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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. [ABSTRACT FROM AUTHOR]

Introduction: Athletic training requires both challenging stimuli for adaptation and sufficient recovery for improved performance. While cold water immersion (CWI) is already a popular recovery method, handheld percussive massage (PM) devices have also gained popularity in recent years. This study aims to assess the effects of CWI and PM on performance recovery after strenuous eccentric exercises compared to a passive rest (PR) control condition. Methods: Thirty-four healthy physically active participants (9 females, 25 males) were randomly divided into three groups: CWI (n = 11), PM (n = 11), and passive rest (PR) (n = 12). They underwent an exhausting eccentric exercise protocol and different measurements at six time points (baseline, POST1, POST2, POST24, POST48, and POST72) over the time course of 72 h. These included subjective assessments of muscle soreness and perceived stiffness as well as measures of skin temperature, leg volume, creatine kinase activity, and three different jump tests. The eccentric exercise protocol consisted of 15 min downhill running (slope: 12%, speed: 10 km/h) and 3 sets of successive depth jumps (dropping height: 0.5 m) until individual exhaustion. After POST1 measurements, participants received 12 min of either CWI (11 ± 0.5°C), PM (40 Hz) or PR (supine posture). Results: No significant group effects were found for the number of depth jumps performed during the exhaustion protocol. All jump tests displayed a significant group × time interaction effect. Post-hoc analysis indicated significant lower jump heights in ΔPOST2 between CWI and both PM and PR. No other significant group effects were observed at any time point. No significant group × time interaction effects were noted for CK, leg volume, and soreness. The perceived stiffness showed a significant group × time interaction effect. Post-hoc analysis revealed a significant decrease in stiffness for PM compared to PR at ΔPOST2. Conclusion: Neither CWI nor PM showed any significant improvement in performance recovery over the 72-h period following strenuous eccentric exercise compared to PR. CWI showed an immediate performance decline which may be attributed to a cold-related reduction in motor nerve conduction velocity. [ABSTRACT FROM AUTHOR]

This study assessed whether symptoms of muscle damage could be reduced by a combination of therapeutic ultrasound and electrical stimulations, and whether this could be enhanced by blood flow restriction. Before and 48 h after performing eccentric elbow flexion exercises, individuals completed assessments of muscle damage. A 10-min therapeutic ultrasound and electrical stimulation treatment was then applied with and without blood flow restriction to assess short (5 min) and long-term (24 h) improvements. Twenty-three individuals completed the study (11 females). Data were analysed using Bayesian repeated measures ANOVAs. The damaging exercise increased discomfort (BF10 = 2.93e14) and relaxed joint angle (BF10 = 2425.90) while decreasing pain pressure threshold (BF10 = 289.71). Each of these variables was acutely improved with the combination treatment protocol (all BF10 ≥ 74) with no added effect of blood flow restriction. A combination of therapeutic ultrasound and interferential electrical stimulations appeared effective at acutely alleviating symptoms of muscle damage with no additive effect of blood flow restriction. [ABSTRACT FROM AUTHOR]

This study aimed to compare the acute inflammatory response following high-intensity eccentric exercise between resistance-trained young and master athletes with similar performance levels. Resistance-trained young (n=8; 22±2 years) and master (n=8; 52±4 years) male athletes of a similar performance level performed a standardized high-intensity eccentric squat exercise protocol (10 sets of half-squats at 70% of 1-repetition maximum). The serum concentration of 20 biomarkers related to tissue damage, inflammation, remodeling, and repair was measured at baseline, immediately after exercise, and over a 72 h recovery period. Both groups experienced similar muscle damage as evidenced by a comparable increase in creatine kinase activity 24 h after exercise (p<0.001). Interleukin-6 (p=0.009) and growth hormone (p<0.001) increased immediately post-exercise in both groups. Monocyte chemoattractant protein-1 increased immediately post-exercise only in young athletes (p=0.003) and then decreased 24 h later. There were no significant differences for the remaining variables, including cell markers related to neutrophil/macrophage activation or pro/anti-inflammatory cytokines. Resistance-trained young and master athletes, matched for performance level, showed an overall similar inflammatory response to eccentric exercise, possibly reflecting regulatory mechanisms or immunological adaptations to chronic stimulation in master athletes. [ABSTRACT FROM AUTHOR]

Objective: To investigate the effect of exogenous recombinant human Annexin A6 (rhANX A6) intervention on early plasma membrane damage and its metabolic characteristics in skeletal muscle in mice with eccentric exercise injury models. Method: Fifty-six C57 male mice, aged 8 weeks, were randomly divided into the quiet control group (group C), exercise group injected with phosphate-buffer saline (group EP) and exercise group injected with rhANX A6(group ER). The exercise groups were further subdivided based on different post- exercise sampling times: EP2, EP6, EP12, and ER2, ER6, ER12, with 8 mice in each subgroup. Two hours before exercise, the group EP and group ER received intraperitoneal injections with 1*PBS buffer (1 × concentration) and rhANX A6 (0.8 mg/kg), respectively. ELISA was used to detect the content of ANX A6 in serum creatine kinase (CK), Annexin A6 (ANX A6) and skeletal muscle in each group of mice, and Evans Blue dye (EBD) was used to observe the damage of the skeletal muscle plasma membrane of each group of mice. Result: The serum CK activity in all EP subgroups and ER12h were significantly higher than those in the C group (P<0.01). At the same time point, CK levels in all EP subgroups were significantly higher than in the ER group (P<0.05). The average fluorescence intensity of EBD- positive regions in all EP and ER subgroup was significantly higher than that in group C (P<0.01). All EP subgroups had significantly higher intensities than the ER group (P<0.01). The serum ANX A6 levels in all ER subgroups and EP6h, EP12h were significantly higher than that in group C (P<0.01). At 12h time point, ANX 46 levels in the ER group were significantly higher than in the EP group(P<0.05). ANX A6 levels in skeletal muscle of all EP and ER subgroups were significantly higher than that in group C (P<0.05); All ER subgroups had significantly higher than those in the EP group(P<0.05). Conclusion: Exogenous rhANX A6 injection 2 hours before eccentric exercise in mice can significantly improve the early plasma membrane injury in skeletal muscle after exercise. It is speculated that rhANX A6 directly involved in the repair of early plasma membrane damage in skeletal muscle induced by eccentric exercise. [ABSTRACT FROM AUTHOR]

This study compared cardiovascular and metabolic responses during concentric and eccentric stepping. Eight participants (5 m, 3f; 22 ± 2 years) performed maximal concentric and eccentric ramp incremental tests on a modified stepping ergometer. Subsequently, three randomized 15‐min constant‐power tests were performed (1) concentric stepping at 90% of the concentric lactate threshold (LT), (2) eccentric stepping at the same power, and (3) eccentric stepping at the same oxygen uptake (V̇O2). At equivalent power (36 ± 6 W, p = 0.62), eccentric stepping resulted in 46 ± 8% lower V̇O2, 16 ± 6% lower heart rate (HR), and 11 ± 5% lower mean arterial blood pressure compared to concentric (p < 0.01). Matching V̇O2 required 65 ± 19% more power during eccentric stepping (p < 0.01). During this test, eccentric V̇O2 and HR continued to increase, resulting in a 22 ± 29% higher V̇O2 and 19 ± 16% higher HR in the final minute (p < 0.001). Reduced cardiorespiratory demand during eccentric stepping at the same power as concentric demonstrates a higher eccentric power is required to produce the same V̇O2. However, despite being below the concentric LT, eccentric V̇O2 and HR continued to increase past the predicted steady state, indicating a higher exercise intensity. [ABSTRACT FROM AUTHOR]

Extracellular vesicle (EV) cargo is known to change in response to stimuli such as muscle damage. This study aimed to assess particle size, concentration and microRNA (miR) content within small EV‐enriched separations prepared from human blood taken before and after unaccustomed eccentric‐biased exercise‐induced muscle damage. Nine male volunteers underwent plyometric jumping and downhill running, with blood samples taken at baseline, 2, and 24 h post‐exercise. EVs were separated using size exclusion chromatography (SEC) and their characteristics evaluated by nanoparticle tracking. No changes in EV size or concentration were seen following the muscle‐damaging exercise. Small RNA sequencing identified 240 miRs to be consistently present within the EVs. RT‐qPCR analysis was performed: specifically, for known muscle‐enriched/important miRs, including miR‐1, −206, −133a, −133b, −31, −208b, −451a, −486 and − 499 and the immune‐important miR‐21, −146a and − 155. Notably, none of the immune‐important miRs within the EVs tested changed in response to the muscle damage. Of the muscle‐associated miRs tested, only the levels of miR‐31‐5p were seen to change with decreased levels at 24 h compared to baseline and 2 h, indicating involvement in the damage response. These findings shed light on the dynamic role of EV miRs in response to exercise‐induced muscle damage. [ABSTRACT FROM AUTHOR]

Introduction: Muscle fatigue, characterized by diminished force production and contraction sustainability, can impair muscle coordination and increase joint instability. Differing force profiles used in fatiguing tasks, such as prolonged eccentric trunk protocols, might provide insights into individualized strategies and resulting spinal stability. Thus, this study assessed individual differences in fatigue characteristics during an eccentric trunk flexion-extension protocol in a population of asymptomatic individuals. Methods: Twelve participants (2 f/10 m, 29 ± 4 years, 78.4 ± 16.9 kg, 1.76 ± 0.10 m) performed an eccentric trunk flexion and extension protocol on an isokinetic dynamometer (45° flexion to 10° extension; 60°/s), with final analysis on 8 participants for trunk flexion and 11 for trunk extension due to data exclusions. Participants engaged in a maximal all-out (AO) task for 2 min. Each participant's torque output (Nm) was assessed on a repetition-by-repetition basis, and smoothened by a moving average of 5 repetitions. Individual time profiles for reaching fatigue thresholds (10%, 15%, 20% and 30% reduction of initial torque output), and inter subject variability (by coefficient of variation, CV in %) were assessed throughout the AO task. Further, percentage torque reduction and variability were assessed at mid (1-minute) and end (2-minute) of task. Results: On average, for flexor and extensor muscles combined, participants reached a force reduction of 10% within 23.2 ± 19.1 s, of 15% within 44.9 ± 19.6 s, of 20% in 62.4 ± 26.3 s, and of 30% within 79.2 ± 21.8 s. The variability between individuals for the timepoint of reaching the defined torque thresholds was assessed by CV ranged between 23.4% and 103.8% for trunk flexor muscles, and between 28.4% and 56.5% for trunk extensor muscles. Discussion: A reduction of up to 20% was seen on average for all participants within 1-minute of eccentric trunk flexion and extension. Different inter-individual force output profiles were seen throughout the AO protocol, potentially related to physiological, skill-based, technical, adaptational, and/or motivational factors. The increase in fatigue resulted in a reduction in variability among individuals. A 2-minute protocol effectively induced pronounced fatigue, offering insights into individual force profiles and strategies. [ABSTRACT FROM AUTHOR]

Recent studies have shown that the extramuscular connective tissue (ECT) is thickened and stiffened in delayed onset muscle soreness (DOMS). However, contrarily to the normal population, severe DOMS is rare in athletes or highly trained individuals. The present randomized, controlled trial therefore aimed to investigate pain as well as microcirculation and stiffness of the ECT and the erector spinae muscle following submaximal eccentric trunk extension exercise not causing DOMS. The effect of manual treatment by a therapist (myofascial release; MFR) on these parameters was to be studied. Trained healthy participants (n = 21; 31.3 ± 9.6 years; > 4 h exercise per week) performed submaximal eccentric exercise of the trunk extensors. One group was manually treated (n = 11), while the other group (n = 10) received placebo treatment with sham laser therapy. Stiffness of the ECT and the erector spinae muscle (shear wave elastography), microcirculation (white light and laser Doppler spectroscopy), palpation pain (100 mm visual analogue scale, VAS) and pressure pain threshold (indentometry, PPT) were assessed before (t0), 24 h (t24) and 48 h (t48) after conditions. Erector spinae muscle stiffness increased after eccentric exercise from t0 to t24 (0.875 m/s) and from t0 to t48 (0.869 m/s). After MFR, erector spinae muscle stiffness decreased in contrast to placebo treatment at t24 (-0.66 m/s), while ECT stiffness remained unchanged. Oxygen saturation increased (17 - 20.93%) and relative haemoglobin decreased (-9.1 - -12.76 AU) after eccentric exercise and MFR differed from placebo treatment at t48 (-3.71 AU). PPT differed after MFR from placebo treatment at t48 (20.69 N/mm), while VAS remained unchanged. Multiple linear regression showed that ECT stiffness and group membership predicted erector spinae muscle stiffness. MFR could have a positive effect on pain, microcirculation and muscle stiffness after submaximal eccentric exercise, suggesting better recovery, which needs to be confirmed by future work. [ABSTRACT FROM AUTHOR]

Introduction: The effect of eccentric exercise--induced muscle damage (EIMD) on cycling efficiency is unknown. The aim of the present study was to assess the effect of EIMD on gross and delta efficiency and the cardiopulmonary responses to cycle ergometry. Methods: Twenty-one recreational athletes performed cycling at 70%, 90%, and 110% of the gas exchange threshold (GET) under control conditions (Control) and 24 h following an eccentric damaging protocol (Damage). Knee extensor isometric maximal voluntary contraction, potentiated twitch (Qtw,pot), and voluntary activation were assessed before Control and Damage. Gross and delta efficiency were assessed using indirect calorimetry, and cardiopulmonary responses were measured at each power output. Electromyography root-mean-square (EMGRMS) during cycling was also determined. Results: Maximal voluntary contraction was 25%± 18%lower for Damage than Control (P < 0.001). Gross efficiency was lower for Damage than Control (P < 0.001) by 0.55% ± 0.79%, 0.59% ± 0.73%, and 0.60% ± 0.87% for 70%, 90%, and 110% GET, respectively. Delta efficiency was unchanged between conditions (P = 0.513). Concurrently, cycling EMGRMS was higher for Damage than Control (P = 0.004). An intensity-dependent increase in breath frequency and ... was found, which were higher for Damage only at 110% GET (P ≤ 0.019). Conclusions: Thus, gross efficiency is reduced following EIMD. The concurrently higher EMGRMS suggests that increases in muscle activation in the presence of EIMD might have contributed to reduced gross efficiency. The lack of change in delta efficiency might relate to its poor reliability hindering the ability to detect change. The findings also show that EIMD-associated hyperventilation is dependent on exercise intensity, which might relate to increases in central command with EIMD. [ABSTRACT FROM AUTHOR]

Purpose: Exercise-induced muscle damage (EIMD) results in the generation of reactive oxygen species (ROS), but little is known about the temporal profile of change in ROS post-EIMD and how ROS levels relate to the onset of and recovery from EIMD. Our primary aim was to examine the effect of EIMD on the pattern of change in the blood level of thiol-oxidised albumin, a marker of oxidative stress. Methods: Seven male participants were subjected on separate days to eccentric muscle contraction to cause EIMD or a no-exercise condition. After each session, the participants collected daily dried blood spots to measure thiol-oxidised albumin and returned to the laboratory every 2 days for the assessment of indirect markers of EIMD, namely maximal voluntary contraction (MVC), delayed onset muscle soreness (DOMS), creatine kinase (CK), and myoglobin. Results: Eccentric exercise resulted in a significant decrease in MVC and increase in DOMS, CK, myoglobin, and thiol-oxidised albumin with the latter reaching above baseline level within 24–48 h post-exercise. All the markers of EIMD returned to baseline level within 6 days post-exercise, but not the level of thiol-oxidised albumin which remained elevated for 10 days after exercise. There was a moderate correlation between changes in thiol-oxidised albumin and DOMS, but no significant relationship between any other markers of muscle damage. Conclusion: The levels of thiol-oxidised albumin increase in response to EIMD and remain elevated for several days post-exercise. The temporal pattern of change in the level of thiol-oxidised albumin suggests that this may be a useful biomarker of muscle repair post-EIMD. [ABSTRACT FROM AUTHOR]

Purpose: Eccentric strength training is an innovative and promising approach to improve exercise performance. However, most eccentric training studies in the past were performed with a focus on the lower extremities. The present study aimed to test the feasibility and effects on strength and power adaptations of a structured upper-body eccentric training program. Methods: Fourteen (median age (Q1–Q3) 29 years (27–32); 9 females, 5 males) healthy, regularly exercising individuals performed 20 progressive training sessions (2–3 sessions/week at 20–50% peak power for 8–14 min) on a symmetric eccentric arm-crank ergometer. Before and after the intervention, anaerobic peak power (PP) and maximal concentric aerobic power output (POmax) on an arm-crank ergometer as well as the one repetition maximum (1RM) for bench press were determined as main outcome parameters. A p-value ≤ 0.05 was considered statistically significant. Results: Significant improvements in PP (+ 4% (1–8), p = 0.007), POmax (+ 6% (0–8); p = 0.01), and 1RM (+ 12% (10–17); p < 0.001) were found. Exercise intensity was relatively low at 64% (55–70) of maximum heart rate. Conclusions: Twenty progressive training sessions on a symmetric arm-crank ergometer are effective in inducing significant aerobic and anaerobic performance and strength improvements in the upper body. This intervention is safe and feasible, and can be performed at relatively low cardiovascular intensities. Therefore, this training method offers an interesting approach from elite sports to rehabilitation. [ABSTRACT FROM AUTHOR]

Eccentric upper‐body exercise performed 24 h prior to high‐altitude decompression has previously been shown to aggravate venous gas emboli (VGE) load. Yet, it is unclear whether increasing the muscle mass recruited (i.e., upper vs. whole‐body) during eccentric exercise would exacerbate the decompression strain. Accordingly, this study aimed to investigate whether the total muscle mass recruited during eccentric exercise influences the decompression strain. Eleven male participants were exposed to a simulated altitude of 24,000 ft for 90 min on three separate occasions. Twenty‐four hours before each exposure, participants performed one of the following protocols: (i) eccentric whole‐body exercise (ECCw; squats and arm‐cycling exercise), (ii) eccentric upper‐body exercise (ECCu; arm‐cycling), or (iii) no exercise (control). Delayed onset muscle soreness (DOMS) and isometric strength were evaluated before and after each exercise intervention. VGE load was evaluated at rest and after knee‐ and arm‐flex provocations using the 6‐graded Eftedal–Brubakk scale. Knee extensor (−20 ± 14%, P = 0.001) but not elbow flexor (−12 ± 18%, P = 0.152) isometric strength was reduced 24 h after ECCw. ECCu reduced elbow flexor isometric strength at 24 h post‐exercise (−18 ± 10%, P < 0.001). Elbow flexor DOMS was higher in the ECCu (median 6) compared with ECCw (5, P = 0.035). VGE scores were higher following arm‐flex provocations in the ECCu (median (range), 3 (0–4)) compared with ECCw (2 (0–3), P = 0.039) and control (0 (0–2), P = 0.011), and in ECCw compared with control (P = 0.023). VGE were detected earlier in ECCu (13 ± 20 min) compared with control (60 ± 38 min, P = 0.021), while no differences were noted between ECCw (18 ± 30 min) and control or ECCu. Eccentric exercise increased the decompression strain compared with control. The VGE load varied depending on the body region but not the total muscle mass recruited. Highlights: What is the central question of this study?Does exercise‐induced muscle damage (EIMD) resulting from eccentric exercise influence the presence of venous gas emboli (VGE) during a 90 min continuous exposure at 24,000 ft?What is the main finding and its importance?EIMD led to an earlier manifestation and greater VGE load compared with control. However, the decompression strain was dependent on the body region but not the total muscle mass recruited. [ABSTRACT FROM AUTHOR]

Abstract Eccentric upper‐body exercise performed 24 h prior to high‐altitude decompression has previously been shown to aggravate venous gas emboli (VGE) load. Yet, it is unclear whether increasing the muscle mass recruited (i.e., upper vs. whole‐body) during eccentric exercise would exacerbate the decompression strain. Accordingly, this study aimed to investigate whether the total muscle mass recruited during eccentric exercise influences the decompression strain. Eleven male participants were exposed to a simulated altitude of 24,000 ft for 90 min on three separate occasions. Twenty‐four hours before each exposure, participants performed one of the following protocols: (i) eccentric whole‐body exercise (ECCw; squats and arm‐cycling exercise), (ii) eccentric upper‐body exercise (ECCu; arm‐cycling), or (iii) no exercise (control). Delayed onset muscle soreness (DOMS) and isometric strength were evaluated before and after each exercise intervention. VGE load was evaluated at rest and after knee‐ and arm‐flex provocations using the 6‐graded Eftedal–Brubakk scale. Knee extensor (−20 ± 14%, P = 0.001) but not elbow flexor (−12 ± 18%, P = 0.152) isometric strength was reduced 24 h after ECCw. ECCu reduced elbow flexor isometric strength at 24 h post‐exercise (−18 ± 10%, P

Abstract A significant increase in circulating cell‐free DNA (cfDNA) occurs with physical exercise, which depends on the type of exertion and the duration. The aims of this study were as follows: (1) to investigate the time course of cfDNA and conventional markers of muscle damage from immediately after to 96 h after muscle‐damaging exercise; and (2) to investigate the relationship between cfDNA and indicators of primary (low‐frequency fatigue and maximal voluntary isometric contraction) and secondary (creatine kinase and delayed‐onset muscle soreness) muscle damage in young healthy males. Fourteen participants (age, 22 ± 2 years; weight, 84.4 ± 11.2 kg; height, 184.0 ± 7.4 cm) performed 50 intermittent drop jumps at 20 s intervals. We measured cfDNA and creatine kinase concentrations, maximal voluntary isometric contraction torque, low‐frequency fatigue and delayed‐onset muscle soreness before and at several time points up to 96 h after exercise. Plasma cfDNA levels increased from immediately postexercise until 72 h postexercise (P

Abstract A noninvasive, immediate, and convenient method for assessing muscle tissue status during exercise-induced muscle damage (EIMD) has not been established. This study was designed to assess and determine parameters suitable for measuring EIMD after eccentric exercise, using multi-frequency bioimpedance analysis (BIA). Thirty-five young male participants performed dumbbell exercises with their left arm, and their BIA parameters were measured at various time points up to 168 h post exercise using a multi-frequency BIA device. At all-time points, intra and extracellular water content was greater in the left arm than in the right arm, whereas the impedance, reactance, resistance, and phase angle were lower in the left arm than in the right arm. Established EIMD indices, such as maximal isometric voluntary contraction, were measured and used in correlational analyses. Only reactance was correlated with biomarkers, indicating muscle damage (r = − 0.56 to − 0.49). Furthermore, reactance was found to correlate well with indirect indicators of EIMD, suggesting that it may be a suitable marker for evaluating EIMD. However, the relationship with the limited evaluation indices employed in this study is constrained. Future studies should investigate the correlation between reactance and direct damage indicators, such as structural damage, observed in biopsies.

A significant increase in circulating cell‐free DNA (cfDNA) occurs with physical exercise, which depends on the type of exertion and the duration. The aims of this study were as follows: (1) to investigate the time course of cfDNA and conventional markers of muscle damage from immediately after to 96 h after muscle‐damaging exercise; and (2) to investigate the relationship between cfDNA and indicators of primary (low‐frequency fatigue and maximal voluntary isometric contraction) and secondary (creatine kinase and delayed‐onset muscle soreness) muscle damage in young healthy males. Fourteen participants (age, 22 ± 2 years; weight, 84.4 ± 11.2 kg; height, 184.0 ± 7.4 cm) performed 50 intermittent drop jumps at 20 s intervals. We measured cfDNA and creatine kinase concentrations, maximal voluntary isometric contraction torque, low‐frequency fatigue and delayed‐onset muscle soreness before and at several time points up to 96 h after exercise. Plasma cfDNA levels increased from immediately postexercise until 72 h postexercise (P < 0.01). Elevation of postexercise cfDNA was correlated with both more pronounced low‐frequency fatigue (r = −0.52, P = 3.4 × 10−11) and delayed‐onset muscle soreness (r = 0.32, P = 0.00019). Levels of cfDNA change in response to severe primary and secondary muscle damage after exercise. Levels of cfDNA exhibit a stronger correlation with variables related to primary muscle damage than to secondary muscle damage, suggesting that cfDNA is a more sensitive marker of acute loss of muscle function than of secondary inflammation or damaged muscle fibres. What is the central question of this study?How do plasma cell‐free DNA (cfDNA) levels change in response to primary and secondary muscle damage when muscle‐damaging exercise is performed without metabolic stress?What is the main finding and its importance?In this study, we found that cfDNA concentration increases following severe primary and secondary muscle damage after 50 drop jumps. However, acute postexercise increases in cfDNA were higher than following secondary muscle damage and were more correlated with variables related to primary muscle damage (low‐frequency fatigue). This suggests that muscle‐damaging exercise causing no accumulation of metabolites can lead to acute and delayed increases in cfDNA levels. However, they are more sensitive to primary muscle damage. [ABSTRACT FROM AUTHOR]

A noninvasive, immediate, and convenient method for assessing muscle tissue status during exercise-induced muscle damage (EIMD) has not been established. This study was designed to assess and determine parameters suitable for measuring EIMD after eccentric exercise, using multi-frequency bioimpedance analysis (BIA). Thirty-five young male participants performed dumbbell exercises with their left arm, and their BIA parameters were measured at various time points up to 168 h post exercise using a multi-frequency BIA device. At all-time points, intra and extracellular water content was greater in the left arm than in the right arm, whereas the impedance, reactance, resistance, and phase angle were lower in the left arm than in the right arm. Established EIMD indices, such as maximal isometric voluntary contraction, were measured and used in correlational analyses. Only reactance was correlated with biomarkers, indicating muscle damage (r = − 0.56 to − 0.49). Furthermore, reactance was found to correlate well with indirect indicators of EIMD, suggesting that it may be a suitable marker for evaluating EIMD. However, the relationship with the limited evaluation indices employed in this study is constrained. Future studies should investigate the correlation between reactance and direct damage indicators, such as structural damage, observed in biopsies. [ABSTRACT FROM AUTHOR]

Nordic Hamstring Exercise (NHE) is one of the best exercises proposed for injury prevention of hamstring muscles. However, its effects on lower extremity proprioception are unclear. The aim of this study was to investigate the immediate effects of a single bout of NHE on hip and knee joints' proprioception. Forty collegiate male soccer players participated in this study with a mean age of 22.85 ± 1.82 years and were randomized into either control (n = 20) or experimental (n = 20) groups. Each subject participated in pre-test measurements in which hip and knee active joints position sense (JPS) were assessed in standing and lying tasks using the image-capturing method. The experimental group then performed three sets of NHE with 10 repetitions in each set, while the control group rested for 10 min. Paired and independent t-tests were used for calculating the differences within and between groups on SPSS software, respectively. The level of significance was P ≤ 0.05. Hip JPS in the lying task and knee JPS in both of the standing and lying tasks were impaired significantly after performing a single bout of NHE (P ≤ 0.05). However, the effects of this exercise on hip JPS in the standing task were not significant (P ≥ 0.05). NHE performing with three sets of 10 repetitions can significantly impair hip and knee JPS immediately after exercise and reduce the proprioception acuity of the lower limbs. It is recommended to perform this exercise at a time rather than before training or match sessions. [ABSTRACT FROM AUTHOR]

BACKGROUND: Collagen is the most abundant extracellular matrix component, which is closely related to the structure and function of the extracellular matrix of skeletal muscle, but the effect and mechanism of recombinant human collagen (rhC) produced by bioengineering technology on the extracellular matrix of skeletal muscle are unclear. OBJECTIVE: To investigate the effect of rhC supplementation on the remodeling of skeletal muscle extracellular matrix after eccentric exercise, thereby revealing the possible mechanism by which rhC improves the injury of skeletal muscle extracellular matrix and promote the recovery after exercise. METHODS: A total of 104 healthy male C57 mice aged 8 weeks old were randomly divided into control group (normal saline), low-dose rhC group (0.2 g/kg), medium-dose rhC group (1.0 g/kg), and high-dose rhC group (2.0 g/kg). Two mice in each group were selected after continuous 7 days of intragastric intervention, and organs were dissected for hematoxylin-eosin staining to determine inflammatory infiltrates. On the 8th day, the remaining mice were subjected to eccentric exercise. The structural changes of the skeletal muscle extracellular matrix were observed under scanning electron microscopy immediately (0), 24, 48, and 96 hours after eccentric exercise. Meanwhile, grip strength, creatine kinase activity, and protein levels of matrix metalloproteinases 2, 9, 14 and tissue inhibitor of metalloproteinase-2 in skeletal muscle were detected by western blot assay. RESULTS AND CONCLUSION: Hematoxylin-eosin staining results indicated that short-term rhC supplementation showed no significant effects on the morphology of the heart, liver, spleen and kidney. After one-time eccentric exercise, the recovery rate of grip strength in the medium- and high-dose rhC groups was significantly increased (P < 0.01). The trend of creatine kinase changes was consistent in all groups and there was no significant difference between groups. The recovery process of the extracellular matrix in the low-dose rhC group was faster than that in the control group, and the muscle tract membrane in the medium- and high-dose rhC groups was more complete. The protein level of matrix metalloproteinase 9 in the high-dose rhC group was significantly decreased (P < 0.05). The protein levels of matrix metalloproteinase 14 in the medium- and high-dose rhC groups were significantly decreased (P < 0.05). The protein levels of matrix metalloproteinase 2 in the medium- and high-dose rhC groups were significantly decreased (P < 0.05). Tissue inhibitor of metalloproteinase-2 protein levels in the medium- and high-dose rhC groups were significantly increased (P < 0.05). The ratio of matrix metalloproteinase 2 to tissue inhibitor of metalloproteinase-2 in each rhC group was significantly decreased (P < 0.05). To conclude, pre-supplementation of 1.0 and 2.0 g/kg rhC for 7 days can inhibit extracellular matrix degradation in skeletal muscle after exercise by modulating matrix metalloproteinases and matrix metalloproteinase inhibitors, thereby promoting recovery of skeletal muscle strength in mice. [ABSTRACT FROM AUTHOR]

This study examined the effect of repeated bouts of level and downhill running on physiological markers of effort and exercise-induced muscle soreness in trained female distance runners. Ten participants (Age: 24.4 ± 2.0 years; V̇O2peak: 52.9 ± 1.1 mL·kg−1·min−1), naïve to downhill running, completed six alternate 5 min trials of level and downhill running (−15%) at a 70% velocity at V̇O2peak on two occasions, three weeks apart. Perceived muscle soreness was measured upon completion and in the 72 h post exercise. V̇O2, Heart Rate (HR), Blood Lactate (BLa), and Respiratory Exchange Ratio (RER) were lower running downhill (p < 0.016, ηp2 > 0.541). For the first downhill run, Rating of Perceived Exertion (RPE) was higher compared to that for level running (p = 0.051; d = 0.447), but for the remaining trials, RPE was lower when running downhill (p < 0.004; d > 0.745). V̇O2, HR, and RER were not different in the second bout (p > 0.070, ηp2 < 0.318); however, V̇O2 was lower in each downhill trial (Δ = 1.6–2.2 mL·kg−1·min−1; d = 0.382–0.426). In the second bout, BLa was lower (p = 0.005, ηp2 = 0.602), RPE in the first trial was lower (p = 0.002; d = 0.923), and post exercise perceived soreness of the gastrocnemius, quadriceps, and hamstrings was attenuated (p < 0.002; ηp2 > 0.693). Perceived soreness of the gluteal muscles was lower in the second bout immediately post exercise, 24 h, and 48 h post exercise (p < 0.025; d > 0.922). A repeated bout of downhill running attenuated perceived muscle soreness and may modulate the physiological and perceived physical demand of a second bout of level and downhill running. [ABSTRACT FROM AUTHOR]

Copyright of Revija Šport is the property of Sport: Revija Za Teoreticna in Praticna Vprasanja Sporta and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract This study compared cardiovascular and metabolic responses during concentric and eccentric stepping. Eight participants (5 m, 3f; 22 ± 2 years) performed maximal concentric and eccentric ramp incremental tests on a modified stepping ergometer. Subsequently, three randomized 15‐min constant‐power tests were performed (1) concentric stepping at 90% of the concentric lactate threshold (LT), (2) eccentric stepping at the same power, and (3) eccentric stepping at the same oxygen uptake (V̇O2). At equivalent power (36 ± 6 W, p = 0.62), eccentric stepping resulted in 46 ± 8% lower V̇O2, 16 ± 6% lower heart rate (HR), and 11 ± 5% lower mean arterial blood pressure compared to concentric (p

IntroductionAthletic training requires both challenging stimuli for adaptation and sufficient recovery for improved performance. While cold water immersion (CWI) is already a popular recovery method, handheld percussive massage (PM) devices have also gained popularity in recent years. This study aims to assess the effects of CWI and PM on performance recovery after strenuous eccentric exercises compared to a passive rest (PR) control condition.MethodsThirty-four healthy physically active participants (9 females, 25 males) were randomly divided into three groups: CWI (n = 11), PM (n = 11), and passive rest (PR) (n = 12). They underwent an exhausting eccentric exercise protocol and different measurements at six time points (baseline, POST1, POST2, POST24, POST48, and POST72) over the time course of 72 h. These included subjective assessments of muscle soreness and perceived stiffness as well as measures of skin temperature, leg volume, creatine kinase activity, and three different jump tests. The eccentric exercise protocol consisted of 15 min downhill running (slope: 12%, speed: 10 km/h) and 3 sets of successive depth jumps (dropping height: 0.5 m) until individual exhaustion. After POST1 measurements, participants received 12 min of either CWI (11 ± 0.5°C), PM (40 Hz) or PR (supine posture).ResultsNo significant group effects were found for the number of depth jumps performed during the exhaustion protocol. All jump tests displayed a significant group × time interaction effect. Post-hoc analysis indicated significant lower jump heights in ΔPOST2 between CWI and both PM and PR. No other significant group effects were observed at any time point. No significant group × time interaction effects were noted for CK, leg volume, and soreness. The perceived stiffness showed a significant group × time interaction effect. Post-hoc analysis revealed a significant decrease in stiffness for PM compared to PR at ΔPOST2.ConclusionNeither CWI nor PM showed any significant improvement in performance recovery over the 72-h period following strenuous eccentric exercise compared to PR. CWI showed an immediate performance decline which may be attributed to a cold-related reduction in motor nerve conduction velocity.

Abstract Extracellular vesicle (EV) cargo is known to change in response to stimuli such as muscle damage. This study aimed to assess particle size, concentration and microRNA (miR) content within small EV‐enriched separations prepared from human blood taken before and after unaccustomed eccentric‐biased exercise‐induced muscle damage. Nine male volunteers underwent plyometric jumping and downhill running, with blood samples taken at baseline, 2, and 24 h post‐exercise. EVs were separated using size exclusion chromatography (SEC) and their characteristics evaluated by nanoparticle tracking. No changes in EV size or concentration were seen following the muscle‐damaging exercise. Small RNA sequencing identified 240 miRs to be consistently present within the EVs. RT‐qPCR analysis was performed: specifically, for known muscle‐enriched/important miRs, including miR‐1, −206, −133a, −133b, −31, −208b, −451a, −486 and − 499 and the immune‐important miR‐21, −146a and − 155. Notably, none of the immune‐important miRs within the EVs tested changed in response to the muscle damage. Of the muscle‐associated miRs tested, only the levels of miR‐31‐5p were seen to change with decreased levels at 24 h compared to baseline and 2 h, indicating involvement in the damage response. These findings shed light on the dynamic role of EV miRs in response to exercise‐induced muscle damage.

The aim of this study was to determine whether the inclusion of a very low volume (1 set of 3 maximal repetitions) of eccentric-biased Nordic hamstring program of 21 weeks induced an increase in maximal eccentric strength and whether its magnitude was influenced by the compliance rate. The secondary aim of this study was to determine whether this eccentric-biased Nordic hamstring program was effective at reducing hamstring injury rate. Twenty-three professional soccer players formed the experimental group and undertook regular in-season hamstring strength training and monitoring for 21 weeks. Data from 23 players in the immediately preceding cohort (previous year) were included as a control group. The subdivision of the experimental group revealed that the high compliance subgroup (-13 d between sessions) exhibited higher changes in maximal eccentric strength compared with the low compliance group (-24 d between sessions; +26.5%; 95% confidence interval, 7.1%-45.9%; P < .001; g = 1.2). Five hamstring injuries (22%) were recorded in the experimental group and 9 (39%) in the control group, corresponding to a nonsignificant 2.7-fold lower risk (P = .12) of suffering hamstring injury in the experimental group. The current study demonstrates that the inclusion of a very low volume of eccentric-biased Nordic hamstring program for 21 weeks induced an increase in maximal eccentric strength (-15%) in professional soccer players, the magnitude of which depended on the players' compliance. We also found that this program was efficient (2.7-fold lower risk), although nonsignificant, at reducing hamstring injury rate in professional soccer players. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

(1) Background: This study compared the effects of mouth rinsing with a carbohydrate trial (CMR) and a placebo trial (PL) on concentric and eccentric contraction strength in multi-joint resistance exercise performance. (2) Methods: Twenty healthy adult men (age: 22.4 ± 3.7 years, body mass index: 26 ± 3.8, peak power: 378.3 ± 138.7 W) were recruited in this study. Participants were employed in a double-blind, randomized crossover design to divide participants into carbohydrate mouth rinsing trial (CMR) and placebo trial (PL). After warming up, participants used 6.6% maltodextrin (CMR) or mineral water (PL) to rinse their mouth for 20 s. Next, the participants underwent tests of maximum inertial Romanian deadlift resistance exercise comprising five sets of six reps, with 3 min rests between sets. After deducting the first repetition of each set, the mean values from the five sets were analyzed. (3) Results: The concentric peak power of the CMR trial was significantly higher than that of the PL trial (p = 0.001, Cohen's d = 0.46), the eccentric peak power of the CMR trial was significantly higher than that of the PL trial (p = 0.008, Cohen's d = 0.56), and the total work of the CMR trial was significantly higher than that of PL trial (p = 0.002, Cohen's d = 0.51). (4) Conclusions: These findings demonstrate that mouth rinsing with carbohydrates before exercise can improve concentric and eccentric contraction strength in multi-joint resistance exercise performance. [ABSTRACT FROM AUTHOR]

Despite the known beneficial effects of creatine in treating exercise-induced muscle damage (EIMD), its effectiveness remains unclear. This study investigates the recovery effect of creatine monohydrate (CrM) on EIMD. Twenty healthy men (21–36 years) were subjected to stratified, randomized, double-blind assignments. The creatine (CRE) and placebo (PLA) groups ingested creatine and crystalline cellulose, respectively, for 28 days. They subsequently performed dumbbell exercises while emphasizing eccentric contraction of the elbow flexors. The EIMD was evaluated before and after exercise. The range of motion was significantly higher in the CRE group than in the PLA group 24 h (h) post exercise. A similar difference was detected in maximum voluntary contraction at 0, 48, 96, and 168 h post exercise (p = 0.017–0.047). The upper arm circumference was significantly lower in the CRE group than in the PLA group at 48, 72, 96, and 168 h post exercise (p = 0.002–0.030). Similar variation was observed in the shear modulus of the biceps brachii muscle at 96 and 168 h post exercise (p = 0.003–0.021) and in muscle fatigue at 0 and 168 h post exercise (p = 0.012–0.032). These findings demonstrate CrM-mediated accelerated recovery from EIMD, suggesting that CrM is an effective supplement for EIMD recovery. [ABSTRACT FROM AUTHOR]

Delayed onset muscle soreness (DOMS) of the lower back is considered a surrogate for acute low back pain (aLBP) in experimental studies. Of note, it is often unquestioningly assumed to be muscle pain. To date, there has not been a study analyzing lumbar DOMS in terms of its pain origin, which was the aim of this study. Sixteen healthy individuals (L-DOMS) were enrolled for the present study and matched to participants from a previous study (n = 16, L-PAIN) who had undergone selective electrical stimulation of the thoracolumbar fascia and the multifidus muscle. DOMS was induced in the lower back of the L-DOMS group using eccentric trunk extensions performed until exhaustion. On subsequent days, pain on palpation (100-mm analogue scale), pressure pain threshold (PPT), and the Pain Sensation Scale (SES) were used to examine the sensory characteristics of DOMS. Pain on palpation showed a significant increase 24 and 48 h after eccentric training, whereas PPT was not affected (p > 0.05). Factor analysis of L-DOMS and L-PAIN sensory descriptors (SES) yielded a stable three-factor solution distinguishing superficial thermal ("heat pain ") from superficial mechanical pain ("sharp pain") and "deep pain." "Heat pain " and "deep pain" in L-DOMS were almost identical to sensory descriptors from electrical stimulation of fascial tissue (L-PAIN, all p > 0.679) but significantly different from muscle pain (all p < 0.029). The differences in sensory description patterns as well as in PPT and self-reported DOMS for palpation pain scores suggest that DOMS has a fascial rather than a muscular origin. [ABSTRACT FROM AUTHOR]

Incorporating plyometric exercises (PE) into soccer players' conditioning routines is vital for boosting their performance. Nevertheless, the effects of PE sessions with diverse volume loads on inflammation, oxidative stress, and muscle damage are not yet clearly understood. This study aimed to examine the effects of altering the volume-loads of PE on indicators of oxidative muscle damage and inflammation. The study involved forty young male soccer players who were randomly assigned to three different volume-loads of PE (Low volume-load [100 jumps]: LVL, n = 10; Moderate volume-load [150 jumps]: MVL, n = 10; and High volume-load [200 jumps]: HVL, n = 10) and a control group (CON = 10). The levels of various biomarkers including delayed onset muscle soreness (DOMS), serum lactate dehydrogenase (LDH), creatine kinase (CK), 8-hydroxy-2-deoxyguanosine (8-OHdG), malondialdehyde (MDA), protein carbonyl (PC), leukocytes, neutrophils, interleukin-6 (IL-6), and C-reactive protein (CRP) were measured at different time points. These measurements were taken at rest, immediately after completion of PE, and 24-, 48-, and 72-hours post-PE. The CK, LDH, DOMS, 8-OHdG, MDA, and PC levels were significantly increased (p < 0.05) after the PE protocol, reaching their peak values between 24 to 48 hours post-PE for all the volume-loaded groups. The levels of leukocytes, neutrophils, and IL-6 also increased after the PE session but returned to resting values within 24 hours post-PE. On the other hand, CRP levels increased at 24 hours post-PE for all the treatment groups (p < 0.05). The changes observed in the indicators of muscle damage and inflammation in response to different volume-loads of PE was not significant. However, the HVL and MVL indicated significant differences compared to LVL in the 8-OHdG (at 48-hour) and MDA (at 72-hour). Athletes engaging in higher volume-loads demonstrated more pronounced responses in terms of biochemical variables (specifically, LVL < MVL < HVL); however, these changes were not statistically significant (except 8-OHdG and MDA). [ABSTRACT FROM AUTHOR]

Background Previous research has reported that people with Joint Hypermobility Syndrome (JHS) and Ehlers-Danlos Syndrome (EDS) generally experience a high rate of muscular injury and pain. However, there is limited research comparing the recovery times and length of Delayed Onset Muscle Soreness (DOMS) in individuals with JHS to non-hypermobile individuals in response to exercise. Hypotheses/Purpose The purpose of this study was to investigate JHS and its effects on DOMS and its recovery time. Study Design Quasi-experimental, observational comparison Methods Two groups including a hypermobile group (score >4 on Beighton Scale) and a non-hypermobile group all took part in five-second long standing eccentric bicep curls based using their one- repetition maximum (1-RM) of their dominant arm to failure in order to induce DOMS. Visual analog pain scale (VAS), McGill pain scale, resting arm angle, girth, and the pressure pain threshold, all domains of DOMS, were measured over a five-day period. Results were analyzed using ANOVA with time as the repeated factor. Results Both groups experienced DOMS following the eccentric exercise. However, VAS reporting was significantly greater in the hypermobile group compared to the non-hypermobile group and there was a significant difference over time. However, other variables did not reveal any other significant findings between groups. Conclusion Individuals with JHS may experience greater DOMS and require more time to recover between treatment sessions. Therapists need to be aware that patients with hypermobility may experience higher pain levels related to exercise, and they need to adjust treatment parameters appropriately. Level of Evidence 2b [ABSTRACT FROM AUTHOR]

IntroductionMuscle fatigue, characterized by diminished force production and contraction sustainability, can impair muscle coordination and increase joint instability. Differing force profiles used in fatiguing tasks, such as prolonged eccentric trunk protocols, might provide insights into individualized strategies and resulting spinal stability. Thus, this study assessed individual differences in fatigue characteristics during an eccentric trunk flexion-extension protocol in a population of asymptomatic individuals.MethodsTwelve participants (2 f/10 m, 29 ± 4 years, 78.4 ± 16.9 kg, 1.76 ± 0.10 m) performed an eccentric trunk flexion and extension protocol on an isokinetic dynamometer (45° flexion to 10° extension; 60°/s), with final analysis on 8 participants for trunk flexion and 11 for trunk extension due to data exclusions. Participants engaged in a maximal all-out (AO) task for 2 min. Each participant's torque output (Nm) was assessed on a repetition-by-repetition basis, and smoothened by a moving average of 5 repetitions. Individual time profiles for reaching fatigue thresholds (10%, 15%, 20% and 30% reduction of initial torque output), and inter subject variability (by coefficient of variation, CV in %) were assessed throughout the AO task. Further, percentage torque reduction and variability were assessed at mid (1-minute) and end (2-minute) of task.ResultsOn average, for flexor and extensor muscles combined, participants reached a force reduction of 10% within 23.2 ± 19.1 s, of 15% within 44.9 ± 19.6 s, of 20% in 62.4 ± 26.3 s, and of 30% within 79.2 ± 21.8 s. The variability between individuals for the timepoint of reaching the defined torque thresholds was assessed by CV ranged between 23.4% and 103.8% for trunk flexor muscles, and between 28.4% and 56.5% for trunk extensor muscles.DiscussionA reduction of up to 20% was seen on average for all participants within 1-minute of eccentric trunk flexion and extension. Different inter-individual force output profiles were seen throughout the AO protocol, potentially related to physiological, skill-based, technical, adaptational, and/or motivational factors. The increase in fatigue resulted in a reduction in variability among individuals. A 2-minute protocol effectively induced pronounced fatigue, offering insights into individual force profiles and strategies.

Abstract The objective of this systematic review and meta-analysis was to investigate whether the administration of branched-chain amino acids (BCAAs) reduces exercise-induced muscle damage (EIMD) markers following eccentric exercise (EE) compared to a placebo (PL). The Cochrane bias risk tool and NutriGrade scale were used to critically evaluate the included studies. Forest plots were used to visualize the standardized mean differences (SMD) and p-values. The included studies were randomized controlled trials with either a placebo or crossover randomized design. The assessment of EIMD markers was compared between the intervention (BCAA) and placebo situations at 0, 24, 48, 72, and 96 hours after the EE protocol. Subgroup analyses were conducted to assess the effects of BCAA intake on creatine kinase concentration based on follow-up times (immediately, 24 hours, 48 hours, 72 hours, 96 hours), dosage (≥ 10 g/day, < 10 g/day), administration duration (≥ 1 week, < 1 week), exercise type (aerobic, anaerobic), and training status (trained, untrained). The intervention situation showed a significant reduction in indirect markers of EIMD compared to the placebo situation (p = 0.001; I2 = 81%). Subgroup analyses indicated that BCAA administration had a significant reducing effect on creatine kinase levels in trials with a dosage of ≥ 10 g/day, anaerobic exercise, trained individuals, and an ingestion duration of less than 1 week. The findings of this study suggest that BCAA administration reduces EIMD markers following chronic EE in both trained and untrained individuals. BCAA administration reduces creatine kinase activity at 48 hours, 72 hours, and overall post-EE compared to a placebo.

Abstract Introduction The main generator of delayed onset muscle soreness (DOMS) is still unknown. This study aimed to clarify the main generator of DOMS. Methods Twelve participants performed eccentric exercise (EE) on lower legs. MRI and ultrasound were used to assess changes of calf muscle and deep fascia before and after EE. These results were then compared to the muscle pain level. Results Compared to baseline, muscle pain peaked at 24–48 h after EE (downstairs 22.25 ± 6.196, 57.917 ± 9.298, F = 291.168, p

This study investigated the effect of different amounts of Branched-Chain Amino Acids (BCAA) supplementation on recovery from eccentric exercise. Nine healthy male subjects undertook 4 trials in a randomized crossover design. Participants ingested either a three different amount (2g, 10g, and 20g) of BCAA supplement or placebo before the eccentric exercise. Muscle pain, hunger, vertical jump, balance, and sprint performance were measured before exercise, immediately after exercise, 1, 24, and 48 h. after exercise. All the variables were checked regarding their normal distribution using the Shapiro-Wilk test and data were presented as means ±SD. A repeated-measure, two factor ANOVA was used to examine differences between the four trials over time for balance, speed, vertical jump, hunger, and muscle pain change. No differences were found at baseline values for balance, velocity, vertical jump, hunger, and muscle pain for four trials (p > 0.05). While the main effect of time was statistically significant for balance, speed, vertical jump, hunger, and muscle pain (p

Abstract Background Eccentric muscle contraction can cause muscle damage, which reduces the efficiency of exercise. Previous evidence suggested that Sodium salicylate (SS) could improve the repair of aged muscle. This study intends to investigate whether SS can impact skeletal muscle damage caused by eccentric exercise. Methods Eccentric treadmill exercise was performed to induce muscle damage in mice. Plasma levels of muscle damage markers were estimated. RT-qPCR was employed for detecting mRNA levels of proinflammatory mediators in murine gastrocnemius muscle. Immunofluorescence staining of laminin/DAPI was utilized for quantifying centrally nucleated myofibers in the gastrocnemius muscle. Western blotting was implemented to examine protein levels of mitsugumin 53 (MG53), matrix metalloproteinase (MMP)-2/9, and NF-κB signaling-related markers. Results SS administration reduced muscle damage marker production in the plasma and decreased the levels of proinflammatory mediators, MG53 and MMP-2/9 in mice after exercise. SS alleviated the severity of muscle damage in the gastrocnemius of mice after eccentric exercise. SS blocked NF-κB signaling pathway in the gastrocnemius muscle. Conclusion SS administration ameliorates skeletal muscle damage caused by eccentric exercise in the mouse model.

Introduction: The main generator of delayed onset muscle soreness (DOMS) is still unknown. This study aimed to clarify the main generator of DOMS. Methods: Twelve participants performed eccentric exercise (EE) on lower legs. MRI and ultrasound were used to assess changes of calf muscle and deep fascia before and after EE. These results were then compared to the muscle pain level. Results: Compared to baseline, muscle pain peaked at 24–48 h after EE (downstairs 22.25 ± 6.196, 57.917 ± 9.298, F = 291.168, p < 0.01; resting 5.833 ± 1.899, 5.083 ± 2.429, F = 51.678, p < 0.01). Shear wave speed (SWE) of the deep fascia and T2 values of the gastrocnemius muscle and deep fascia all increased and peaked at 48 h after EE (1.960 ± 0.130, F = 22.293; 50.237 ± 2.963, F = 73.172; 66.328 ± 2.968, F = 231.719, respectively, p < 0.01). These measurements were positively correlated with DOMS (downstairs: r = 0.46, 0.76, 0.87, respectively, p < 0.001; resting: r = 0.42, 0.70, 0.77, respectively, p < 0.001). There was a significant positive correlation between SWE and T2 values of deep fascia (r = 0.54, p < 0.01). Conclusion: DOMS is a common result of muscle and fascia injuries. Deep fascia edema and stiffness play a crucial role in DOMS, which can be effectively evaluated MR-T2 and SWE. Critical relevance statement: Delayed-onset muscle soreness is a common result of muscle and deep fascia injuries, in which the edema and stiffness of the deep fascia play a crucial role. Both MRI and shear wave elastography can be effectively used to evaluate soft tissue injuries. Key points: • The deep fascia is the major pain generator of delayed-onset muscle soreness. • There is a significant correlation between fascia injury and delayed-onset muscle soreness. • MRI and shear wave elastography are preferred methods for assessing fascia injuries. [ABSTRACT FROM AUTHOR]

Introduction: The aim of this study was to compare vastus lateralis (VL) and rectus femoris (RF) muscles for their nervous and mechanical adaptations during two bouts of downhill walking (DW) with load carriage performed 2 wk apart. Moreover, we investigated cardiometabolic and perceived exertion responses during both DW bouts. Methods: Seventeen participants performed two 45-min sessions of loaded DW (30% of body mass; slope, −25%; speed, 4.5 km·h−1) separated by 2 wk. Rating of perceived exertion, cost of walking, heart rate, and EMG activity of thigh muscles were assessed during the DW. Muscle shear elastic modulus (μ) of RF and VL were assessed before each exercise bout. Maximal voluntary contraction torque was assessed before (PRE), immediately after (POST), and 24 and 48 h after the two exercise bouts. Results: Maximal voluntary contraction torque decreased from POST (−23.7% ± 9.2%) to 48 h (−19.2% ± 11.9%) after the first exercise (Ex1), whereas it was significantly reduced only at POST (−14.6% ± 11.0%) after the second exercise (Ex2; P < 0.001). Rating of perceived exertion (Ex1: 12.3 ± 1.9; Ex2: 10.8 ± 2.0), heart rate (Ex1: 156 ± 23 bpm; Ex2: 145 ± 25 bpm), cost of walking (Ex1: 4.5 ± 0.9 J·m−1·kg−1; Ex2: 4.1 ± 0.7 J·m−1·kg−1), and RF EMG activity (Ex1: 0.071 ± 0.028 mV; Ex2: 0.041 ± 0.014 mV) were significantly decreased during Ex2 compared with Ex1 (P < 0.01). RF μ was significantly greater in Ex2 (0.44 ± 0.18) compared with Ex1 (0.56 ± 0.27; P < 0.001). Conclusions: The RF muscle displayed specific mechanical and nervous adaptations to repeated DW bouts as compared with VL. Moreover, the muscle adaptations conferred by the first bout of DW could have induced greater exercise efficiency, inducing lesser perceived exertion and cardiometabolic demand when the same exercise was repeated 2 wk later. [ABSTRACT FROM AUTHOR]

Erythrocyte rheological properties contribute to the dynamic regulation of vascular resistance to flow shear force, facilitating blood delivery from the heart to peripheral tissues. Despite improved physical performance, the effects of eccentric cycling training (ECT) on erythrocyte rheological characteristics remain unclear. This study investigates the distinct effects of ECT and concentric cycling training (CCT) on muscular hemodynamic and erythrocyte rheological responses to exercise. Thirty‐nine sedentary healthy males were randomly assigned to either ECT (n = 13) or CCT (n = 13) at 45%–70% of the maximal workload for 30 min/day, 5 days/week for 6 weeks, or to a control group (n = 13) that did not receive any exercise intervention. A graded exercise test (GXT) was performed before and after the intervention. Muscular hemodynamic and erythrocyte rheological responses to the GXT were determined by near‐infrared spectroscopy and ektacytometry, respectively. Both ECT and CCT significantly enhanced perfusion (Δ[THb]VL) and O2 extraction (Δ[HHb]VL) in vastus lateralis during GXT. Before training, an acute GXT significantly reduced erythrocyte deformability and increased aggregability, whereas after 6 weeks of either ECT or CCT, the extent of erythrocyte rheological changes caused by GXT was diminished. Moreover, CCT elicited higher improvements in cardiac output (CO), VO2, and work‐rate at peak performance than ECT. In hierarchical regression, the change of maximal CO was the most influential factor affecting VO2max following CCT. In contrast, enhanced VO2max was significantly associated with Δ[HHb]VL and erythrocyte aggregability/deformability in ECT. Although CCT is superior to ECT for increasing aerobic capacity, either ECT or CCT effectively enhances aerobic efficiency by improving muscular hemodynamic and erythrocyte rheological responses to exercise. Highlights: Although concentric cycling training (CCT) is superior to eccentric cycling training (ECT) for increasing aerobic capacity, the two regimens effectively enhance aerobic efficiency by improving hemodynamic or/and hemorheological response(s) to exercise.ECT increases blood O2 delivery to and utilization by contracting muscles, while having lower exertional cardiovascular demand compared to CCT.Cardiac hemodynamic function is the most dominant factor affecting the change of aerobic capacity caused by CCT.Muscular hemodynamic and erythrocyte rheological functions are meaningfully associated with aerobic efficiency mediated by ECT. [ABSTRACT FROM AUTHOR]

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Background: Lateral epicondylitis is considered to be the most prevalent overuse injury which affects 1% to 3% of the total population among all age groups and genders. The tendon of extensor carpi radialis brevis gets affected and can be strengthened by resistance exercises. It also affects plumbers, carpenters, housewives etc. The daily activities are interrupted which increases pain in lateral epicondylitis can be treated conservatively and surgically. Purpose: To compare the effectiveness of concentric vs Eccentric training programs for lateral epicondylitis by reducing pain. Materials and Methods: 68 subjects were selected from Active physio care physiotherapy clinic based on the inclusion and exclusion criteria. The detailed procedure for performing the study was explained to the subjects, and the informed consent form was collected from them before starting the study. The pre and post test values were measured using the numerical pain rating scale (NPRS) and pain rated tennis elbow evaluation (PRTEE). The subjects selected based on the inclusion and exclusion criteria were divided into two groups: concentric group and Eccentric group (n = 34). Study period: November 2022 to April 2023. Results: Statistical analysis of numerical pain rating scale and pain rated tennis elbow evaluation post test result revealed that both groups show similar effect but Eccentric exercise Group (Group B) exceeds Concentric Exercise group (Group A) with p VALUE of p<0.0001. Conclusion: When comparing the concentric group to the Eccentric group, the Eccentric group indicates significant effects in improving the strength of the elbow, improving the functional activity and strength of the forearm [ABSTRACT FROM AUTHOR]

Background: Inflammation of the extensor Carpi Radialis Brevis tendon causes lateral epicondyle discomfort. Patients on the dominant side were more affected than those on the nondominant side. And also proximal muscle weakness or instability places an additional load on the distal joint, leading to distal conditions, such as lateral epicondylitis. Purpose: To evaluate the effectiveness of scapular strengthening exercise and forearm eccentric exercise on functional recovery in subjects with lateral epicondylitis. Materials and Methods: Thirty participants were randomly assigned to experimental (scapular strengthening with eccentric exercise) and conventional (eccentric exercise) groups. Pain-rated tennis elbow evaluation (PRTEE), the numerical pain rating scale (NPRS), and grip strength measurement using a hand dynamometer were used to evaluate the pre-test. The same test was used to determine post-treatment values after five weeks of treatment. Results: A substantial difference was seen between the experimental and control groups (P = 0.0001). Scapular strengthening and eccentric exercises were effective in patients with lateral epicondylitis. Conclusion: Scapular muscle strengthening and eccentric forearm training are effective in individuals with lateral epicondylitis. [ABSTRACT FROM AUTHOR]

Isokinetic dynamometry is the clinical gold standard for strength assessment but testing protocols and outcome metrics can lack functional relevance. To quantify the influence of dynamometer configuration on eccentric hamstring strength metrics, 23 trained participants completed isokinetic eccentric knee flexor trials at 180°·s−1 in a seated and extended hip position. The extended position elicited a greater peak torque (P = 0.04) which was achieved at a significantly (P < 0.001) greater degree of knee flexion. Isokinetic range and functional range (defined as 85% of peak torque) were consistent at ~44° and ~21°, respectively, across trials, but were achieved with a more flexed knee in the extended hip configuration. Therefore, whilst the extended hip configuration might better reflect the biarticular nature of the hamstring musculature and the mechanism of hamstring strain injury, the sensitivity of strength metrics to configuration has implications for clinical assessment and training adaptations. [ABSTRACT FROM AUTHOR]

Effects of plant-and animal-based meals on serum nitric oxide and peroxynitrite levels after high-intensity eccentric exercise: A randomized crossover study. Adv. Exerc. Sports Physiol., Vol.29, No.3 pp.37-47, 2024. High-intensity eccentric exercise (ECC) temporarily in-duces endothelial dysfunction. Increased production of nitric oxide (NO) without peroxynitrite generation is essential for improving endothelial function. Plant proteins, such as soy and pea, decrease oxidative stress and increase endothelial NO generation. There-fore, plant-based meals may influence the balance between NO and peroxynitrite after high-intensity ECC. This study aimed to evaluate the effect of plant-based meals on serum NO levels (measured as the stable end product of NO, i.e., nitrite/nitrate [NOx]), peroxynitrite (measured as 3-nitrotyrosine), and NO/per-oxynitrite balance (measured as serum NOx/3-nitrotyrosine bal-ance) after a single bout of ECC. A randomized crossover trial was performed in 14 young adults (aged 22-29 years). Participants consumed animal-based meals (ABM) or plant-based meals (PBM) for 1 day after high-intensity ECC, constituting 50 repeti-tions of maximal elbow flexion. The PBM contained no animal proteins, while the ABM contained 11% animal proteins. Both meals contained the same total energy, protein, fat, and carbohy-drate. Standard meals were provided a day before the baseline measurement. Venous blood samples were taken at baseline and 24 h after ECC. Cardiovascular hemodynamics, muscle damage, soreness, and maximal isometric force were measured at baseline and immediately and 24 h after ECC. The results showed that se-rum NOx levels were significantly reduced 24 h after ECC in the ABM condition (P<0.05); however, it did not change in the PBM condition (P = 0.72). There was no significant interaction for se-rum 3-nitrotyrosine levels (P = 0.08). PBM consumption signifi-cantly increased the serum NOx/3-nitrotyrosine balance, whereas ABM decreased it after ECC (P<0.01). There were no significant interaction effects for other variables. These results suggest that a diet replacing animal proteins with plant proteins for a day pre-vents the reduction of NO production and improves the balance between NO and peroxynitrite after high-intensity ECC [ABSTRACT FROM AUTHOR]

The present study compared the ipsilateral repeated bout effect (IL‐RBE) and contralateral repeated bout effect (CL‐RBE) of the elbow flexors (EF) and knee flexors (KF) for the same interval between bouts to shed light on their mechanisms. Fifty‐two healthy sedentary young (20–28 years) men were randomly assigned to the IL‐EF, IL‐KF, CL‐EF, and CL‐KF groups (n = 13/group). Thirty maximal eccentric contractions of the EF were performed in IL‐EF and CL‐EF, and 60 maximal eccentric contractions of the KF were performed in IL‐KF and CL‐KF, with a 2‐week interval between bouts. Changes in muscle damage markers such as maximal voluntary contraction (MVC) torque, muscle soreness, and plasma creatine kinase activity, and proprioception measures before to 5 days post‐exercise were compared between groups. Changes in all variables were greater (p < 0.05) after the first than second bout for all groups, and the changes were greater (p < 0.05) for the EF than KF. The changes in all variables after the second bout were greater (p < 0.05) for the CL than IL condition for both EF and KF. The magnitude of the average protective effect was similar between CL‐EF (33%) and CL‐KF (32%), but slightly greater (p < 0.05) for IL‐EF (67%) than IL‐KF (61%). These demonstrate that the magnitude of CL‐RBE relative to IL‐RBE was similar between the EF and KF (approximately 50%), regardless of the greater muscle damage for the EF than KF. It appears that the CL‐RBE is more associated with neural adaptations at cerebrum, cerebellum, interhemispheric inhibition, and coricospinal tract, but the IL‐RBE is induced by additional adaptations at muscles. [ABSTRACT FROM AUTHOR]

We aimed to investigate the impact of pistachio nut consumption on muscle soreness and function following exercise-induced muscle damage. Using a randomised cross-over design, male teamsport players (n = 18) performed a 40-minute downhill treadmill run to induce muscle damage, which was conducted after 2-wks of consuming either control (CON, water), a standard dose of daily pistachios (STD, 42.5 g/d) or a higher dose of daily pistachios (HIGH, 85 g/d). Lower limb muscle soreness (visual analogue scale), muscle function (maximal voluntary isokinetic torque and vertical jump), and blood markers of muscle damage/inflammation (creatine kinase, Creactive protein, myoglobin, superoxide dismutase) were measured pre (baseline) and post (24, 48, and 72 h) exercise. No trial order effects were observed for any outcome measurement across trials. Mean quadriceps soreness (non-dominant leg) during exercise recovery was reduced (p < 0.05) in HIGH vs. CON (mean difference (95%CI): 13(1-25) mm). Change in soreness in the dominant quadriceps was not different between HIGH vs. CON (p = 0.06; mean difference (95%CI): 13(-1 to 26 mm)). No main effects of time or trial were observed for mean soreness of hamstrings, or on isokinetic torque of knee extensors or knee flexors, during recovery. Serum creatine kinase concentration peaked at 24 h post-damage (mean(SEM): 763(158)µg/L) from baseline (300(87)µg/L), but had returned to baseline by 72 h post (398(80)µg/L) exercise in all trials, with no trial or trial × time interaction evident. These data suggest that high dose pistachio nut ingestion may provide some alleviation of muscle soreness, but no effect on muscle function, following modest muscle damage. [ABSTRACT FROM AUTHOR]

Background. Eccentric exercise may trigger mechanical stress, resulting in muscle damage that may decrease athletic performance. L-citrulline potentially prevents skeletal muscle damage after acute eccentric exercise. This study aimed to assess the dose-response effect of L-citrulline as a preventive therapy for skeletal muscle damage in mice after acute eccentric exercise. Methods. This is a controlled laboratory in vivo study with a post-test-only design. Male mice (BALB/c, n=25) were randomized into the following groups: a normal control (C1) (n=5); a negative control (C2) with downhill running and placebo intervention (n=5); treatment groups: T1 (n=5), T2 (n=5), and T3 (n=5), were subjected to downhill running and 250, 500, and 1,000 mg/kg of L-citrulline, respectively, for seven days. Blood plasma was used to determine the levels of TNNI2 and gastrocnemius muscle tissue NOX2, IL-6, and caspase 3 using ELISA. NF-χB and HSP-70 expressions were determined by immunohistochemistry. Results. Skeletal muscle damage (plasma TNNI2 levels) in mice after eccentric exercise was lower after 250 and 500 mg/kg of L-citrulline. Further, changes in oxidative stress markers, NOX2, were reduced after a 1,000 mg/kg dose. However, a lower level of change has been observed in levels of cellular response markers (NF-κB, HSP-70, IL-6, and caspase 3) after administration of L-citrulline doses of 250, 500, and 1,000 mg/kg. Conclusion. L-citrulline may prevent skeletal muscle damage in mice after acute eccentric exercise through antioxidant effects as well as inflammatory and apoptotic pathways. In relation to dose-related effects, it was found that L-citrulline doses of 250, 500, and 1,000 mg/kg significantly influenced the expression of NF-κB and HSP-70, as well as the levels of IL-6 and caspase 3. Meanwhile, only doses of 250 and 500 mg/kg had an impact on TNNI2 levels, and the 1,000 mg/kg dose affected NOX2 levels. [ABSTRACT FROM AUTHOR]

This study examined the effect of repeated bouts of level and downhill running on physiological markers of effort and exercise-induced muscle soreness in trained female distance runners. Ten participants (Age: 24.4 ± 2.0 years; V̇O2peak: 52.9 ± 1.1 mL·kg−1·min−1), naïve to downhill running, completed six alternate 5 min trials of level and downhill running (−15%) at a 70% velocity at V̇O2peak on two occasions, three weeks apart. Perceived muscle soreness was measured upon completion and in the 72 h post exercise. V̇O2, Heart Rate (HR), Blood Lactate (BLa), and Respiratory Exchange Ratio (RER) were lower running downhill (p < 0.016, ηp2 > 0.541). For the first downhill run, Rating of Perceived Exertion (RPE) was higher compared to that for level running (p = 0.051; d = 0.447), but for the remaining trials, RPE was lower when running downhill (p < 0.004; d > 0.745). V̇O2, HR, and RER were not different in the second bout (p > 0.070, ηp2 < 0.318); however, V̇O2 was lower in each downhill trial (Δ = 1.6–2.2 mL·kg−1·min−1; d = 0.382–0.426). In the second bout, BLa was lower (p = 0.005, ηp2 = 0.602), RPE in the first trial was lower (p = 0.002; d = 0.923), and post exercise perceived soreness of the gastrocnemius, quadriceps, and hamstrings was attenuated (p < 0.002; ηp2 > 0.693). Perceived soreness of the gluteal muscles was lower in the second bout immediately post exercise, 24 h, and 48 h post exercise (p < 0.025; d > 0.922). A repeated bout of downhill running attenuated perceived muscle soreness and may modulate the physiological and perceived physical demand of a second bout of level and downhill running.