Eccentric Exercise-induced Muscle Damage Research Articles

Eccentrically-Induced Fatigue in Voluntary Muscle Performance: the Effect of Muscle Length and Contraction Type

Research background and hypothesis. We hypothesized that eccentric exercise (EE) would induce muscle fatigue and damage, which are dependent not only on muscle length tested but and on contraction type (eccentric vs. concentric vs. isometric) as well.Research aim was to test the hypothesis.Research methods. Healthy untrained men (mean ± SD: age = 24.8 ± 3.7 years, n = 10) performed 10 series of 12 repetitions of eccentric knee contractions at 160 deg/s. The maximal voluntary isometric contraction force (MVC) of the quadriceps muscle, the maximal rate of torque development (RTD) and isokinetic torque at 30 deg/s were established before and after EE. All measures were performed at different knee angles. Besides, the EMG of the quadriceps muscle was measured.Research results showed a significant change in absolute values of RTD after EE (before EE: 3695 ± 803 N∙m/s and 2360 ± 695 N∙m/s at SL and LL respectively; after EE: 2574 ± 843 N∙m/s and 1517 ± 476 N∙m/s at SL and LL respectively). A significant difference between EMG (rms) in MVC was found after EE at LL and SL, i. e. in v.lateralis 0.32 ± 0.12 mV and 0.24 ± 0.1 mV and in r.femoris 0.25 ± 0.11 mV and 0.17 ± 0.07 mV respectively. All criteria of voluntary performance changed significantly after EE except for R TD, i.e. it increased after EE.Discussion and conclusions. We observed more changes in isokinetic torque at shorter muscle length after eccentric exercise-induced muscle fatigue and damage. The changes in MVC and RTD after eccentric exercise did not depend on the length of the muscle tested. Besides, relative RTD did not change after exercise.Keywords: eccentric, concentric and isometric contraction; muscle fatigue and damage; muscle length, muscle force; rate of muscle torque development.

Metabolic Profiling of Eccentric Exercise-Induced Muscle Damage in Human Urine

Skeletal muscle can be ultrastructurally damaged by eccentric exercise, and the damage causes metabolic disruption in muscle. This study aimed to determine changes in the metabolomic patterns in urine and metabolomic markers in muscle damage after eccentric exercise. Five men and 6 women aged 19∼23 years performed 30 min of the bench step exercise at 70 steps per min at a determined step height of 110% of the lower leg length, and stepping frequency at 15 cycles per min. 1H NMR spectral analysis was performed in urine collected from all participants before and after eccentric exercise-induced muscle damage conventionally determined using a visual analogue scale (VAS) and maximal voluntary contraction (MVC). Urinary metabolic profiles were built by multivariate analysis of principal component analysis (PCA) and orthogonal partial least square-discriminant analysis (OPLS-DA) using SIMCA-P. From the OPLS-DA, men and women were separated 2 hr after the eccentric exercise and the separated patterns were maintained or clarified until 96 hr after the eccentric exercise. Subsequently, urinary metabolic profiles showed distinct trajectory patterns between men and women. Finally, we found increased urinary metabolites (men: alanine, asparagine, citrate, creatine phosphate, ethanol, formate, glucose, glycine, histidine, and lactate; women: adenine) after the eccentric exercise. These results could contribute to understanding metabolic responses following eccentric exercise-induced muscle damage in humans.

Adding omega-3 fatty acids to a protein-based supplement during pre-season training results in reduced muscle soreness and the better maintenance of explosive power in professional Rugby Union players

Evidence suggests that omega-3 fatty acid supplementation could reduce muscle soreness and maintain muscle function following eccentric exercise-induced muscle damage. The aim of this applied field study was to investigate the effectiveness of consuming a protein-based supplement containing 1546 mg of omega-3 polyunsaturated fatty acid (PUFA) (551 mg eicosapentaenoic acid (EPA) and 551 mg docosahexaenoic acid (DHA)) twice daily (FO) compared to a protein-based placebo (P) on muscle soreness, countermovement jump (CMJ) performance and psychological well-being in 20 professional Rugby Union players during 5 weeks of pre-season training. Players completed a 5-point-Likert soreness scale with 5 indicating “no soreness” and a questionnaire assessing fatigue, sleep, stress and mood each morning of training, plus they performed CMJ tests once or twice per week. Data were analysed using magnitude-based inferential statistics and are presented as percent beneficial/trivial/harmful. On day 35, there was a likely (% beneficial/trivial/harmful: 94/5/1) moderate (0.75, standardized mean difference (SMD)) beneficial effect of FO vs. P on the change in lower body muscle soreness compared with day 0 (FO: −3.8 ± 21.7%; P: −19.4 ± 11.2%). There was a likely (92/7/0) moderate (SMD: 0.60) beneficial effect of FO vs. P on CMJ performance (change from baseline to day 35, FO: +4.6 ± 5.9%; P: −3.4 ± 8.6%). From day 20, a moderate beneficial effect of FO on fatigue was observed. In terms of practical relevance, the moderate beneficial effect of adding fish oil to a protein-based supplement on muscle soreness translated into the better maintenance of explosive power in elite Rugby Union players during pre-season training.

Muscle fiber conduction velocity of the vastus medilais and lateralis muscle after eccentric exercise induced-muscle damage

Change in muscle fiber conduction velocity (MFCV) has been reported after eccentric exercise induces muscle fiber damage, most likely due to a change in membrane permeability of the injured fiber. The extent of damage to the muscle fiber depends on the morphological and architectural characteristics of the muscle fibers. Morphological and architectural characteristics of the VMO muscle fibers are different from VL muscle. Thus, it is expected that eccentric exercise of quadriceps muscle results in a non-uniform fiber damage within the VMO and VL muscle and, as a consequence, non-uniform changes in membrane excitability and conduction velocity. The aim of the study was to investigate MFCV of the VMO and VL muscles before and 24 h after eccentric exercise. Multichannel surface EMG signals were concurrently recorded from the right VMO and VL muscles of 15 healthy men during sustained isometric contractions at 50% of the maximal force. Maximal voluntary force significantly reduced after eccentric exercise with respect to the pre-exercise condition (P < 0.0001). MFCV decreased over time during the sustained contractions at faster rates when assessed 24 h after exercise (VMO = −26.1; VL = −20.1) with respect to the pre-exercise condition (VMO = −9.1; VL = −13.7, P < 0.0001). Moreover, VMO showed a greater rate of reduction in MFCV over sustained contraction (26.1 ± 10.7%) in comparison with VL muscle (20.1 ± 8.5%, P < 0.025) 24 h after eccentric exercise. The result indicates that eccentric exercise contributes to a larger reduction in MFCV within the VMO muscle as compared to the VL muscle. This may abolish the ability of VMO to counteract the lateral pull of the VL muscle during knee extension, thereby leaving the knee complex more vulnerable to injury.

Effectiveness of Fish Oil Supplementation in Attenuating Exercise-Induced Muscle Damage in Women During Midfollicular and Midluteal Menstrual Phases.

McKinley-Barnard, SK, Andre, TL, Gann, JJ, Hwang, PS, and Willoughby, DS. Effectiveness of fish oil supplementation in attenuating exercise-induced muscle damage in females during midfollicular and midluteal menstrual phases. J Strength Cond Res 32(6): 1601-1612, 2018-The purpose of this study was to determine whether the differences in estrogen levels during the female menstrual cycle and fish oil supplementation would attenuate eccentric exercise-induced muscle damage and delayed-onset muscle soreness (DOMS). In a double-blind fashion, 22 physically active females (20.9 ± 1.4 years, 63.5 ± 9.0 kg, 165.2 ± 7.5 cm) were randomly assigned to ingest either 6 g of fish oil (n = 11) or placebo (n = 11) daily for 21 days. Participants underwent an eccentric exercise bout of the knee extensors on 2 occasions during the midfollicular (MF) and midluteal (ML) phases of the 28-day menstrual cycle. Before (PRE), at 6 (6HRPOST), and at 24 hours postexercise (24HRPOST) for each session, participants underwent assessments of DOMS, muscle strength, and had venous blood samples and muscle biopsies obtained. Data were analyzed using a 2 × 2 × 3 repeated-measures multivariate analysis of variance for each criterion variable (p ≤ 0.05). Further analysis of the main effects for the test was performed using separate 1-way analyses of variance. Delayed-onset muscle soreness was significantly greater at the 6HRPOST and 24HRPOST timepoints compared with PRE (p < 0.001). Superoxide dismutase and tumor necrosis factor-alpha (TNF-α) concentrations were significantly higher at the MF phase compared with the ML phase (p < 0.001 and p = 0.05, respectively). There were no statistically significant differences observed for muscle strength, myoglobin, NF-Kβ p50, or NF-Kβ p65. This study demonstrates that higher levels of estrogen may exert a cytoprotective effect on the sarcolemma.

Platycodon grandiflorum-derived saponin enhances exercise function, skeletal muscle protein synthesis, and mitochondrial function

Lower physical performance is an important risk factor in hypokinetic-related chronic disease, metabolic syndrome, and muscle atrophy. Our previous research demonstrated that Platycodon grandiflorum-derived saponin (PS) protects against eccentric exercise-induced muscle damage and mitochondrial function-related peroxisomal acyl-coenzme A oxidase (ACOX-1) and carnitine palmitoyltransferase (CPT-1) in high-fat diet-induced non-alcoholic steatohepatitis, and it inhibits osteoclast differentiation. However, the effects of PS on physical performance remain unknown. Therefore, we investigated whether PS enhances physical activity and skeletal muscle function. Supplementation with PS (2 mg/kg for 4 weeks) increased grip strength, wheel running repetition, and time to exhaustion in treadmill and swimming exercises. Marked increases in the synthesis of skeletal muscle proteins and muscle stem cell-related paired-box 7 (PAX7) were observed, and a decrease in the negative regulator myostatin was associated with enhanced muscle regeneration. Furthermore, PS induced expression of mitochondrial function proteins, including OXPHOS-III and -IV, in vivo and in vitro. These results suggest that PS enhances exercise function by ameliorating skeletal muscle protein synthesis and mitochondrial function.

Hormonal Responses after Exercise-induced Muscle Damage in Healthy Humans

Mechanically overloaded muscle and its subsequent damage are strong stimuli for eliciting acute hormonal changes, and muscle adaptation following exercise- induced muscle damage may involve complex hormonal responses before the completion of muscle regeneration. PURPOSE: This study investigated systemic responses of thyroid-stimulating hormone (TSH), free thyroxine (fT4) and prolactin (PRL) for several days after eccentric exercise-induced muscle damage in humans. METHODS: Nine healthy men (age 25.7 ± 1.7 years, height 180.4 ± 1.7 cm, body mass 77.2 ± 2.7 kg, body mass index 23.7 ± 0.6) performed 50 maximal eccentric muscle actions using the knee extensor muscles of both legs on an isokinetic dynamometer. Blood samples were withdrawn before and at 6, 48 and 120 hrs post-exercise, and serum levels of TSH, fT4) and PRL were measured by ELISA using commercially available kits. Myoglobin (Mb) concentration and lactate dehydrogenase (LDH) activity were also evaluated as indirect markers of muscle damage. One-way ANOVA was used for statistics. RESULTS: Significant alterations in Mb and LDH were observed over time after eccentric exercise (p<0.05-0.001). Serum fT4 levels exhibited a gradual increase reaching statistical significance at 48 and 120 hrs following the muscle damaging exercise (1.20±0.05 ng/dl, 1.29±0.04 ng/dl, and 1.26±0.05 ng/dl, at 6, 48 and 120 hours after exercise, respectively, compared to 1.13±0.02 ng/dl at baseline; mean±SE, p<0.05). Both PRL and TSH showed also a gradual increase up to 33% at 48 hrs and 120 hrs post exercise, respectively, however they failed to reach statistical significance due to a large variability shown between the subjects’ responses (PRL: 23.4±3.1 ng/ml, 28.1±4.7 ng/ ml, 30.2±4.1 ng/ml and 25.7±4.6 ng/ml; TSH: 1.09±0.14 μIU/ml, 1.27±0.15 μIU/ml, 1.17±0.20 μIU/ml, and 1.33±0.17 μIU/ml, at baseline, 6, 48 and 120 hours post- exercise, respectively, mean±SE, p>0.05). CONCLUSION: The late elevated levels of TSH and PRL, and particularly of fT4, during the recovery period after muscle damage may suggest functional interactions between those hormones and muscle regeneration. Further studies are needed to characterize the mechanisms by which those hormonal responses are triggered and regulated at the systemic level during recovery after exercise-induced muscle damage.

Effects of Isometric Contractions on Eccentric Exercise-induced Muscle Damage of the Knee Extensors

Effects of Isometric Contractions on Eccentric Exercise-induced Muscle Damage of the Knee Extensors

Effects of Two Maximal Isometric Contractions Attenuate Eccentric Exercise-induced Muscle Damage on Surface Electromyographic Activity

Tseng et al. (2016) reported that changes in MaxECC-induced muscle damage (EIMD) of the preconditioning MVC training of the knee extensors (KE) for untrained men was significantly smaller than control group. No studies have recruited untrained participants, and targeted on hamstring muscle strains in which are the most frequent sporting injuries to clarify whether non-damaging exercise of MVC can be attenuated muscle damage induced by MaxECC of knee flexors (KF). PURPOSE: This study investigated the neural factors (surface electromyography, EMG) of two maximal isometric contractions (2MVC) at 20° knee flexion on changes in indirect muscle damage markers following 60 MaxECC of KF performed 2 days later. METHODS: Sixteen untrained young males were randomly placed into the control group (CON) that did not perform 2MVC, or the experimental group (2d, n = 8 per group) who performed 2MVC 2 days before MaxECC. Changes in muscle soreness (SOR), non-dominant upper thigh circumference (CIR), resting knee angle (RANG), maximal voluntary isokinetic concentric contraction (MVC-CON), and surface EMG [median frequency (MF), root mean square (RMS)] before, immediately after, and 1-5 days after MaxECC were compared between groups by a mixed-design of two-way ANOVA. RESULTS: 1). Significant (p < .05) changes in some dependent variables after 2MVC compared to baseline for the 2d group; 2). Changes in the muscle damage variables (e.g. MVC-CON: -13.1%; CIR: +1.5 mm) following MaxECC immediately for the 2d group were smaller than CON group (-22.4%; +4.8 mm); 3) Changes in the surface EMG activity following MaxECC for the 2d group showed smaller changes (MF: 60.2 ± 9.1 Hz) than CON group (70 ± 13.2 Hz). CONCLUSION: These results suggest that protective effect conferred by non-damaging exercise of 2MVC against subsequent MaxECC-induced muscle damage is likely to be related to neural adaptations. Therefore, the RBE protocol of this study may provide some useful information for men to minimize muscle damage when they start to participate exercise. It is also required to further understand the underpinning mechanisms of the repeated bout effect in both physiological and pathological contexts.

The effects of flexibility training on exercise-induced muscle damage in young men with limited hamstrings flexibility.

Adaptations to 6weeks of supervised hamstring stretching training and its potential impact on symptoms of eccentric exercise-induced muscle damage (EIMD) were studied in 10 young, untrained men with limited hamstrings flexibility. Participants performed unilateral flexibility training (experimental leg; EL) on an isokinetic dynamometer, while the contralateral limb acted as control (CL). Hip range of motion (ROM), passive, isometric, and concentric torques, active optimum angle, and biceps femoris and semitendinosus muscle thickness and ultrasound echo intensity were assessed both before and after the training. Additionally, muscle soreness was assessed before and after an acute eccentric exercise bout in both legs (EL and CL) at post-training only. Hip ROM increased (P<.001) only in EL after the training (EL=10.6° vs CL=1.6°), but no changes (P>.05) in other criterion measurements were observed. After a bout of eccentric exercise at the end of the program, isometric and dynamic peak torques and muscle soreness ratings were significantly altered at all time points equally in EL and CL. Also, active optimum angle was reduced immediately, 48 and 72hours post-exercise, and hip ROM was reduced at 48 and 72hours equally in EL and CL. Finally, biceps femoris muscle thickness was significantly increased at all time points, and semitendinosus thickness and echo intensity significantly increased at 72hours, with no significant differences between legs. The stretching training protocol significantly increased hip ROM; however, it did not induce a protective effect on EIMD in men with tight hamstrings.

Changes in central and peripheral neuromuscular fatigue indices after concentric versus eccentric contractions of the knee extensors.

To better understand neuromuscular characteristics of eccentric exercise-induced muscle damage, this study compared between concentric (CONC) and eccentric (ECC) exercises of knee extensor muscles, and the first (ECC1) and second bouts of the eccentric exercise (ECC2) for central and peripheral parameters associated with neuromuscular fatigue. Twelve young men performed three exercise bouts separated by at least 1week between CONC and ECC1, and 2weeks between ECC1 and ECC2. In each exercise, maximal voluntary concentric or eccentric contractions of the knee extensors were performed until a reduction in maximal voluntary isometric contraction (MVC) torque of at least 40% MVC was achieved immediately post-exercise. MVC torque, central (voluntary activation and normalised electromyographic activity), and peripheral neuromuscular indices (evoked torque and M-wave amplitude), and muscle soreness were assessed before (PRE), immediately after (POST), 1h (1H), and 1-4 days after exercise (D1, D2, D3, and D4). MVC torque decreased at only POST for CONC (- 52.8%), but remained below the baseline at POST (- 48.6%), 1H (- 34.1%), and D1-D4 (- 34.1 to - 18.2%) after ECC1, and at POST (- 45.2%), 1H (- 24.4%) and D1 (- 13.4%) after ECC2 (p < 0.05). Voluntary activation decreased immediately after ECC1 (- 21.6%) and ECC2 (- 21.1%), but not after CONC. Electrically evoked torques decreased similarly at POST and 1H for the three conditions, but remained below the baseline at D1 only post-ECC1. These results showed that both central and peripheral factors contributed to the MVC decrease after ECC1 and ECC2, but the decrease was mainly due to peripheral factors after CONC.

Hormonal responses following eccentric exercise in humans.

Mechanically overloaded muscle and its subsequent damage are strong stimuli for eliciting acute hormonal changes, while the muscle adaptation which occurs following exercise-induced muscle damage may involve complex hormonal responses before the completion of muscle regeneration. The purpose of this study was to investigate systemic responses of various hormones, as well as secreted proteins that are exercise-regulated and associated with muscle adaptation, for several days after eccentric exercise-induced muscle damage in humans. Nine young male volunteers performed 50 maximal eccentric muscle actions using the knee extensor muscles of both legs. Blood samples were drawn before and at 6, 48 and 120 hours post exercise and serum levels of growth hormone (GH), insulin-like growth factor binding protein-3 (IGFBP-3), cortisol, prolactin, thyroid-stimulating hormone (TSH), free thyroxine (fT4), irisin, follistatin and sclerostin were measured. Myoglobin (Mb) concentration and lactate dehydrogenase (LDH) activity were also evaluated as indirect markers of muscle damage. Significant alterations in Mb and LDH were observed over time after eccentric exercise (p=0.039-0.001). A late serum increase in fT4 and decrease in irisin levels, along with an early and persistent decrease in IGFBP-3 levels, were observed following the muscle-damaging exercise (p=0.049-0.016). GH, cortisol, prolactin, TSH, follistatin and sclerostin exhibited moderate changes during the recovery period after exercise, though without reaching statistical significance (p>0.05), while correlational analyses revealed significant associationsbetween GH and IGFBP-3, prolactin and sclerostin over time (p=0.049-0.001). The significant hormonal responses observed in this study may indicate their involvement in the regenerative mechanisms following muscle damage, potentially as part of a regulatory network to support a normal adaptation process after muscle-damaging exercise.

Influence of Maturation Status on Eccentric Exercise-Induced Muscle Damage and the Repeated Bout Effect in Females.

This study compared changes in indirect muscle damage markers, proprioception and arterial stiffness after elbow flexor eccentric exercise between pre-pubescent (9–10 y), pubescent (14–15 y), and post-pubescent (20–24 y) healthy, untrained females (n = 13/group). The maturation of the participants was confirmed by the hand bone age. All participants performed two bouts of 30 sub-maximal eccentric contractions (EC1, EC2) using a dumbbell set at 60% of pre-exercise maximal voluntary isometric elbow flexion strength at 90°. Changes in maximal voluntary concentric contraction (MVC) torque, muscle soreness (SOR), plasma creatine kinase activity, proprioception (position sense, joint reaction angle) and arterial stiffness (carotid-femoral pulse-wave velocity: cfPWV) before to 5 days after EC1 and EC2 were compared among groups by a mixed-design two-way ANOVA. Pre-exercise MVC torque and cfPWV were smaller (P < 0.05) for the pre-pubescent (MVC: 10.0 ± 0.9 Nm, cfPWV: 903 ± 60 cm/s) and the pubescent (14.3 ± 1.1 Nm, 967 ± 61 cm/s) than the post-pubescent (19.1 ± 1.4 Nm, 1,103 ± 73 cm/s). Changes in all variables after EC1 were smaller (P < 0.05) for the pre-pubescent (e.g., MVC at 1 d post-exercise: −10 ± 6%, peak SOR: 5 ± 2 mm) than the pubescent (−15 ± 9%, 12 ± 6 mm) and the post-pubescent (−25 ± 7%, 19 ± 13 mm). After EC2, changes in all variables were smaller (P < 0.05) than those after EC1 for all groups (e.g., MVC at 1 d post-exercise, pre-pubescent: −4 ± 6%, pubescent: −9 ± 4%, post-pubescent: −14 ± 5%; peak SOR: 3 ± 2, 7 ± 3, 11 ± 6 mm), but the magnitude of the repeated bout effect was not different (P > 0.05) among the groups. These results show that the extents of muscle damage, and proprioception and arterial stiffness changes after eccentric exercise are greater at later stages of maturation, but the repeated bout effect is not affected by maturation.

Ischemic Preconditioning Blunts Muscle Damage Responses Induced by Eccentric Exercise.

Ischemic preconditioning (IPC) is known to reduce muscle damage induced by ischemia and reperfusion injury during surgery. Because of similarities between the pathophysiological formation of ischemia and reperfusion injury and eccentric exercise-induced muscle damage (EIMD), as characterized by an intracellular accumulation of Ca, an increased production of reactive oxygen species, and increased proinflammatory signaling, the purpose of the present study was to investigate whether IPC performed before eccentric exercise may also protect against EIMD. Nineteen healthy men were matched to an eccentric-only (ECC; n = 9) or eccentric proceeded by IPC group (IPC + ECC; n = 10). The exercise protocol consisted of bilateral biceps curls (3 × 10 repetitions at 80% of the concentric one-repetition maximum). In IPC + ECC, IPC was applied bilaterally at the upper arms by a tourniquet (200 mm Hg) immediately before the exercise (3 × 5 min of occlusion, separated by 5 min of reperfusion). Creatine kinase (CK), arm circumference, subjective pain (visual analog scale score), and radial displacement (tensiomyography, maximal radial displacement) were assessed before IPC, preexercise, postexercise, and 20 min, 2 h, 24 h, 48 h, and 72 h postexercise. CK differed from baseline only in ECC at 48 h (P < 0.001) and 72 h (P < 0.001) postexercise. After 24, 48, and 72 h, CK was increased in ECC compared with IPC + ECC (between groups: 24 h, P = 0.004; 48 h, P < 0.001; 72 h, P < 0.001). The visual analog scale score was significantly higher in ECC at 24-72 h postexercise when compared with IPC + ECC (between groups: all P values < 0.001). The maximal radial displacement was decreased on all postexercise days in ECC (all P values < 0.001) but remained statistically unchanged in IPC + ECC (between groups: P < 0.01). These findings indicate that IPC performed before a bout of eccentric exercise of the elbow flexors blunts EIMD and exercise-induced pain while maintaining the contractile properties of the muscle.

Low-intensity elbow flexion eccentric contractions attenuate maximal eccentric exercise-induced muscle damage of the contralateral arm

ObjectivesThe magnitude of muscle damage induced by maximal eccentric contractions (MaxEC) of the elbow flexors (EF) is reduced when it is preceded by low-intensity (10% of maximal voluntary isometric contraction strength) eccentric contractions (10%EC) of the same muscle, or by MaxEC of the opposite EF. This study investigated whether 10%EC would reduce the magnitude of muscle damage after MaxEC performed by the opposite arm. DesignComparison among 6 groups for changes in indirect markers of muscle damage. MethodYoung (21.0±1.8years) untrained men were assigned to five experimental groups (n=13/group) that performed 30, 10%EC followed by 30 MaxEC of the other arm performed at either 1 (1d), 2 (2d), 7 (1wk), 14 (2wk) or 21days (3wk) later, and one control group that performed 30 MaxEC without 10%EC (n=13). Changes in several indirect markers of muscle damage after MaxEC were compared among the groups by mixed-design two-way ANOVAs. ResultsNo significant changes in maximal voluntary concentric contraction torque, plasma creatine kinase activity and muscle soreness were evident after 10%EC. Changes in these variables after MaxEC were smaller (p<0.05) for the 1d, 2d and 1wk groups than control group, without significant differences between the 1d, 2d and 1wk groups. No significance differences in the changes were evident among the 2wk, 3wk and control groups, except for muscle soreness showing smaller (p<0.05) increases for the 2wk and 3wk groups than control group. ConclusionsThese results showed that 10%EC conferred muscle damage protection to the contralateral arm that performed MaxEC.

Platycodon grandiflorum-derived saponin attenuates the eccentric exercise-induced muscle damage

Platycodon grandiflorum contains triterpenoid saponins, such as platycodin D and platyconic acid A, and acts as a multifold nutritious compound. Our previous research demonstrated that Platycodon grandiflorum-derived saponin (PS) improves high-fat diet-induced non-alcoholic steatohepatitis and inhibits osteoclast differentiation. The pivotal effects of PS on inflammatory mechanism were suppressed NF-κB and matrix metalloproteinase (MMPs). However, the effects of PS on skeletal muscle damage remain unknown. Therefore, we investigated whether PS protects against eccentric exercise-induced muscle damage. A significant reduction in eccentric exercise-induced muscle damage area and muscle damage related to the level of NF-κB p65 by PS was associated with the downregulation of ERK/p38/SMAD signaling. Eccentric exercise caused muscle damage by increasing the serum lactate dehydrogenase (LDH), creatinine kinase (CK) and C-related protein level. The serum LDH, CK and C-related protein level was significantly lower in the PS supplementation group compared with the control group. Moreover, PS was inhibited MMP-1, MMP-2 and MMP-9. PS protects against eccentric exercise-induced muscle damage. Together, these results provide a novel perspective on the biological function of PS against muscle damage.

The Effect of Taurine on the Recovery from Eccentric Exercise-Induced Muscle Damage in Males

Eccentric exercise is known to bring about microstructural damage to muscle, initiating an inflammatory cascade involving various reactive oxygen species. This, in turn, can significantly impair physical performance over subsequent days. Taurine, a powerful endogenous antioxidant, has previously been shown to have a beneficial effect on muscle damage markers and recovery when taken for a few days to several weeks prior to eccentric exercise. However, to date no studies have looked at the effects of supplementing over the days following eccentric exercise on performance recovery. Thus, this study aimed to determine whether supplementing with taurine over three days following eccentric exercise attenuated the rise in serum creatine kinase and improved performance recovery in males. In a blinded, randomized, crossover design, ten recreationally-fit male participants completed 60 eccentric contractions of the biceps brachii muscle at maximal effort. Following this, participants were supplemented with 0.1 g∙kg−1 body weight∙day−1 of either taurine or rice flour in capsules. Over the next three mornings participants underwent blood tests for the analysis of the muscle damage marker creatine kinase and carried out performance measures on the isokinetic dynamometer. They also continued to consume the capsules in the morning and evening. The entire protocol was repeated two weeks later on the alternate arm and supplement. Significant decreases were seen in all performance measures from pre- to 24-h post-eccentric exercise (p < 0.001) for both taurine and placebo, indicating the attainment of muscle damage. Significant treatment effects were observed only for peak eccentric torque (p < 0.05). No significant time × treatment effects were observed (all p > 0.05). Serum creatine kinase levels did not significantly differ over time for either treatments, nor between treatments (p > 0.05). These findings suggest that taurine supplementation taken twice daily for 72 h following eccentric exercise-induced muscle damage may help improve eccentric performance recovery of the biceps brachii.

Adding Fish Oil to Whey Protein, Leucine, and Carbohydrate Over a Six-Week Supplementation Period Attenuates Muscle Soreness Following Eccentric Exercise in Competitive Soccer Players.

Soccer players often experience eccentric exercise-induced muscle damage given the physical demands of soccer match-play. Since long chain n-3 polyunsaturated fatty acids (n-3PUFA) enhance muscle sensitivity to protein supplementation, dietary supplementation with a combination of fish oil-derived n-3PUFA, protein, and carbohydrate may promote exercise recovery. This study examined the influence of adding n-3PUFA to a whey protein, leucine, and carbohydrate containing beverage over a six-week supplementation period on physiological markers of recovery measured over three days following eccentric exercise. Competitive soccer players were assigned to one of three conditions (2 × 200mL): a fish oil supplement beverage (FO; n = 10) that contained n-3PUFA (1100mg DHA/EPA-approximately 550mg DHA, 550mg EPA), whey protein (15g), leucine (1.8g), and carbohydrate (20g); a protein supplement beverage (PRO; n = 10) that contained whey protein (15g), leucine (1.8g), and carbohydrate (20g); and a carbohydrate supplement beverage (CHO; n = 10) that contained carbohydrate (24g). Eccentric exercise consisted of unilateral knee extension/flexion contractions on both legs separately. Maximal force production was impaired by 22% during the 72-hour recovery period following eccentric exercise (p < 0.05). Muscle soreness, expressed as area under the curve (AUC) during 72-hour recovery, was less in FO (1948 ± 1091mm × 72h) than PRO (4640 ± 2654mm × 72h, p < 0.05) and CHO (4495 ± 1853mm × 72h, p = 0.10). Blood concentrations of creatine kinase, expressed as AUC, were ~60% lower in FO compared to CHO (p < 0.05) and tended to be lower (~39%, p = 0.07) than PRO. No differences in muscle function, soccer performance, or blood c-reactive protein concentrations were observed between groups. In conclusion, the addition of n-3PUFA to a beverage containing whey protein, leucine, and carbohydrate ameliorates the increase in muscle soreness and blood concentrations of creatine kinase following eccentric exercise in competitive soccer players.

Using Polyphenol-Based Soap Ameliorates Eccentric Exercise-Induced Muscle Damage

Using Polyphenol-Based Soap Ameliorates Eccentric Exercise-Induced Muscle Damage

Modulation of mitochondrial biomarkers by intermittent hypobaric hypoxia and aerobic exercise after eccentric exercise in trained rats.

Unaccustomed eccentric contractions induce muscle damage, calcium homeostasis disruption, and mitochondrial alterations. Since exercise and hypoxia are known to modulate mitochondrial function, we aimed to analyze the effects on eccentric exercise-induced muscle damage (EEIMD) in trained rats using 2 recovery protocols based on: (i) intermittent hypobaric hypoxia (IHH) and (ii) IHH followed by exercise. The expression of biomarkers related to mitochondrial biogenesis, dynamics, oxidative stress, and bioenergetics was evaluated. Soleus muscles were excised before (CTRL) and 1, 3, 7, and 14 days after an EEIMD protocol. The following treatments were applied 1 day after the EEIMD: passive normobaric recovery (PNR), 4 h daily exposure to passive IHH at 4000 m (PHR) or IHH exposure followed by aerobic exercise (AHR). Citrate synthase activity was reduced at 7 and 14 days after application of the EEIMD protocol. However, this reduction was attenuated in AHR rats at day 14. PGC-1α and Sirt3 and TOM20 levels had decreased after 1 and 3 days, but the AHR group exhibited increased expression of these proteins, as well as of Tfam, by the end of the protocol. Mfn2 greatly reduced during the first 72 h, but returned to basal levels passively. At day 14, AHR rats had higher levels of Mfn2, OPA1, and Drp1 than PNR animals. Both groups exposed to IHH showed a lower p66shc(ser36)/p66shc ratio than PNR animals, as well as higher complex IV subunit I and ANT levels. These results suggest that IHH positively modulates key mitochondrial aspects after EEIMD, especially when combined with aerobic exercise.