The prevention and treatment of exercise-induced muscle damage

Pathophysiology of exercise-induced muscle damage and its structural, functional, metabolic, and clinical consequences

Extreme or unaccustomed eccentric exercise can cause exercise-induced muscle damage, characterized by structural changes involving sarcomere, cytoskeletal, and membrane damage, with an increased permeability of sarcolemma for proteins. From a functional point of view, disrupted force transmission, altered calcium homeostasis, disruption of excitation-contraction coupling, as well as metabolic changes bring about loss of strength. Importantly, the trauma also invokes an inflammatory response and clinically presents itself by swelling, decreased range of motion, increased passive tension, soreness, and a transient decrease in insulin sensitivity. While being damaging and influencing heavily the ability to perform repeated bouts of exercise, changes produced by exercise-induced muscle damage seem to play a crucial role in myofibrillar adaptation. Additionally, eccentric exercise yields greater hypertrophy than isometric or concentric contractions and requires less in terms of metabolic energy and cardiovascular stress, making it especially suitable for the elderly and people with chronic diseases. This review focuses on our current knowledge of the mechanisms underlying exercise-induced muscle damage, their dependence on genetic background, as well as their consequences at the structural, functional, metabolic, and clinical level. A comprehensive understanding of these is a prerequisite for proper inclusion of eccentric training in health promotion, rehabilitation, and performance enhancement.

Nutritional interventions for reducing the signs and symptoms of exercise-induced muscle damage and accelerate recovery in athletes: current knowledge, practical application and future perspectives

PURPOSE

This review provides an overview of the current knowledge of the nutritional strategies to treat the signs and symptoms related to EIMD. These strategies have been organized into the following sections based upon the quality and quantity of the scientific support available: (1) interventions with a good level of evidence; (2) interventions with some evidence and require more research; and (3) potential nutritional interventions with little to-no-evidence to support efficacy.

METHOD

Pubmed, EMBASE, Scopus and Web of Science were used. The search terms 'EIMD' and 'exercise-induced muscle damage' were individually concatenated with 'supplementation', 'athletes', 'recovery', 'adaptation', 'nutritional strategies', hormesis'.

RESULT

Supplementation with tart cherries, beetroot, pomegranate, creatine monohydrate and vitamin D appear to provide a prophylactic effect in reducing EIMD. β-hydroxy β-methylbutyrate, and the ingestion of protein, BCAA and milk could represent promising strategies to manage EIMD. Other nutritional interventions were identified but offered limited effect in the treatment of EIMD; however, inconsistencies in the dose and frequency of interventions might account for the lack of consensus regarding their efficacy.

CONCLUSION

There are clearly varying levels of evidence and practitioners should be mindful to refer to this evidence-base when prescribing to clients and athletes. One concern is the potential for these interventions to interfere with the exercise-recovery-adaptation continuum. Whilst there is no evidence that these interventions will blunt adaptation, it seems pragmatic to use a periodised approach to administering these strategies until data are in place to provide and evidence base on any interference effect on adaptation.

The unaided recovery of marathon-induced serum metabolome alterations

Endurance athlete performance is greatly dependent on sufficient post-race system recovery, as endurance races have substantial physiological, immunological and metabolic effects on these athletes. To date, the effects of numerous recovery modalities have been investigated, however, very limited literature exists pertaining to metabolic recovery of athletes after endurance races without the utilisation of recovery modalities. As such, this investigation is aimed at identifying the metabolic recovery trend of athletes within 48 h after a marathon. Serum samples of 16 athletes collected 24 h before, immediately after, as well as 24 h and 48 h post-marathon were analysed using an untargeted two-dimensional gas chromatography time-of-flight mass spectrometry metabolomics approach. The metabolic profiles of these comparative time-points indicated a metabolic shift from the overall post-marathon perturbed state back to the pre-marathon metabolic state during the recovery period. Statistical analyses of the data identified 61 significantly altered metabolites including amino acids, fatty acids, tricarboxylic acid cycle, carbohydrates and associated intermediates. These intermediates recovered to pre-marathon related concentrations within 24 h post-marathon, except for xylose which only recovered within 48 h. Furthermore, fluctuations in cholesterol and pyrimidine intermediates indicated the activation of alternative recovery mechanisms. Metabolic recovery of the athletes was attained within 48 h post-marathon, most likely due to reduced need for fuel substrate catabolism. This may result in the activation of glycogenesis, uridine-dependent nucleotide synthesis, protein synthesis, and the inactivation of cellular autophagy. These results may be beneficial in identifying more efficient, targeted recovery approaches to improve athletic performance.

Enhanced External Counterpulsation and Recovery From a Plyometric Exercise Bout

OBJECTIVE

To analyze the effectiveness of enhanced external counterpulsation (EECP) on recovery from exercise-induced muscle damage (EIMD).

DESIGN

This study followed a crossover, placebo-controlled, counterbalanced design.

PARTICIPANTS

Ten healthy active subjects (7 male; 27 ± 4 years).

INTERVENTIONS

Participants performed a plyometric exercise bout (10 sets of 10 jumps interspersed with 1-minute rests) and were then assigned to recover for 30 minutes with either EECP (cuff pressure = 80 mm Hg) or a Sham intervention (0 mm Hg) immediately after exercise and at 24 hours after exercise. Two weeks later, they repeated the protocol with the other recovery intervention.

MAIN OUTCOME MEASURES

Muscle soreness, creatine kinase (CK) activity, jump performance, and tensiomyographic variables were measured before exercise, and 24 and 48 hours after exercise.

RESULTS

The mean jump height of the plyometric bout did not differ between EECP and Sham (P > 0.05). Exercise resulted in increased muscle soreness (P < 0.001) and CK levels (P < 0.001), as well as in impaired jump performance (P < 0.05). No changes were observed in tensiomyographic variables. No significant differences were found between interventions for any of the study outcomes.

CONCLUSIONS

No benefits on recovery from EIMD after a plyometric exercise bout were observed with EECP.

No Effect of New Zealand Blackcurrant Extract on Recovery of Muscle Damage Following Running a Half-Marathon

New Zealand blackcurrant (NZBC) contains anthocyanins, known to moderate blood flow and display anti-inflammatory properties that may improve recovery from exercise-induced muscle damage. The authors examined whether NZBC extract supplementation enhances recovery from exercise-induced muscle damage after a half-marathon race. Following a randomized, double-blind, independent groups design, 20 (eight women) recreational runners (age 30 ± 6 years, height 1.73 ± 0.74 m, body mass 68.5 ± 7.8 kg, half-marathon finishing time 1:56:33 ± 0:18:08 hr:min:s) ingested either two 300-mg/day capsules of NZBC extract (CurraNZ™) or a visually matched placebo, for 7 days prior to and 2 days following a half-marathon. Countermovement jump performance variables, urine interleukin-6, and perceived muscle soreness and fatigue were measured pre, post, and at 24 and 48 hr after the half-marathon and analyzed using a mixed linear model with statistical significance set a priori at p < .05. The countermovement jump performance variables were reduced immediately post-half-marathon (p < .05), with all returning to pre-half-marathon levels by 48 hr, except the concentric and eccentric peak force and eccentric duration, with no difference in response between groups (p > .05). Urine interleukin-6 increased 48-hr post-half-marathon in the NZBC group only (p < .01) and remained unchanged compared with pre-half-marathon levels in the placebo group (p > .05). Perceived muscle soreness and fatigue increased immediately post-half-marathon (p < .01) and returned to pre-half-marathon levels by 48 hr, with no difference between groups (p > .05). Supplementation with NZBC extract had no effect on the recovery of countermovement jump variables and perceptions of muscle soreness or fatigue following a half-marathon in recreational runners.

Effect of Sand on Landing Knee Valgus During Single-Leg Land and Drop Jump Tasks: Possible Implications for ACL Injury Prevention and Rehabilitation

CONTEXT

Despite significant emphasis on anterior cruciate ligament injury prevention, injury rates continue to rise and reinjury is common. Interventions to reduce injury have included resistance, balance, and jump training elements. The use of sand-based jump training has been postulated as an effective treatment. However, evidence on landing mechanics is limited.

OBJECTIVE

To determine potential differences in landing strategies and subsequent landing knee valgus when performing single-leg landing (SLL) and drop jump (DJ) tasks onto sand and land, and to compare between both male and female populations.

DESIGN

A randomized repeated-measures crossover design.

SETTING

University laboratory.

PARTICIPANTS

Thirty-one participants (20 males and 11 females) from a university population.

INTERVENTIONS

All participants completed DJ and SLL tasks on both sand and land surfaces.

MAIN OUTCOME MEASURES

Two-dimensional frontal plane projection angle (FPPA) of knee valgus was measured in both the DJ and SLL tasks (right and left) for both sand and land conditions.

RESULTS

FPPA was lower (moderate to large effect) for SLL in sand compared with land in both legs (left: 4.3° [2.8°]; right: 4.1° [3.8°]) for females. However, effects were unclear (left: -0.7° [2.2°]) and trivial for males (right: -1.1° [1.9°]). FPPA differences for males and females performing DJ were unclear; thus, more data is required. Differences in FPPA (land vs sand) with respect to grouping (sex) for both SLL left (4.9° [3.0°]) and right (5.1° [4.0°]) were very likely higher (small)/possibly moderate for females compared with males.

CONCLUSIONS

The effects of sand on FPPA during DJ tasks in males and females are unclear, and further data is required. However, the moderate to large reductions in FPPA in females during SLL tasks suggest that sand may provide a safer alternative to firm ground for female athletes in anterior cruciate ligament injury prevention and rehabilitation programs, which involve a SLL component.

Using Tensiomyography to Assess Changes in Knee Muscle Contraction Properties After Concentric and Eccentric Fatiguing Muscle Actions

Muñoz-López, A, De Hoyo, M, Nuñez, FJ, and Sañudo, B. Using tensiomyography to assess changes in knee muscle contraction properties after concentric and eccentric fatiguing muscle actions. J Strength Cond Res XX(X): 000-000, 2020-The purposes of this study were to analyze the effects of different types of muscle contraction (concentric and eccentric) on the passive muscular contraction properties of knee muscles and how muscle contraction can affect the muscles in different knee functions. In total, 23 active healthy men (age: 24.65 ± 1.95 years, height: 1.78 ± 0.05 m, mass: 75.33 ± 8.37 kg) participated in this study. Muscle soreness, muscle contractile properties assessed with tensiomyography (TMG) (vastus lateralis [VL] and biceps femoris [BF]), and isometric peak torque were tested before and immediately after 32 maximal repetitions of an isokinetic leg extension and flexion exercise at 180° per second. Muscle contractions were randomized to each subject's leg. From the TMG variables, only contraction velocity showed significant interactions in time × muscle × contraction (p = 0.046; partial ηp = 0.19). A greater reduction was observed in the BF (-29.03%) than in the VL (-21.25%). There was a significant decrease in contraction velocity after concentric p < 0.001, d = 1.18) and eccentric (p = 0.007, d = 0.51) exercise for the BF, while for VL, a decrease was only observed after concentric exercise (p = 0.007, d = 0.66). The leg extension exercise showed reductions in the isokinetic peak torque (p < 0.001; partial ηp = 0.83). Isometric peak torque (p < 0.001; partial ηp = 0.80) and muscle soreness (p < 0.001; partial ηp = 0.70) decreased after exercise. In conclusion, muscle mechanical properties were differently affected in relation to the muscle contraction and knee muscles involved, after a fatiguing leg extension isokinetic exercise. Isometric peak torque and muscle soreness were also reduced immediately after exercise. These results are particularly important to understand how TMG parameters are modified depending on the type of contraction.

Cryotherapy Models and Timing-Sequence Recovery of Exercise-Induced Muscle Damage in Middle- and Long-Distance Runners

CONTEXT

Among sports-recovery methods, cold-water immersion (CWI), contrast-water therapy (CWT), and whole-body cryotherapy (WBC) have been applied widely to enhance recovery after strenuous exercise. However, the different timing effects in exercise-induced muscle damage (EIMD) after these recovery protocols remain unknown.

OBJECTIVE

To compare the effects of CWI, CWT, and WBC on the timing-sequence recovery of EIMD through different indicator responses.

DESIGN

Crossover study.

SETTING

Laboratory.

PATIENTS OR OTHER PARTICIPANTS

Twelve male middle- and long-distance runners from the Beijing Sport University (age = 21.00 ± 0.95 years).

INTERVENTION(S)

Participants were treated with different recovery methods (control [CON], CWI, CWT, WBC) immediately postexercise and at 24, 48, and 72 hours postexercise.

MAIN OUTCOME MEASURE(S)

We measured perceived sensation using a visual analog scale (VAS), plasma creatine kinase (CK) activity, plasma C-reactive protein (CRP) activity, and vertical-jump height (VJH) pre-exercise, immediately postexercise, and at 1, 24, 48, 72, and 96 hours postexercise.

RESULTS

For the VAS score and CK activity, WBC exhibited better timing-sequence recovery effects than CON and CWI (P < .05), but the CWT demonstrated better effects than CON (P < .05). The CRP activity was lower after WBC than after the other interventions (P < .05). The VJH was lower after WBC than after CON and CWI (P < .05).

CONCLUSIONS

The WBC positively affected VAS, CK, CRP, and VJH associated with EIMD. The CWT and CWI also showed positive effects. However, for the activity and timing-sequence effect, CWT had weaker effects than WBC.

The Effect of L-Carnitine Supplementation on Exercise-Induced Muscle Damage: A Systematic Review and Meta-Analysis of Randomized Clinical Trials

Accumulating evidence of previous experimental studies indicated that L-Carnitine positively ameliorates muscle damage. However, findings from trials vary substantially across studies. Therefore, current meta-analysis aimed to examine the effects of L-Carnitine supplementation on exercise-induced muscle damage. An electronic search of the online literature databases (Medline (PubMed), Scopus and Google Scholar) was performed up to November 2018. Either a fixed-effects model or a random-effects model (Diasorin-Liard) was used in order to estimate the effects size. Cochran's Q test and I2 tests were used to assess the heterogeneity among the studies. Funnel plot and Egger's regression test were also employed in order to assess the publication bias. Of 604 studies, seven eligible randomized controlled trials (RCTs) were included in this meta-analysis. Pooled data from seven studies showed that L-Carnitine resulted in significant improvements in muscle soreness (MS) at the five follow-up time points (0, 24, 48, 72 and 96 hours (h)) compared to placebo. Also, pooled data indicated that L-Carnitine significantly reduced creatine kinase (CK), myoglobin (Mb), and lactate dehydrogenase (LDH) levels at one follow-up period (24 h). However, no effects have been observed beyond this period. Our outcomes indicate that L-Carnitine supplementation improves delayed-onset muscle soreness (DOMS) and markers of muscle damage. Further research is needed to clarify impacts of L-Carnitine on DOMS after different types of mechanical or chemical damages.Key teaching pointsThe effect of L-Carnitine supplementation on exercise-induced muscle damage has come under scrutiny over many years.This systematic review and meta-analyses study investigated the effects of L-Carnitine supplementation on exercise-induced muscle damage.Overall, summary results indicate that L-Carnitine supplementation improves muscle soreness and markers of muscle damage (CK, LDH, and Mb).Overall, L-carnitine supplementation ameliorated muscle damage only in resistance training groups and untrained population.

Foam rolling is an effective recovery tool in trained distance runners

Purpose

Many endurance athletes use foam rolling (FR) to decrease muscle soreness, but it is unclear whether FR effectively treats soreness in this population. Moreover, the effects of FR in highly trained runners are unknown. The aim of this study was to use downhill running (DHR) to induce muscle soreness in runners and to determine the influence of FR on soreness and running performance when compared to sham compression tights.

Methods

Participants performed a running economy (RE) test at 75% of 5-km race speed and a 3-km time trial (TT). In a crossover design, subjects then completed DHR followed by either a FR protocol or wearing sham compression tights. Two days post-DHR, subjects repeated the RE and TT tests. Crossover visits occurred 2-4 weeks later. During RE tests, VO2 and rating of perceived exertion (RPE) were recorded. Passive and active soreness were measured on a scale of 0 (no soreness) to 10 (extreme soreness).

Results

Eight runners (aged 31 ± 7 years; four females; VO2peak 57 ± 7 ml kg-1 min-1) completed the study. Both treatment conditions experienced passive (p = 0.026) and active soreness (p = 0.012) induced by DHR. Active soreness 2 days postDHR was significantly lower after FR than after sham compression tights (p = 0.025). With tights, there was a trend for an increased RPE compared to pre-DHR (p = 0.056).

Conclusions

Foam rolling decreases leg soreness in well-trained runners and attenuates soreness-related increases in perceived exertion during sub-maximal running.

Beneficial effects of a negative ion patch on eccentric exercise-induced muscle damage, inflammation, and exercise performance in badminton athletes

Complementary and alternative medicines (CAMs) are widely applied and accepted for therapeutic purposes because of their numerous benefits. Negative ion treatment belongs to one of the critical categories defined by the National Center for CAM, with such treatment capable of air purification and ameliorating emotional disorders (e.g., depression and seasonal affective disorder). Negative ions can be produced naturally and also by a material with activated energy. Exercise-induced muscle damage (EIMD) often occurs due to inadequate warm up, high-intensity exercise, overload, and inappropriate posture, especially for high-intensive competition. Few studies have investigated the effects of negative ion treatment on muscular injury in the sports science field. In the current study, we enrolled badminton athletes and induced muscle damage in them through eccentric exercise in the form of a high-intensity squat program. We evaluated the effects of negative ion patches of different intensities at three points (preexercise, postexercise, and recovery) by analyzing physiological indexes (tumor necrosis factor [TNF]-α, interleukin [IL]-6, IL-10, creatine kinase [CK], and lactate dehydrogenase [LDH] levels) and performing a functional assessment (a countermovement jump [CMJ] test). We found that a high-intensity negative ion patch could significantly reduce the levels of TNF-α, an injury-associated inflammatory cytokine, and related markers (CK and LDH). In addition, muscular overload-caused fatigue could be also ameliorated, as indicated by the functional CMJ test result, and related muscular characteristics (tone and stiffness) could be effectively improved. Thus, the negative ion treatment could effectively improve physiological adaption and muscular fatigue recovery after EIMD in the current study. The negative ion patch treatment can be further integrated into a taping system to synergistically fulfill exercise-induced damage protection and functional elevation. However, the effects of this treatment require further experimental validation.

Distinct effects of thermal treatments after lengthening contraction on mechanical hyperalgesia and exercise-induced physiological changes in rat muscle

Delayed-onset muscle soreness (DOMS) is a common but displeasing event induced by excessive muscle use or unaccustomed exercise and characterized by tenderness and movement-related pain in the exercised muscle. Thermal therapies, either icing or heating applied to muscles immediately after exercise, have been used as therapeutic interventions for DOMS. However, the mechanisms of their analgesic effects, and physiological and metabolic changes in the muscle during thermal therapy, remain unclear. In the present study, we investigated the effects of both thermal treatments on mechanical hyperalgesia of DOMS and physiological and muscle metabolite changes using the rat DOMS model induced by lengthening contraction (LC) to the gastrocnemius muscle. Heating treatment just after LC induced analgesic effects, while rats with icing treatment showed mechanical hyperalgesia similar to that of the LC group. Furthermore, increased physiological responses (e.g., muscle temperature and blood flow) following the LC were significantly kept high only in the rats with heating treatment. In addition, heating treatment increased metabolites involved in the improvement of blood flow and oxidative metabolisms in the exercised muscle. The results indicated that heating treatment just after LC has analgesic effects on DOMS, which might be mediated partly through the improvement of muscle oxidative metabolisms by changes in metabolites and elevated physiological responses.NEW & NOTEWORTHY Physiological effects of thermal therapy in the muscle and its mechanisms of analgesic effects remain unclear. The results indicated that heating, but not icing, treatment just after lengthening contractions induced analgesic effects in the rat muscle. Increases in hemodynamics, muscle temperature, and metabolites such as nicotinamide were more prominent in heating treatment, consistent with improvement of muscle oxidative metabolisms, which might reduce chemical factors to induce mechanical hyperalgesia.

Effect of Tart Cherry Concentrate on Endurance Exercise Performance: A Meta-analysis

Objective: Tart cherry concentrate has been shown to improve muscle function, and reduce muscle damage, oxidative stress/inflammation, and muscle soreness in athletes; however, evidence for acute endurance performance benefits is scarce. The purpose of this review was to evaluate the effect of tart cherry juice on endurance exercise performance with a meta-analysis.Method: Data sources included Medline, Embase, Web of Science, and Google Scholar. Eligibility criteria were randomized controlled trials with endurance exercise performance tests. Participants were healthy individuals. Interventions included tart cherry supplementation and placebo ingested before, and/or on the day of exercise. Ten studies were included (totaling 127 males and 20 females). Standardized mean differences (SMD) with 95% confidence intervals were calculated for each study and pooled effects were assessed.Results: Tart cherry concentrate in juice or powdered form, ingested for 7 days to 1.5 hours before exercise performance testing significantly improved endurance exercise performance (SMD: 0.36; 95% CI: 0.07 to 0.64; p = 0.01; I² = 0%) upon pooling of the ten studies.Conclusions: Tart cherry concentrate has a significant benefit for endurance exercise performance. Key teaching pointsTart cherry concentrate has a significant benefit for endurance exercise performance.Tart cherry concentrate may enhance endurance exercise performance via its low glycemic index, anti-inflammatory and anti-oxidative capacity, and blood flow enhancing effects.

Exercise-Induced Muscle Damage and Cardiac Stress During a Marathon Could be Associated with Dietary Intake During the Week Before the Race

Adequate food intake is important prior to endurance running competitions to facilitate adequate exercise intensity. However, no investigations have examined whether dietary intake could prevent exercise-induced muscle damage (EIMD) and cardiac stress (EICS). Thus, this study’s objective was to determine the associations between EIMD, EICS and endurance athlete diets one week before a marathon race. Sixty-nine male runners participated in this study. Food intake during the week prior to the race was collected through a seven-day weighed food record. Dietary intake on race day was also recorded. At the end of the marathon, blood samples were drawn to determine serum creatine kinase (CK) and myoglobin, and muscle–brain isoform creatine kinase (CK-MB), prohormone of brain natriuretic peptide (NT-proBNP), cardiac troponin I (TNI), and cardiac troponin T (TNT) concentration as markers of EIMD and EICS, respectively. To determine the association between these variables, a stepwise regression analysis was carried out. The dependent variable was defined as EIMD or EICS and the independent variables were defined as the number of servings within each different food group. Results showed that the intake of meat during the previous week was positively associated with post-race CK (Standardized Coefficients (β) = 0.643; p < 0.01) and myoglobin (β = 0.698; p < 0.001). Vegetables were negatively associated the concentration of post-race CK (β = −0.482; p = 0.002). Butter and fatty meat were positively associated with NT-proBNP (β = 0.796; p < 0.001) and TNI (β = 0.396; p < 0.001) post-marathon values. However, fish intake was negatively associated with CK (β = −0.272; p = 0.042), TNI (β = −0.593; p < 0.001) and TNT (β = −0.640; p = 0.002) post-marathon concentration. Olive oil was negatively associated with TNI (β = −0.536; p < 0.001) and TNT (β = −0.415; p = 0.021) values. In conclusion, the consumption of meat, butter, and fatty meat might be associated with higher levels of EIMD and EICS. On the other hand, fish, vegetables, and olive oil might have a protective role against EIMD and EICS. The selection of an adequate diet before a marathon might help to reduce some of the acute burdens associated with marathon races.

Eccentric exercise and dietary restriction inhibits M1 macrophage polarization activated by high-fat diet-induced obesity

AIMS

Obesity induce low-grade inflammation and elicit insulin resistance (IR), exercise training accompanied by a low-fat diet has been prescribed as part of the treatment for managing obesity and IR. The purpose of this study is to evaluate the effect of eccentric exercise accompanied by a low-fat diet on glycolipid metabolism, exercise capacity, and macrophage polarization in obesity-induced IR mice.

MATERIALS AND METHODS

Mice were fed with 60% high fat diet (HFD) for 12 weeks and subsequently treated with eccentric exercise or/and dietary restriction for 8 weeks. Related biochemical index were examined both before and during intervention to evaluate the ability of glycolipid metabolism. Exercise capacity was measured to verify the results of biochemical index. At 12 weeks and 12 + 8 weeks, infiltration was observed by H&E staining in adipose tissue, and macrophage polarization was detected by Immunofluorescence staining and ELISA.

KEY FINDING

1) obesity-induced IR model was established by HFD fed for 12 weeks accompanied by impaired exercise ability and increased M1 macrophage, 2) eccentric exercise accompanied by a low-fat diet markedly rescued obesity-induced IR and improved exercise capacity, 3) eccentric exercise accompanied by a low-fat diet markedly inhibited M1 macrophage polarization and activated M2 macrophage.

SIGNIFICANCE

Eccentric exercise accompanied by a low-fat diet rescued obesity-induced IR and improved exercise capacity, which were associated with the inhibition of M1 macrophage polarization and the activation of M2 macrophage. These indicate that macrophage polarization provides the potential target of intervention for inflammation and IR in obesity.

The effect of low level laser irradiation on oxidative stress, muscle damage and function following neuromuscular electrical stimulation. A double blind, randomised, crossover trial

BACKGROUND

Low level laser therapy (LLLT) is among novel methods for preventing and treating muscle damage and soreness induced by volitional exercise, but little is known about using LLLT before neuromuscular electrical stimulation. The aim of this first randomised, double blind, crossover trial addressing this issue was to evaluate effects of LLLT on muscle damage and oxidative stress, as well as recovery of muscle function after a single session of isometric neuromuscular electrical stimulation(NMES).

METHODS

Twenty four moderately active, healthy men aged 21-22 years received 45 electrically evoked tetanic, isometric contractions of the quadriceps femoris, preceded by LLLT or sham-LLLT. Maximal isometric voluntary muscle torques, perceived soreness, and blood samples were analysed from baseline to 96 h post intervention. We measured plasma markers of muscle damage (the activity of creatine kinase), and inflammation (C-reactive protein), and evaluated redox state parameters.

RESULTS

NMES-evoked contractions induced oxidative stress, demonstrated by an increase in lipid peroxidation and impairments in enzymatic antioxidant system. LLLT irradiations had a protective effect on NMES-induced decrease in enzymatic antioxidant defence and shortened the duration of inflammation. This effect of irradiations on redox state and inflammation did not affect lipid peroxidation, muscle damage, and muscle torque.

CONCLUSIONS

LLLT may protect from impairments in enzymatic antioxidant system and may shorten inflammation induced by a single NMES session in moderately active, healthy men. However, the effects of LLLT on redox state and inflammatory processes do not seem to affect muscle damage and recovery of muscle function after NMES.

TRIAL REGISTRATION

The study was retrospectively registered in the Australian New Zealand Clinical Trials Registry (ANZCTR); The trial registration number: ACTRN12619000678190; date of registration: 6 May 2019.

Prolonged cooling with phase change material enhances recovery and does not affect the subsequent repeated bout effect following exercise

PURPOSE

The aim of this investigation was twofold: (1) to examine the effect of prolonged phase change material (PCM) cooling following eccentric exercise of the quadriceps on indices of muscle damage, and (2) to elucidate whether application of PCM cooling blunted the acute adaptive response to eccentric exercise, known as the repeated bout effect (RBE).

METHODS

Twenty-six males (25 ± 6 years) performed an initial bout (B1) of 120 eccentric quadriceps contractions on each leg at 90% of their isometric strength and were then randomized to receive PCM packs frozen at 15 °C (treatment) or melted packs (control) worn directly on the skin under shorts for 6 h. The protocol was repeated 14 days later (B2) with all participants receiving the control condition.

RESULTS

PCM cooling provided protection against strength loss in B1 (P = 0.005) with no difference in strength between treatment groups in B2 (P = 0.172; bout by treatment by time P = 0.008). PCM cooling reduced soreness in B1 (P = 0.009) with no difference between treatment groups in B2 (P = 0.061). Soreness was overall lower following B2 than B1 (P < 0.001). CK was elevated in B1 (P < 0.0001) and reduced in B2 (P < 0.001) with no difference between treatments. The damage protocol did not elevate hsCRP in B1, with no difference between treatments or between bouts.

CONCLUSIONS

This work provides further evidence that PCM cooling enhances recovery of strength and reduces soreness following eccentric exercise. Importantly, these data show for the first time that prolonged PCM cooling does not compromise the adaptive response associated with the RBE.

Nutritional and Pharmacological Interventions to Expedite Recovery Following Muscle-Damaging Exercise in Older Adults: A Narrative Review of the Literature

Exercise-induced muscle damage (EIMD) manifests as muscle soreness, inflammation, and reductions in force generating capacity that can last for several days after exercise. The ability to recover and repair damaged tissues following EIMD is impaired with age, with older adults (≥50 years old) experiencing a slower rate of recovery than their younger counterparts do for the equivalent exercise bout. This narrative review discusses the literature examining the effect of nutritional or pharmacological supplements taken to counter the potentially debilitating effects of EIMD in older adults. Studies have assessed the effects of nonsteroidal anti-inflammatory drugs, vitamin C and/or E, or higher protein diets on recovery in older adults. Each intervention showed some promise for attenuating EIMD, but, overall, there is a paucity of available data in this population, and more studies are required to determine the influence of nutrition or pharmacological interventions on EIMD in older adults.

High-Frequency Resistance Training Is Not More Effective Than Low-Frequency Resistance Training in Increasing Muscle Mass and Strength in Well-Trained Men

Gomes, GK, Franco, CM, Nunes, PRP, and Orsatti, FL. High-frequency resistance training is not more effective than low-frequency resistance training in increasing muscle mass and strength in well-trained men. J Strength Cond Res 33(7S): S130-S139, 2019-We studied the effects of 2 different weekly frequency resistance training (RT) protocols over 8 weeks on muscle strength and muscle hypertrophy in well-trained men. Twenty-three subjects (age: 26.2 ± 4.2 years; RT experience: 6.9 ± 3.1 years) were randomly allocated into the 2 groups: low-frequency resistance training (LFRT, n = 12) or high-frequency resistance training (HFRT, n = 11). The LFRT performed a split-body routine, training each specific muscle group once a week. The HFRT performed a total-body routine, training all muscle groups every session. Both groups performed the same number of sets (10-15 sets) and exercises (1-2 exercise) per week, 8-12 repetitions maximum (70-80% of 1 repetition maximum [1RM]), 5 times per week. Muscle strength (bench press and squat 1RM) and lean tissue mass (dual-energy x-ray absorptiometry) were assessed before and at the end of the study. Results showed that both groups improved (p < 0.001) muscle strength {LFRT and HFRT: bench press = 5.6 kg (95% confidence interval [CI]: 1.9-9.4) and 9.7 kg (95% CI: 4.6-14.9) and squat = 8.0 kg (95% CI: 2.7-13.2) and 12.0 kg (95% CI: 5.1-18.1), respectively} and lean tissue mass (p = 0.007) (LFRT and HFRT: total body lean mass = 0.5 kg [95% CI: 0.0-1.1] and 0.8 kg [95% CI: 0.0-1.6], respectively) with no difference between groups (bench press, p = 0.168; squat, p = 0.312, and total body lean mass, p = 0.619). Thus, HFRT and LFRT are similar overload strategies for promoting muscular adaptation in well-trained subjects when the sets and intensity are equated per week.

Impact of anthocyanin-rich whole fruit consumption on exercise-induced oxidative stress and inflammation: a systematic review and meta-analysis

CONTEXT

Supplementing with fruits high in anthocyanins to reduce exercise-induced oxidative stress and inflammation has produced mixed results.

OBJECTIVE

This systematic review and meta-analysis aims to discuss the impact of whole fruits high in anthocyanins, including processing methods and the type and amount of fruit, on inflammation and oxidative stress.

DATA SOURCES

PICOS reporting guidelines and a customized coding scheme were used to search 5 databases (SPORTDiscus, Science Direct, Web of Science [BIOSIS], Medline [Pubmed], and the Cochrane Collaboration) with additional cross-referencing selection.

DATA EXTRACTION

A random-effects meta-analysis was used to measure effects of the fruit supplements with 3 statistics; the QTotal value based on a χ2 distribution, τ2 value, and I2 value were used to determine homogeneity of variances on 22 studies (out of 807). Outliers were identified using a relative residual value.

RESULTS

A small significant negative summary effect across the sum of all inflammatory marker outcomes (P < 0.001) and a moderate negative effect for the sum of all oxidative stress marker outcomes (P = 0.036) were found. Moderator analyses did not reveal significant (P > 0.05) differences between subgrouping variables.

CONCLUSIONS

Results indicate that consumption of whole fruit high in anthocyanins can be beneficial for reducing inflammation and oxidative stress.

The Effects of Leucine-Enriched Branched-Chain Amino Acid Supplementation on Recovery After High-Intensity Resistance Exercise

Context: Of the 3 branched-chain amino acids (BCAA), leucine has arguably received the most attribution for the role of BCAA supplementation in alleviating symptoms of exercise-induced muscle damage and facilitation of acute performance recovery. Purpose: To examine whether enrichment of a standard BCAA supplement with additional leucine or a standalone leucine (LEU) supplement differentially affects exercise-induced muscle damage and performance recovery compared with a standard BCAA supplement. Methods: A total of 22 recreationally active male and female subjects were recruited and assigned to consume a BCAA, leucine-enriched BCAA (LBCAA), or LEU supplement for 11 d. On the eighth day, subjects performed eccentric-based resistance exercise (ECRE). Lower-body mean average and peak power, plasma creatine kinase, soreness, and pain threshold were measured before and 24, 48, and 72 h after ECRE. Results: LEU showed decreased mean average power (P = .02) and mean peak power (P = .01) from baseline to 48 h post-ECRE, whereas LBCAA and BCAA only trended toward a reduction at 24 hours post-ECRE. At 48 h post-ECRE, BCAA showed greater recovery of mean peak power than LEU (P = .04). At 24 h post-ECRE, LEU demonstrated a greater increase in plasma creatine kinase from baseline than BCAA (P = .04). Area under the curve for creatine kinase was greater in LEU than BCAA (P = .02), whereas BCAA and LBCAA did not differ. Only LEU demonstrated increased soreness during rest and under muscular tension at 24 and 48 h post-ECRE (P < .05). Conclusions: LBCAA failed to afford any advantages over a standard BCAA supplement for postexercise muscle recovery, whereas a LEU supplement was comparatively ineffective.

Eight Weeks of a High Dose of Curcumin Supplementation May Attenuate Performance Decrements Following Muscle-Damaging Exercise

BACKGROUND

It is known that unaccustomed exercise-especially when it has an eccentric component-causes muscle damage and subsequent performance decrements. Attenuating muscle damage may improve performance and recovery, allowing for improved training quality and adaptations. Therefore, the current study sought to examine the effect of two doses of curcumin supplementation on performance decrements following downhill running.

METHODS

Sixty-three physically active men and women (21 ± 2 y; 70.0 ± 13.7 kg; 169.3 ± 15.2 cm; 25.6 ± 14.3 body mass index (BMI), 32 women, 31 men) were randomly assigned to ingest 250 mg of CurcuWIN® (50 mg of curcuminoids), 1000 mg of CurcuWIN® (200 mg of curcuminoids), or a corn starch placebo (PLA) for eight weeks in a double-blind, randomized, placebo-controlled parallel design. At the end of the supplementation period, subjects completed a downhill running protocol intended to induce muscle damage. Muscle function using isokinetic dynamometry and perceived soreness was assessed prior to and at 1 h, 24 h, 48 h, and 72 h post-downhill run.

RESULTS

Isokinetic peak extension torque did not change in the 200-mg dose, while significant reductions occurred in the PLA and 50-mg groups through the first 24 h of recovery. Isokinetic peak flexion torque and power both decreased in the 50-mg group, while no change was observed in the PLA or 200-mg groups. All the groups experienced no changes in isokinetic extension power and isometric average peak torque. Soreness was significantly increased in all the groups compared to the baseline. Non-significant improvements in total soreness were observed for the 200-mg group, but these changes failed to reach statistical significance.

CONCLUSION

When compared to changes observed against PLA, a 200-mg dose of curcumin attenuated reductions in some but not all observed changes in performance and soreness after completion of a downhill running bout. Additionally, a 50-mg dose appears to offer no advantage to changes observed in the PLA and 200-mg groups.

No Effect of Tart Cherry Juice or Pomegranate Juice on Recovery from Exercise-Induced Muscle Damage in Non-Resistance Trained Men

Tart cherry juice (TC) and pomegranate juice (POM) have been demonstrated to reduce symptoms of exercise-induced muscle damage (EIMD), but their effectiveness has not been compared. This randomized, double-blind, parallel study compared the effects of TC and POM on markers of EIMD. Thirty-six non-resistance trained men (age 24.0 (Interquartile Range (IQR) 22.0, 33.0) years, body mass index (BMI) 25.6 ± 4.0 kg·m^-2) were randomly allocated to consume 2 × 250 mL of: TC, POM, or an energy-matched fruit-flavored placebo drink twice daily for nine days. On day 5, participants undertook eccentric exercise of the elbow flexors of their non-dominant arm. Pre-exercise, immediately post-exercise, and at 24 h, 48 h, 72 h and 96 h post-exercise, maximal isometric voluntary contraction (MIVC), delayed onset muscle soreness (DOMS), creatine kinase (CK), and range of motion (ROM) were measured. The exercise protocol induced significant decreases in MIVC (p < 0.001; max decrease of 26.8%, 24 h post-exercise) and ROM (p = 0.001; max decrease of 6.8%, 72 h post-exercise) and significant increases in CK (p = 0.03; max increase 1385 U·L^-1, 96 h post-exercise) and DOMS (p < 0.001; max increase of 26.9 mm, 48 h post-exercise). However, there were no statistically significant differences between treatment groups (main effect of group p > 0.05 or group x time interaction p > 0.05). These data suggest that in non-resistance trained men, neither TC nor POM enhance recovery from high-force eccentric exercise of the elbow flexors.

Photobiomodulation Therapy Does Not Attenuate Fatigue and Muscle Damage in Judo Athletes: A Randomized, Triple-Blind, Placebo-Controlled Trial

Fatigue and muscle damage negatively affect performance in lower limb exercises involving the stretch-shortening cycle in judo athletes during competition and training sessions. Photobiomodulation therapy has emerged as an effective non-invasive strategy to attenuate fatigue and muscle damage when applied before different types of exercises. Our objective was to investigate the effects of photobiomodulation therapy on fatigue and muscle damage in judo athletes. Sixteen judo athletes participated in the study (23.1 ± 3.8 years, 77.9 ± 14.9 kg, 173.1 ± 8.9 cm, 17.5 ± 7.3 body fat%, 12.9 ± 5.0 years of practice). Each participant received, in a randomized manner, photobiomodulation in one limb and placebo in the contralateral limb on the same day. Thereafter, subjects performed a stretch-shortening cycle protocol to induce muscle fatigue and damage. Countermovement jump (impulse, peak power, peak velocity, and peak force), echo intensity (rectus femoris and vastus lateralis), and muscle soreness were assessed at different time points before, during, immediately post, and 24 and 48 h after the protocol. Muscle fatigue was detected due to reductions in countermovement jump impulse (14.7 ± 9.8 and 15.9 ± 15.5%), peak power (12.9 ± 8.5 and 11.9 ± 6.9%), peak velocity (8.6 ± 8.1 and 6.5 ± 6.0%), and peak force (7.0 ± 5.3 and 8.0 ± 6.1%) after the protocol (p < 0.001), for placebo and photobiomodulation therapy, respectively. Muscle damage was detected due to reductions in countermovement jump impulse (−6.1 ± 19.2% and −4.5 ± 9.2%, p < 0.05), increases in echo intensity (rectus femoris, 21.0 ± 11.9 and 20.8 ± 9.0%; and vastus lateralis, 22.4 ± 23.2%; and 16.7 ± 23.8%; p < 0.001), and quadriceps muscle soreness (3.6 ± 1.6 and 3.5 ± 1.7 a.u; p < 0.011), 48 h after the protocol, for placebo and photobiomodulation therapy, respectively. No differences were observed between photobiomodulation therapy and placebo at any time points for any variables (p > 0.05), indicating no positive effect favoring photobiomodulation therapy. In conclusion, our findings suggest no effect of photobiomodulation therapy applied before exercise to reduce lower limb muscle fatigue and damage during and following a stretch-shortening cycle protocol in judo athletes.

Acid sphingomyelinase inhibition alleviates muscle damage in gastrocnemius after acute strenuous exercise

[Purpose]

Strenuous exercise often induces skeletal muscle damage, which results in impaired performance. Sphingolipid metabolism contributes to various cellular processes, including apoptosis, stress response, and inflammation. However, the relationship between exercise-induced muscle damage and ceramide (a key component of sphingolipid metabolism), is rarely studied. The present study aimed to explore the regulatory role of sphingolipid metabolism in exercise-induced muscle damage.

[Methods]

Mice were subjected to strenuous exercise by treadmill running with gradual increase in intensity. The blood and gastrocnemius muscles (white and red portion) were collected immediately after and 24 h post exercise. For 3 days, imipramine was intraperitoneally injected 1 h prior to treadmill running.

[Results]

Interleukin 6 (IL-6) and serum creatine kinase (CK) levels were enhanced immediately after and 24 h post exercise (relative to those of resting), respectively. Acidic sphingomyelinase (A-SMase) protein expression in gastrocnemius muscles was significantly augmented by exercise, unlike, serine palmitoyltransferase-1 (SPT-1) and neutral sphingomyelinase (N-SMase) expressions. Furthermore, imipramine (a selective A-SMase inhibitor) treatment reduced the exercise-induced CK and IL-6 elevations, along with a decrease in cleaved caspase-3 (Cas-3) of gastrocnemius muscles.

[Conclusion]

We found the crucial role of A-SMase in exercise-induced muscle damage.

The Effect of Phase Change Material on Recovery of Neuromuscular Function Following Competitive Soccer Match-Play

Aim: Cryotherapy is commonly implemented following soccer match-play in an attempt to accelerate the natural time-course of recovery, but the effect of this intervention on neuromuscular function is unknown. The aim of the present study was to examine the effect of donning lower-body garments fitted with cooled phase change material (PCM) on recovery of neuromuscular function following competitive soccer match-play.

Methods: Using a randomized, crossover design, 11 male semi-professional soccer players wore PCM cooled to 15°C (PCM_cold) or left at ambient temperature (PCM_amb; sham control) for 3 h following soccer match-play. Pre-, and 24, 48, and 72 h post-match, participants completed a battery of neuromuscular, physical, and perceptual tests. Maximal voluntary contraction force (MVC) and twitch responses to electrical (femoral nerve) and magnetic (motor cortex) stimulation (TMS) during isometric knee-extension and at rest were measured to assess central nervous system (CNS) (voluntary activation, VA) and muscle contractile (quadriceps potentiated twitch force, Q_tw,pot) function. Fatigue and perceptions of muscle soreness were assessed via visual analog scales, and physical function was assessed through measures of jump [countermovement jump (CMJ) height and reactive strength index (RSI)] performance. A belief questionnaire was completed pre- and post-intervention to determine the perceived effectiveness of each garment.

Results: Competitive soccer match-play elicited persistent decrements in MVC, VA measured with femoral nerve stimulation, Q_tw,pot, as well as reactive strength, fatigue and muscle soreness (P < 0.05). Both MVC and VA were higher at 48 h post-match after wearing PCM_cold compared with PCM_amb (P < 0.05). However, there was no effect of PCM on the magnitude or time-course of recovery for any other neuromuscular, physical function, or perceptual indices studied (P > 0.05). The belief questionnaire revealed that players perceived that both PCM_cold and PCM_amb were moderately effective in improving recovery, with no difference between the two interventions (P = 0.56).

Conclusion: Although wearing cooled PCM garments improved MVC and VA 48 h following match-play, the lack of effect on measures of physical function or perceptual responses to match-play suggest that PCM offers a limited benefit to the recovery process. The lack of effect could have been due to the relatively small magnitude of change in most of the outcome measures studied.

Eccentric Muscle Contractions: Risks and Benefits

Eccentric contractions, characterized by the lengthening of the muscle-tendon complex, present several unique features compared with other types of contractions, which may lead to unique adaptations. Due to its specific physiological and mechanical properties, there is an increasing interest in employing eccentric muscle work for rehabilitation and clinical purposes. However, unaccustomed eccentric exercise is known to cause muscle damage and delayed pain, commonly defined as “Delayed-Onset Muscular Soreness” (DOMS). To date, the most useful preventive strategy to avoid these adverse effects consists of repeating sessions involving submaximal eccentric contractions whose intensity is progressively increased over the training. Despite an increased number of investigations focusing on the eccentric contraction, a significant gap still remains in our understanding of the cellular and molecular mechanisms underlying the initial damage response and subsequent adaptations to eccentric exercise. Yet, unraveling the molecular basis of exercise-related muscle damage and soreness might help uncover the mechanistic basis of pathological conditions as myalgia or neuromuscular diseases. In addition, a better insight into the mechanisms governing eccentric training adaptations should provide invaluable information for designing therapeutic interventions and identifying potential therapeutic targets.

Investigation of the Impact of Below-Knee Compression Garments on Markers of Exercise-Induced Muscle Damage and Performance in Endurance Runners: A Prospective Randomized Controlled Trial

BACKGROUND

Compression garment utilization is very popular among runners despite a lack of consensus in the literature regarding a beneficial impact. The aim of the study was to investigate the impact of training and competing with compression garments on exercise-induced muscle damage and performance in ultramarathon runners.

HYPOTHESIS

Compression garments will reduce the severity of exercise-induced muscle damage and improve performance in long-distance runners compared with control conditions.

STUDY DESIGN

Prospective, randomized controlled trial.

LEVEL OF EVIDENCE

Level 1.

METHODS

The study was conducted in healthy, uninjured endurance runners (n = 41) participating in a 56-km ultramarathon. The experimental group (n = 20; 14 males, 6 females) trained for 6 weeks and participated in the race wearing below-knee compression garments while the control group (n = 21; 15 males, 6 females) did not. Participants were tested on 4 occasions for various markers of exercise-induced muscle damage and running performance.

RESULTS

Ankle circumference measurements increased significantly less ( P = 0.01, Cohen d = 0.9) in the experimental group from immediately after until 2 days post-race compared with the control group. No further statistically significant changes were detected over time in midcalf circumferences, muscle architecture, or race performance. Selected pain ratings were statistically significant and worse in the experimental group.

CONCLUSION

There are limited indications of a beneficial impact of compression garments with improvements in ankle circumference measurements. No ergogenic impact was detected.

CLINICAL RELEVANCE

There is limited evidence to support the continued utilization of commercially available below-knee compression garments during running for the purpose of muscle recovery or as a performance aid.

Cold water immersion improves recovery of sprint speed following a simulated tournament

It is a common requirement in tournament scenarios for athletes to compete multiple times in a relatively short time period, with insufficient recovery time not allowing full restoration of physical performance. This study aimed to develop a greater understanding of the physiological stress experienced by athletes in a tournament scenario, and how a commonly used recovery strategy, cold water immersion (CWI), might influence these markers. Twenty-one trained male games players (age 19 ± 2; body mass 78.0 ± 8.8 kg) were randomised into a CWI group (n = 11) or a control group (n = 10). To simulate a tournament, participants completed the Loughborough Intermittent Shuttle Test (LIST) on three occasions in five days. Recovery was assessed at specific time points using markers of sprint performance, muscle function, muscle soreness and biochemical markers of damage (creatine kinase, CK), inflammation (IL-6 and C-Reactive Protein) and oxidative stress (lipid hydroperoxides and activity of 6 lipid-soluble antioxidants). The simulated tournament was associated with perturbations in some, but not all, markers of physiological stress and recovery. Cold water immersion was associated with improved recovery of sprint speed 24 h after the final LIST (ES = 0.83 ± 0.59; p = .034) and attenuated the efflux of CK pre- and post-LIST 3 (p < .01). The tournament scenario resulted in an escalation of physiological stress that, in the main, cold water immersion was ineffective at managing. These data suggest that CWI is not harmful, and provides limited benefits in attenuating the deleterious effects experienced during tournament scenarios.

Assessing the usefulness of acute physiological responses following resistance exercise: sensitivity, magnitude of change, and time course of measures

A variety of strategies exist to modulate the acute physiological responses following resistance exercise aimed at enhancing recovery and/or adaptation processes. To assess the true impact of these strategies, it is important to know the ability of different measures to detect meaningful change. We investigated the sensitivity of measures used to quantify acute physiological responses to resistance exercise and constructed a physiological profile to characterise the magnitude of change and the time course of these responses. Eight males accustomed to regular resistance exercise performed experimental sessions during a “control week”, void of an exercise stimulus. The following week, termed the “exercise week”, participants repeated this sequence of experimental sessions, and they also performed a bout of lower-limb resistance exercise following the baseline assessments. Assessments were conducted at baseline and at 2, 6, 24, 48, 72, and 96 h after the intervention. On the basis of the signal-to-noise ratio, the most sensitive measures were maximal voluntary isometric contraction, 20-m sprint, countermovement jump peak force, rate of force development (100–200 ms), muscle soreness, Daily Analysis Of Life Demands For Athletes part B, limb girth, matrix metalloproteinase-9, interleukin-6, creatine kinase, and high-sensitivity C-reactive protein with ratios >1.5. Clear changes in these measures following resistance exercise were determined via magnitude-based inferences. These findings highlight measures that can detect real changes in acute physiological responses following resistance exercise in trained individuals. Researchers investigating strategies to manipulate acute physiological responses for recovery and/or adaptation can use these measures, as well as the recommended sampling points, to be confident that their interventions are making a worthwhile impact.

Effect of a leucine-enriched essential amino acids mixture on muscle recovery

[Purpose] The aim of this study was to determine whether the consumption of a leucine-enriched essential amino acid mixture (LEAA), which is known to increase protein synthesis in muscles, alleviates muscle damage and accelerates recovery by ameliorating muscle damage. [Participants and Methods] A double-blind, randomized crossover trial was conducted over a 5-week period. Ten untrained males (age, 23.0 ± 1.6 years) were asked to repeatedly flex and extend their elbows for 10 counts/set × 5 sets at full power while using a dynamometer. The participants took 3.6-g supplements (LEAA mixture or placebo) 3 times daily on day 0 and for the next 7 days. Changes in serum creatine phosphokinase (CPK) activity and myoglobin concentration as markers of muscle tissue damage were evaluated prior to and after exercise and on days 1, 2, 3, 5, and 7. [Results] The relative ratio of the changes in peak serum CPK activity measured on day 5 was significantly lower after taking LEAA than after taking the placebo. [Conclusion] LEAA consumption suppressed exercise-induced elevation of muscle damage markers in blood, which suggests that LEAA could attenuate muscle damage and aid muscle recovery.

The Beneficial Effects of Lactobacillus plantarum PS128 on High-Intensity, Exercise-Induced Oxidative Stress, Inflammation, and Performance in Triathletes

A triathlon, which consists of swimming, bicycling, and running, is a high-intensity and long-term form of exercise that can cause injuries such as muscular damage, inflammation, oxidative stress, and energy imbalance. Probiotics are thought to play an important role in disease incidence, health promotion, and nutrient metabolism, but only a few studies have focused on physiological adaptations to exercise in sports science. Previous studies indicated that Lactobacillus supplementation could improve oxidative stress and inflammatory responses. We investigate the effects of Lactobacillus plantarum PS128 supplementation on triathletes for possible physiological adaptation. The triathletes were assigned to one of two groups with different exercise intensity stimulations with different time-points to investigate the effects of body compositions, inflammation, oxidative stress, performance, fatigue, and injury-related biochemical indices. L. plantarum PS128 supplementation, combined with training, can significantly alleviate oxidative stress (such as creatine kinase, Thioredoxin, and Myeloperoxidase indices) after a triathlon (p < 0.05). This effect is possibly regulated by a 6–13% decrease of indicated pro-inflammation (TNF-α, IL-6, and IL-8) cytokines (p < 0.05) and 55% increase of anti-inflammation (IL-10) cytokines (p < 0.05) after intensive exercise stimulation. In addition, L. plantarum PS128 can also substantially increase 24–69% of plasma-branched amino acids (p < 0.05) and elevate exercise performance, as compared to the placebo group (p < 0.05). In conclusion, L. plantarum PS128 may be a potential ergogenic aid for better training management, physiological adaptations to exercise, and health promotion.

Effect of Caffeine Supplementation on Quadriceps Performance After Eccentric Exercise

Green, MS, Martin, TD, and Corona, BT. Effect of caffeine supplementation on quadriceps performance after eccentric exercise. J Strength Cond Res 32(10): 2863-2871, 2018-Caffeine use is common among athletes seeking to capitalize on its potential ergogenic effects. Limited research has examined caffeine's effects when used after activities that resulted in exercise-induced muscle damage (EIMD). This study examined the effect of caffeine supplementation on uninjured and injured muscle. Eight men and women (N = 16) who were physically active individuals participated in this study (age: 24.3 ± 4.3 years; height: 173.0 ± 7.0 cm, mass: 75.2 ± 11.5 kg; body fat: 18.2 ± 15.9%). One leg was assessed under uninjured and injured (100 eccentric quadriceps contractions) conditions after caffeine supplementation (6 mg·kg), with the other leg assessed under both conditions after placebo supplementation. Compared with the placebo, caffeine increased peak isokinetic torque by 6.8 ± 2.3 and 9.4 ± 2.5% in uninjured and injured muscle, respectively, but had no effect on maximal voluntary isometric torque or fatigue index in uninjured or injured muscle, with treatments exhibiting similar (p > 0.05) alterations in isometric torque (-11.9 ± 2.2%), fatigue index (-13.9 ± 3.4%), and soreness (+44.0 ± 4.7) after eccentric contractions. The results of this study suggest that caffeine possesses a similar ergogenic effect on isokinetic torque in both uninjured and injured states, but no effect on the production of isometric torque, perception of soreness, or degree of relative fatigue. Athletes should consider the potential caffeine supplementation possesses during recovery from activities that resulted in EIMD.

Nutritional and Supplementation Strategies to Prevent and Attenuate Exercise-Induced Muscle Damage: a Brief Review

Exercise-induced muscle damage (EIMD) is typically caused by unaccustomed exercise and results in pain, soreness, inflammation, and reduced muscle function. These negative outcomes may cause discomfort and impair subsequent athletic performance or training quality, particularly in individuals who have limited time to recover between training sessions or competitions. In recent years, a multitude of techniques including massage, cryotherapy, and stretching have been employed to combat the signs and symptoms of EIMD, with mixed results. Likewise, many varied nutritional and supplementation interventions intended to treat EIMD-related outcomes have gained prominence in the literature. To date, several review articles have been published that explore the many recovery strategies purported to minimize indirect markers of muscle damage. However, these articles are very limited from a nutritional standpoint. Thus, the purpose of this review is to briefly and comprehensively summarize many of these strategies that have been shown to positively influence the recovery process after damaging exercise. These strategies have been organized into the following sections based on nutrient source: fruits and fruit-derived supplements, vegetables and plant-derived supplements, herbs and herbal supplements, amino acid and protein supplements, vitamin supplements, and other supplements.

Effects of oat protein supplementation on skeletal muscle damage, inflammation and performance recovery following downhill running in untrained collegiate men

The positive influence of animal-based protein supplementation during muscle-damaging exercise has been widely studied. However, the effects of plant-based proteins remain unclear and require further clarification. This study investigated the protective role of oat protein against exercise induced muscle damage (EIMD), subsequent inflammation, and loss of performance induced by downhill running. Subjects consumed either oat protein (25 g protein) or a placebo for 14 days prior to a downhill running test and then for 4 days thereafter. Treatments with oat protein for 19 days markedly alleviated eccentric exercise induced skeletal muscle soreness, and reduced the elevation of plasma IL-6 concentrations and serum creatine kinase, myoglobin and C reactive protein contents. In addition, oat protein supplementation significantly inhibited limb edema following damaging exercise, and the adverse effects on muscle strength, knee-joint range of motion, and vertical jump performance were lessened. Furthermore, the administration of oat protein facilitated recovery from exhaustive downhill running in this study. These findings demonstrated that oat protein supplementation has the potential to alleviate the negative effects of eccentric exercise in untrained young males.

AmLexin, a Standardized blend of Acacia catechu and Morus alba, shows benefits to delayed onset muscle soreness in healthy runners

[Purpose]

Sudden and exhaustive exercise causes muscle damage accompanied by oxidative stress and inflammation, leading to muscle fatigue and soreness. AmLexin contains a standardized blend of extracts from the heartwood of Acacia catechu and the root bark of Morus alba, and is known to possess antioxidant and anti-inflammatory properties. The aim of this study was to investigate the effects of this proprietary blend supplementation on muscular pain and redox balance in healthy runners, in comparison to a placebo.

[Methods]

A double-blind placebo-controlled clinical trial was carried out over 9 weeks in a single center. Thirty physically active male and female subjects within 18−70 years of age were randomized into AmLexin (mean age = 42.92 ± 2.48 and gender 7/5, male/female, respectively) and placebo (mean age = 41.15 ± 3.5 and gender 10/3, male/female, respectively) groups. Subjects were supplemented with 400 mg of AmLexin/day or a look-alike placebo during an 8-week training program, and for one week following a 13.1-mile half-marathon. Twenty-six subjects completed the 9-week supplementation trial.

[Results]

Results showed the AmLexin group experienced significantly lower levels of post-exercise pain on day 1−3 following the half-marathon compared to the placebo group. The AmLexin group also showed lower post-exercise oxidative stress and higher antioxidant capacity on days 1 and 6 following the half-marathon. These results demonstrated the rapid benefits of AmLexin on pain and oxidative stress within 1−6 days post-exercise.

[Conclusion]

Our data suggest that AmLexin could be a safe, effective botanical alternative for delayed onset muscle soreness.

Flavanol-Rich Cacao Mucilage Juice Enhances Recovery of Power but Not Strength from Intensive Exercise in Healthy, Young Men

(1) Background: Mucilage within cacao pods contains high levels of polyphenols. We investigated whether consumption of cacao juice enhances the recovery of muscle function following intensive knee extension exercise. (2) Methods: Ten recreationally active males completed two trials of 10 sets of 10 single leg knee extensions at ~80% one repetition maximum. Participants consumed each supplement (ZumoCacao^® juice, CJ or a dextrose drink, PL) for 7 days prior to and 48 h post exercise. Knee extension maximum voluntary contraction (MVC) and a counter movement jump (CMJ) were performed at baseline, immediately, 24 h, and 48 h post-exercise. Venous blood samples were collected at each time point and analyzed for indices of inflammation, oxidative damage, and muscle damage. (3) Results: CMJ height recovered faster with CJ at 24 h and 48 h post-exercise (p < 0.05), but there was no effect of CJ on recovery of MVC (both p > 0.05). There was also no effect of the trial on any blood markers (all p > 0.05). (4) Conclusions: Supplementation with CJ for 7 days prior to and 2 days after intensive knee extensor exercise improved functional recovery as shown by an improved recovery of CMJ up to 48 h post-exercise. However, the precise mechanism of action is unclear and requires further investigation.

Are There Limitations to Exercise Benefits in Peripheral Arterial Disease?

Substantial evidence exists indicating that inactivity contributes to the progression of chronic disease, and conversely, that regular physical activity can both prevent the onset of disease as well as delay the progression of existing disease. To that end "exercise as medicine" has been advocated in the broad context as general medical care, but also in the specific context as a therapeutic, to be considered in much the same way as other drugs. As there are non-responders to many medications, there also are non-responders to exercise; individual who participate but do not demonstrate appreciable improvement/benefit. In some settings, the stress induced by exercise may aggravate an underlying condition, rather than attenuate chronic disease. As personalized medicine evolves with ready access to genetic information, so too will the incorporation of exercise in the context of those individual genetics. The focus of this brief review is to distinguish between the inherent capacity to perform, as compared to adaptive response to active exercise training in relation to cardiovascular health and peripheral arterial disease.

The Influence of Post-Exercise Cold-Water Immersion on Adaptive Responses to Exercise: A Review of the Literature

Post-exercise cold-water immersion (CWI) is used extensively in exercise training as a means to minimise fatigue and expedite recovery between sessions. However, debate exists around its merit in long-term training regimens. While an improvement in recovery following a single session of exercise may improve subsequent training quality and stimulus, reports have emerged suggesting CWI may attenuate long-term adaptations to exercise training. Recent developments in the understanding of the molecular mechanisms governing the adaptive response to exercise in human skeletal muscle have provided potential mechanistic insight into the effects of CWI on training adaptations. Preliminary evidence suggests that CWI may blunt resistance signalling pathways following a single exercise session, as well as attenuate key long-term resistance training adaptations such as strength and muscle mass. Conversely, CWI may augment endurance signalling pathways and the expression of genes key to mitochondrial biogenesis following a single endurance exercise session, but have little to no effect on the content of proteins key to mitochondrial biogenesis following long-term endurance training. This review explores current evidence regarding the underlying molecular mechanisms by which CWI may alter cellular signalling and the long-term adaptive response to exercise in human skeletal muscle.

Implications of Impaired Endurance Performance following Single Bouts of Resistance Training: An Alternate Concurrent Training Perspective

A single bout of resistance training induces residual fatigue, which may impair performance during subsequent endurance training if inadequate recovery is allowed. From a concurrent training standpoint, such carry-over effects of fatigue from a resistance training session may impair the quality of a subsequent endurance training session for several hours to days with inadequate recovery. The proposed mechanisms of this phenomenon include: (1) impaired neural recruitment patterns; (2) reduced movement efficiency due to alteration in kinematics during endurance exercise and increased energy expenditure; (3) increased muscle soreness; and (4) reduced muscle glycogen. If endurance training quality is consistently compromised during the course of a specific concurrent training program, optimal endurance development may be limited. Whilst the link between acute responses of training and subsequent training adaptation has not been fully established, there is some evidence suggesting that cumulative effects of fatigue may contribute to limiting optimal endurance development. Thus, the current review will (1) explore cross-sectional studies that have reported impaired endurance performance following a single, or multiple bouts, of resistance training; (2) identify the potential impact of fatigue on chronic endurance development; (3) describe the implications of fatigue on the quality of endurance training sessions during concurrent training, and (4) explain the mechanisms contributing to resistance training-induced attenuation on endurance performance from neurological, biomechanical and metabolic standpoints. Increasing the awareness of resistance training-induced fatigue may encourage coaches to consider modulating concurrent training variables (e.g., order of training mode, between-mode recovery period, training intensity, etc.) to limit the carry-over effects of fatigue from resistance to endurance training sessions.

Reporting of acute programme variables and exercise descriptors in rehabilitation strength training for tibiofemoral joint soft tissue injury: A systematic review

OBJECTIVE

Strength training acute programme variables (APVs) can impact tibiofemoral joint injury outcomes. Exercise descriptors (EDs; e.g. patient-position) specify configurations within which APVs are applied. Evidence-based practice depends on adequate reporting of APVs and EDs to replicate strength training interventions in clinical practice. This systematic review assessed APV and ED reporting for adults with tibiofemoral joint injury (anterior cruciate ligament (ACL)/posterior cruciate ligament (PCL)/medial collateral ligament (MCL)/lateral collateral ligament (LCL)/meniscus/hyaline cartilage (HC)).

METHODS

PRISMA guidelines were followed. Specific key-term combinations were employed and database searches performed. Descriptive/observational/experimental studies were included (2006-2018). Studies needed to report pre-defined APVs or EDs for ≥51% of all exercises to be included. Frequency counts were made of studies adequately reporting APVs and EDs.

RESULTS

Sixteen articles were included (ACL = 13; meniscus = 3). No PCL/MCL/LCL/HC articles were identified. Of nine APVs, five and four were consistently reported by the majority of ACL (≥7) and meniscal (≥2) studies, respectively. Of eight EDs, four were consistently reported by the majority of both ACL (≥8) and meniscal (≥2) studies.

CONCLUSION

Many APVs and EDs were not adequately reported. Future studies should better document APVs and EDs for higher standards of intervention reporting and enhanced translation of research to clinical practice.

Effects of pomegranate supplementation on exercise performance and post-exercise recovery in healthy adults: a systematic review

The functional significance of pomegranate (POM) supplementation on physiological responses during and following exercise is currently unclear. This systematic review aimed (i) to evaluate the existing literature assessing the effects of POM supplementation on exercise performance and recovery; exercise-induced muscle damage, oxidative stress, inflammation; and cardiovascular function in healthy adults and (ii) to outline the experimental conditions in which POM supplementation is more or less likely to benefit exercise performance and/or recovery. Multiple electronic databases were used to search for studies examining the effects of POM intake on physiological responses during and/or following exercise in healthy adult. Articles were included in the review if they investigated the effects of an acute or chronic POM supplementation on exercise performance, recovery and/or physiological responses during or following exercise. The existing evidence suggests that POM supplementation has the potential to confer antioxidant and anti-inflammatory effects during and following exercise, to improve cardiovascular responses during exercise, and to enhance endurance and strength performance and post-exercise recovery. However, the beneficial effects of POM supplementation appeared to be less likely when (i) unilateral eccentric exercise was employed, (ii) the POM administered was not rich in polyphenols (<1·69 g/l) and (iii) insufficient time was provided between POM-ingestion and the assessment of physiological responses/performance (≤1 h). The review indicates that POM has the potential to enhance exercise performance and to expedite recovery from intensive exercise. The findings and recommendations from this review may help to optimise POM-supplementation practice in athletes and coaches to potentially improve exercise-performance and post-exercise recovery.

Effect of Branched-Chain Amino Acid Supplementation on Recovery Following Acute Eccentric Exercise

This study investigated the effect of branched-chain amino acid (BCAA) supplementation on recovery from eccentric exercise. Twenty males ingested either a BCAA supplement or placebo (PLCB) prior to and following eccentric exercise. Creatine kinase (CK), vertical jump (VJ), maximal voluntary isometric contraction (MVIC), jump squat (JS) and perceived soreness were assessed. No significant (p > 0.05) group by time interaction effects were observed for CK, soreness, MVIC, VJ, or JS. CK concentrations were elevated above baseline (p < 0.001) in both groups at 4, 24, 48 and 72 hr, while CK was lower (p = 0.02) in the BCAA group at 48 hr compared to PLCB. Soreness increased significantly from baseline (p < 0.01) in both groups at all time-points; however, BCAA supplemented individuals reported less soreness (p < 0.01) at the 48 and 72 hr time-points. MVIC force output returned to baseline levels (p > 0.05) at 24, 48 and 72 hr for BCAA individuals. No significant difference between groups (p > 0.05) was detected for VJ or JS. BCAA supplementation may mitigate muscle soreness following muscle-damaging exercise. However, when consumed with a diet consisting of ~1.2 g/kg/day protein, the attenuation of muscular performance decrements or corresponding plasma CK levels are likely negligible.