric contraction (MVIC) and delayed onset muscle soreness (DOMS) were assessed at all time points, except 1 and 2h post-EIMD.

Results: A significant effect of both time (p=0.005) and group (p<0.001) was noted for MVIC, with younger participants’ MVIC being higher throughout. Whilst a significant increase was observed in DOMS in the younger group (p=0.014) and in the older group (p=0.034) following EIMD, no significant differences were observed between groups. CK was not different between age groups but was altered following the EIMD (main effect of time p=0.026), with increased CK seen immediately post-, at 1 and 2h post-EIMD. EV count tended to be lower in older participants at rest, relative to younger participants (p=0.056), whilst EV modal size did not differ between younger and older participants pre-EIMD. EIMD did not substantially alter EV modal size or EV count in younger or older participants; however, the alteration in EV concentration (ΔCount) and EV modal size (ΔMode) between post-EIMD and pre-EIMD negatively associated with CK activity. No significant associations were noted between MVIC or DOMS and either ΔCount or ΔMode of EVs at any time point.

Conclusion: These findings suggest that profile of EV release, immediately following exercise, may predict later CK release and play a role in the EIMD response. Exercise-induced EV release profiles may therefore serve as an indicator for subsequent muscle damage.

Sprint mechanical properties of professional rugby league players according to playing standard, age and position, and the association with key physical characteristics

BACKGROUND

This study determined the influence of playing standard, age, and position on the horizontal force-velocity (FV) properties of rugby league players, and the association with other characteristics.

METHODS

This observational study used a cross-sectional design with a range of physical characteristics recorded from 132 players from 5 Super League clubs. Sprint data was used to derived theoretical maximal force (F0) and velocity (V0), power (Pmax), maximal rate of force (RFmax) and the rate of decrease in RFmax (DRF). Differences between playing standard, age groups and playing positions were determined (P value and standardised mean difference (SMD) along with correlational analysis to assess the relationship between FV properties and key physical characteristics.

RESULTS

Senior players reported lower split time (SMD = -0.26--0.59, P =0.002-0.017), absolute F0, Pmax and V0 (SMD = 0.47-0.78, P <0.001-0.010). Players aged <21 years reported higher split times and lower absolute F0 compared to 21-26 years (SMD = -0.84--0.56, P <0.001-0.04) and a lower V0 than >26 years (SMD = -0.40, P=0.002). Hit-up forwards were slower than outside backs (SMD = -0.30--0.89, P <0.001-0.042), though produced the highest absolute F0 and Pmax. Split times F0, V0, Pmax and RFmax were associated with change of direction and countermovement jump performance, whilst FVslope and DRF were associated with countermovement jump performance. F0 and Pmax were associated with medicine ball throw distance (r = 0.302-0371, P = ≤0.001). There was no association with prone Yo-Yo IR1 distance (r = -0.16-0.09, P =0.060-0.615).

CONCLUSIONS

These results provide insight into the horizontal FV properties with reference to key sub-groups, and highlights several associations with other characteristics across large sample of rugby league players. The result of this study should be used when interpreting the sprint ability of rugby league players, planning the long-term development of youth players, and inform programme design for all.

The influence of age on the recovery from worksite resistance exercise in career firefighters

Resistance exercise is an important strategy to reduce injuries and improve performance in the fire service. However, given the large age range of firefighters, it is important to determine if age influences their recovery following an acute bout of resistance exercise.

PURPOSE

To examine the changes in indirect markers of muscle damage in young and older firefighters following a feasible worksite resistance exercise routine.

METHODS

Nineteen young (25.5 ± 3.4 years) and 19 older male career firefighters (50.3 ± 3.5 years) completed pre-testing, an acute bout of resistance exercise, and post-testing at 24, 48, and 72 h post-exercise at their fire station. Prior to all testing, firefighters completed a work-related fatigue (WRF) questionnaire to account for potential unanticipated differences in previous shift workloads. Testing included perceived muscle soreness, ultrasonography to quantify muscle size and echo intensity (EI) of the vastus lateralis (VL) and biceps brachii (BB), countermovement jump (CMJ) height and velocity, upper body (UB) peak force (PF), lower body (LB) PF and rapid force, and electromyographic (EMG) amplitude of the VL. The resistance training session included 3 sets of 8-10 repetitions of a deadlift, shoulder press, lunge, and upright row exercise at 80% 1-RM. All recovery variables were analyzed using a linear mixed model, controlling for WRF.

RESULTS

There was no interaction (age × time) for any of the variables and a similar training volume were completed between groups (P ≥ 0.171). Muscle soreness, CMJ height and velocity, UB PF, LB rapid force and EMG amplitude at later time intervals (100-200 ms), and VL and BB muscle size were altered from baseline (P ≤ 0.044) for 48, 24, 48, 72, and 72 h post-exercise, respectively. Young firefighters exhibited greater CMJ height and velocity, LB PF, LB rapid force (200 ms), and lower VL EI values than the older firefighters (P ≤ 0.047).

CONCLUSIONS

Age did not influence the recovery from an acute bout of worksite resistance exercise in firefighters. However, UB muscle strength, CMJ performance, and LB rapid force production were reduced 24-72 h post-exercise. Appropriately scheduled and chronic on-duty resistance training may mitigate these decrements.

Does Branched-Chain Amino Acids (BCAAs) Supplementation Attenuate Muscle Damage Markers and Soreness after Resistance Exercise in Trained Males? A Meta-Analysis of Randomized Controlled Trials

Previous studies have reported the positive effects of branched-chain amino acids (BCAAs) supplementation on lowering plasma markers of muscle damage and subjective soreness after resistance exercise. However, a variety of factors can potentially moderate its efficacy. This meta-analysis aimed to summarize the evidence regarding the effect of BCAAs supplementation on plasma muscle damage markers and soreness after resistance exercise in only trained males, by considering the plasma lactate dehydrogenase (LDH) and creatine kinase (CK). Randomized controlled trials were identified through a computerized literature search for the period 2010–2020. The pooled data were analyzed with the random-effects model and heterogeneity using I². Cochrane Collaboration tools was used for the assessment of risk of bias. Nine studies met the inclusion criteria. A positive effect was found for CK at <24, 24, and 48 h after exercise and for muscle soreness at <24 h only. However, the positive effect was not evident for plasma LDH at any follow-up time. Different outcomes for post-exercise responses may suggest that BCAAs supplementation can attenuate muscle damage and ameliorate muscle soreness after resistance exercise in trained males.

Prediction of One Repetition Maximum Using Reference Minimum Velocity Threshold Values in Young and Middle-Aged Resistance-Trained Males

Background: This study determined the accuracy of different velocity-based methods when predicting one-repetition maximum (1RM) in young and middle-aged resistance-trained males. Methods: Two days after maximal strength testing, 20 young (age 21.0 ± 1.6 years) and 20 middle-aged (age 42.6 ± 6.7 years) resistance-trained males completed three repetitions of bench press, back squat, and bent-over-row at loads corresponding to 20–80% 1RM. Using reference minimum velocity threshold (MVT) values, the 1RM was estimated from the load-velocity relationships through multiple (20, 30, 40, 50, 60, 70, and 80% 1RM), two-point (20 and 80% 1RM), high-load (60 and 80% 1RM) and low-load (20 and 40% 1RM) methods for each group. Results: Despite most prediction methods demonstrating acceptable correlations (r = 0.55 to 0.96), the absolute errors for young and middle-aged groups were generally moderate to high for bench press (absolute errors = 8.2 to 14.2% and 8.6 to 20.4%, respectively) and bent-over-row (absolute error = 14.9 to 19.9% and 8.6 to 18.2%, respectively). For squats, the absolute errors were lower in the young group (5.7 to 13.4%) than the middle-aged group (13.2 to 17.0%) but still unacceptable. Conclusion: These findings suggest that reference MVTs cannot accurately predict the 1RM in these populations. Therefore, practitioners need to directly assess 1RM.

Aging and Recovery After Resistance-Exercise-Induced Muscle Damage: Current Evidence and Implications for Future Research

Aging is anecdotally associated with a prolonged recovery from resistance training, though current literature remains equivocal. This brief review considers the effects of resistance training on indirect markers of muscle damage and recovery (i.e., muscle soreness, blood markers, and muscle strength) in older males. With no date restrictions, four databases were searched for articles relating to aging, muscle damage, and recovery. Data from 11 studies were extracted for review. Of these, four reported worse symptoms in older compared with younger populations, while two have observed the opposite, and the remaining studies (n = 6) proposed no differences between age groups. It appears that resistance training can be practiced in older populations without concern for impaired recovery. To improve current knowledge, researchers are urged to utilize more ecologically valid muscle-damaging bouts and investigate the mechanisms which underpin the recovery of muscle soreness and strength after exercise in older populations.

Ubiquitin Proteasome System Activity is Suppressed by Curcumin following Exercise-Induced Muscle Damage in Human Skeletal Muscle

PURPOSE

Curcumin is a polyphenolic compound that is suggested to dysregulate the ubiquitin-proteasome system (UPS). This study investigated the effects of curcumin supplementation on markers of UPS activity in response to muscle damage.

METHODS

Twenty-three recreationally active male and females between the ages of 18-30 were randomized into a curcumin (CUR) or placebo (PLA) group. Both groups ingested 2 g of their respective supplement and 20 mg of piperine for 11 consecutive days. Following 8 consecutive days of supplementation, participants performed a 45-minute eccentrically-biased treadmill protocol at 60% VO2max. Muscle biopsies and delayed onset muscle soreness (DOMS) assessments were performed 30 minutes prior and 3, 24, 48, and 72 hours following exercise. Skeletal muscle ubiquitin, MAFbx/Atrogin-1, ubiquitin specific peptidase 19 (USP19), and chymotrypsin-like protease concentrations were measured using ELISA. A 3-way repeated measures ANOVA with pairwise comparisons was conducted with significance set at p ≤ 0.05.

RESULTS

Compared to baseline, DOMS for both groups was significantly increased (p < 0.05) at all time points except 72 hours following exercise. No significant differences were found for USP19 between groups. Ubiquitin (p=.016) and MAFbx/Atrogin-1 (p=.006) were significantly lower for CUR compared to PLA. Additionally, MAFbx/Atrogin-1 was significantly greater for females (p=.013) compared to males. In males, curcumin resulted in significant reductions (p = .049) in chymotrypsin-like protease (p = .049).

CONCLUSION

While elevations in UPS activity were not observed in response to muscle damage, curcumin supplementation in humans does appear to dysregulate basal UPS activity in the presence of exercise-induced muscle damage.

Effects of Pre-Sleep Whey vs. Plant-Based Protein Consumption on Muscle Recovery Following Damaging Morning Exercise

Pre-sleep whey protein intake has been shown to improve overnight muscle protein synthesis, muscle size and strength, and muscle recovery. Despite a growing interest in alternative protein sources, such as plant-based protein, there is no evidence regarding the efficacy of plant-based proteins consumed pre-sleep. Therefore, we aimed to compare whey vs. plant-based pre-sleep protein dietary supplementation on muscle recovery in middle-aged men. Twenty-seven recreationally active, middle-aged men performed 5 sets of 15 repetitions of maximal eccentric voluntary contractions (ECC) for the knee extensors (ext) and flexors (flex), respectively, in the morning. Participants consumed 40 g of either whey hydrolysate (WH, n = 9), whey isolate (WI, n = 6), rice and pea combination (RP, n = 6), or placebo (PL, n = 6) 30 min pre-sleep on the day of ECC and the following two nights. Catered meals (15% PRO, 55% CHO, 30% Fat) were provided to participants for 5 days to standardize nutrition. Plasma creatine kinase (CK), interleukin-6 (IL-6), and interleukin-10 (IL-10) were measured at pre, immediately post (+0), +4, +6, +24, +48, and +72 h post-ECC. Isometric (ISOM) and isokinetic (ISOK) maximal voluntary contraction force were measured at pre, immediately post (+0), +24, +48, and +72 h post-ECC. Muscle soreness, thigh circumference, and HOMA-IR were measured at pre, +24, +48, and +72 h post-ECC. CK was increased at +4 h post-ECC, remained elevated at all time points compared to baseline (p < 0.001), and was significantly greater at +72 h compared to all other time points (p < 0.001). IL-6 was increased at +6 h (p = 0.002) with no other time differing from baseline. ISOMext was reduced after ECC (p = 0.001) and remained reduced until returning to baseline at +72 h. ISOMflex, ISOKext, and ISOKflex were reduced after ECC and remained reduced at +72 h (p < 0.001). Muscle soreness increased post-ECC (p < 0.001) and did not return to baseline. Thigh circumference (p = 0.456) and HOMA-IR (p = 0.396) did not change post-ECC. There were no significant differences between groups for any outcome measure. These data suggest that middle-aged men consuming 1.08 ± 0.02 g/kg/day PRO did not recover from damaging eccentric exercise at +72 h and that pre-sleep protein ingestion, regardless of protein source, did not aid in muscle recovery when damaging eccentric exercise was performed in the morning.