Bout Of Eccentric Exercise Research Articles

Does Intermittent Pneumatic Leg Compression Enhance Muscle Recovery after Strenuous Eccentric Exercise?

Intermittent pneumatic compression (IPC) has gained rapid popularity as a post-exercise recovery modality. Despite its widespread use and anecdotal claims for enhancing muscle recovery there is no scientific evidence to support its use. 10 healthy, active males performed a strenuous bout of eccentric exercise (3 sets of 100 repetitions) followed by IPC treatment or control performed immediately after exercise and at 24 and 48 h post-exercise. Muscular performance measurements were taken prior to exercise and 24, 48 and 72 h post-exercise and included single-leg vertical jump (VJ) and peak and average isometric [knee angle 75º] (ISO), concentric (CON) and eccentric (ECC) contractions performed at slow (30° · s⁻¹) and fast (180° · s⁻¹) velocities. Plasma creatine kinase (CK) samples were taken at pre- and post-exercise 24, 48 and 72 h. Strenuous eccentric exercise resulted in a significant decrease in peak ISO, peak and average CON (30° · s⁻¹) at 24 h compared to pre-exercise for both IPC and control, however VJ performance remained unchanged. There were no significant differences between conditions (IPC and control) or condition-time interactions for any of the contraction types (ISO, CON, ECC) or velocities (CON, ECC 30° · s⁻¹ and 180° · s⁻¹). However, CK was significantly elevated at 24 h compared to pre-exercise in both conditions (IPC and control). IPC did not attenuate muscle force loss following a bout of strenuous eccentric exercise in comparison to a control. While IPC has been used in the clinical setting to treat pathologic conditions, the parameters used to treat muscle damage following strenuous exercise in healthy participants are likely to be very different than those used to treat pathologic conditions.

Mild eccentric exercise increases Hsp72 content in skeletal muscles from adult and late middle-aged rats

The loss of muscle mass with age or sarcopenia contributes to increased morbidity and mortality. Thus, preventing muscle loss with age is important for maintaining health. Hsp72, the inducible member of the Hsp70 family, is known to provide protection to skeletal muscle and can be increased by exercise. However, ability to increase Hsp72 by exercise is intensity-dependent and appears to diminish with advanced age. Thus, other exercise modalities capable of increasing HSP content and potentially preventing the age related loss of muscle need to be explored. The purpose of this study was to determine if the stress from one bout of mild eccentric exercise was sufficient to elicit an increase in Hsp72 content in the vastus intermedius (VI) and white gastrocnemius (WG) muscles, and if the Hsp72 response differed between adult and late middle-aged rats. To do this, 30 adult (6 months) and late middle-aged (24 months) F344BN rats were randomly divided into three groups (n = 6/group): control (C), level exercise (16 m x min(-1)) and eccentric exercise (16 m x min(-1), 16 degree decline). Exercised animals were sacrificed immediately post-exercise or after 48 hours. Hematoxylin and Eosin staining was used to assess muscle damage, while Western Blotting was used to measure muscle Hsp72 content. A nested ANOVA with Tukey post hoc analysis was performed to determine significant difference (p < 0.05) between groups. Hsp72 content was increased in the VI for both adult and late middle-aged rats 48 hours after eccentric exercise when compared to level and control groups but no differences between age groups was observed. Hsp72 was not detected in the WG following any type of exercise. In conclusion, mild eccentric exercise can increase Hsp72 content in the rat VI muscle and this response is maintained into late middle-age.

Eccentric Exercise Increases Satellite Cell Content in Type II Muscle Fibers

Satellite cells (SCs) are of key importance in skeletal muscle tissue growth, repair, and regeneration. A single bout of high-force eccentric exercise has been demonstrated to increase mixed muscle SC content after 1-7 d of postexercise recovery. However, little is known about fiber type-specific changes in SC content and their activation status within 24 h of postexercise recovery. Nine recreationally active young men (23 ± 1 yr) performed 300 eccentric actions of the knee extensors on an isokinetic dynamometer. Skeletal muscle biopsies from the vastus lateralis were collected preexercise and 24 h postexercise. Muscle fiber type-specific SC content and the number of activated SCs were determined by immunohistochemical analyses. There was no difference between Type I and Type II muscle fiber SC content before exercise. SC content significantly increased 24 h postexercise in Type II muscle fibers (from 0.085 ± 0.012 to 0.133 ± 0.016 SCs per fiber, respectively; P < 0.05), whereas there was no change in Type I fibers. In accordance, activation status increased from preexercise to 24 h postexercise as demonstrated by the increase in the number of DLK1+ SCs in Type II muscle fibers (from 0.027 ± 0.008 to 0.070 ± 0.017 SCs per muscle fiber P < 0.05). Although no significant changes were observed in the number of Ki-67+ SCs, we did observe an increase in the number of proliferating cell nuclear antigen-positive SCs after 24 h of postexercise recovery. A single bout of high-force eccentric exercise increases muscle fiber SC content and activation status in Type II but not Type I muscle fibers.

Changes in skeletal muscle proteolytic gene expression after prophylactic supplementation of EGCG and NAC and eccentric damage

The impact of prophylactic supplementation of N-acetyl-cysteine (NAC) and epigallocatechin gallate (EGCG) on intramuscular expression of proteolytic genes after unaccustomed eccentric muscle contractions was investigated. Thirty apparently healthy males (mean ± SD: 20.0 ± 1.8 years, 175 ± 7.1cm, 76.1 ± 16.9 kg) ingested daily either 1,800 mg of NAC or 1,800 mg of EGCG (98% total polyphenols, 80% total catechins, and 50% EGCG), or 1,000 mg of a glucomannan placebo (PLA) in a double blind, prophylactic fashion for 14 days. Subjects then completed an unaccustomed eccentric exercise bout (100 repetitions at 30 °s(-1)) using the dominant knee extensors. Skeletal muscle biopsies were collected from the vastus lateralis at baseline and both 6 and 24h after exercise. The expression of proteolytic genes [i.e., muscle ring-finger 1 (MuRF1), atrogin-1, α-type 20S subunit C2 (HC2), α-type 20S subunit C3 (HC3), ubiquitin protein ligase 3B (UBE3B), μ-calpain, and m-calpain] was quantified using real-time RT-PCR. Separate 3 × 3 (group × time) repeated measures ANOVAs were used to analyze changes in gene expression over time between groups. No significant group × time interactions were detected between groups for the expression of any of the atrogenes or calpains (p>0.05). Significant main effects for time identified increases in MuRF1 (6h: 5.3 ± 10.8 fold; p=0.046), UBE3B (6h: 5.3 ± 7.7 fold; p=0.006; 24h: 3.3 ± 4.5 fold; p=0.005), and m-calpain expression (6h: 2.7 ± 4.4 fold; p=0.045) in all participants following exercise. Increases approached significance in HC2 (6h: 1.9 ± 2.4 fold; p=0.079; 24h: 1.6 ± 1.9 fold; p=0.084) and m-calpain expression (24h: 1.8 ± 2.3 fold; p=0.084) following exercise. Prophylactic supplementation of NAC and EGCG did not impact acute changes in skeletal muscle proteolytic gene expression following eccentric exercise. Eccentric muscle contractions elevated MuRF1 and UBE3B, while m-calpain and HC2 mRNA tended to increase.

Eccentric-exercise induced inflammation attenuates the vascular responses to mental stress

Mental stress has been identified as a trigger of myocardial infarction (MI), with inflammation and vascular responses to mental stress independently implicated as contributing factors. This study examined whether inflammation moderates the vascular responses to mental stress. Eighteen healthy male participants completed a stress task under two counter balanced conditions. In the exercise condition, a morning bout of eccentric exercise (12×5 repetitions of unilateral eccentric knee extension at 120% intensity of concentric one repetition maximum) was used to increase levels of inflammatory-responsive cytokines during an afternoon stress session scheduled 6h later. In the control condition, participants sat and relaxed for 45min, 6h prior to the afternoon stress session. Forearm blood flow, calf blood flow (measured in the leg which completed the exercise task), blood pressure, heart rate and cardiac output were assessed at rest and in response to mental stress. As expected, interleukin-6 was higher (p=.02) 6h post exercise, i.e., at the start of the stress session, as compared to the no-exercise control condition. Mental stress increased forearm blood flow, calf blood flow, blood pressure, heart rate, and cardiac output in both conditions (p's<.001). Stress-induced calf blood flow was attenuated in the exercise condition compared to the control condition (p<.05) which was not the case for forearm blood flow. This study found that the inflammatory response to eccentric exercise attenuated the vascular responses to mental stress locally at the site of eccentric exercise-induced inflammation. The observed impairment in vascular responses to stress associated with increased levels of inflammation suggests a mechanism through which inflammation might increase the risk for MI.

The effects of Panax notoginseng on delayed onset muscle soreness and muscle damage in well-trained males: A double blind randomised controlled trial

The aim of the study was to determine if Panax notoginseng is effective in reducing pain, indicators of inflammation and muscle damage, and in turn improve performance in well trained males who underwent a bout of eccentric exercise designed to induce delayed onset muscle soreness (DOMS). A double blind randomised placebo controlled trial. Twenty well trained male volunteers, matched by maximum aerobic capacity were randomly assigned to consume a regime of 4000 mg of P. notoginseng capsules or an indistinguishable placebo before and after a downhill treadmill running episode designed to induce DOMS. Performance measures (Kin-Com, counter movement and squat jump), pain assessments (visual analogue scale (VAS), algometer) and blood analyses (interleukin-1, interleukin-6 (IL-6), tumour necrosis factor-alpha (TNF-α), C-reactive protein, myoglobin, creatine kinase) were assessed at 7 time points over 5 days (pre, post, 4, 24, 48, 72 and 96 h after the downhill run). The placebo group demonstrated a significant decrease in squat jump performance immediately post the downhill run, with a mean change ± 95% confidence interval (CI) of 0.8 cm (-3.53 to 1.93). The placebo group also experienced increased pain in the quadriceps 96 h after the downhill run, with a mean VAS change ± 95% CI of -0.32 cm (-0.34 to 0.98).The serum concentration of IL-6 and TNF-α were significantly lower in the placebo group 24h after the downhill run. Mean IL-6 change ± 95% CI of 0.50 pg/mL (-1.59 to 0.59), and mean TNF-α change ± 95% CI was 0.98 pg/mL (-2.04 to 0.09). No other significant differences were identified between the groups for any other outcome measure. Considering all data from this study, P. notoginseng did not convincingly have an effect on performance, muscular pain or assessed blood markers in well-trained males after an intense bout of eccentric exercise that induced DOMS.

The effects of anatabine on non-invasive indicators of muscle damage: a randomized, double-blind, placebo-controlled, crossover study

BackgroundAnatabine (ANA), a minor tobacco alkaloid found in the Solanaceae family of plants, may exhibit anti-inflammatory activity, which may be useful to aid in recovery from exercise-induced muscle damage. The purpose of this study, therefore, was to examine the effects of ANA supplementation on the recovery of isometric strength and selected non-invasive indicators of muscle damage.MethodsA double-blinded, placebo-controlled, crossover design was used to study eighteen men (mean ± SD age = 22.2 ± 3.1 yrs; body mass = 80.3 ± 15.7 kg) who participated in two randomly-ordered conditions separated by a washout period. The ANA condition consisted of consuming 6–12 mg anatabine per day for 10 days, while testing took place during days 7–10. The placebo (PLA) condition was identical except that the PLA supplement contained no ANA. Maximal voluntary isometric peak torque (PT) of the forearm flexors, arm circumference, hanging joint angle, and subjective pain ratings were measured before (PRE), immediately after (POST), and 24, 48, and 72 h after six sets of 10 maximal, eccentric isokinetic forearm flexion muscle actions. Resting heart rate and blood pressure were measured at PRE and 72 h in each condition.ResultsFor PT, hanging joint angle, arm circumference, and subjective pain ratings, there were no condition x time (p > 0.05) interactions, there were no main effects for condition (p > 0.05), but there were main effects for time (p < 0.001). There were no condition x time (p > 0.05) interactions and no main effects for condition (p > 0.05) or time (p > 0.05) for blood pressure or resting heart rate.ConclusionsANA supplementation had no effect on the recovery of muscle strength, hanging joint angle, arm swelling, or subjective pain ratings after a bout of maximal eccentric exercise in the forearm flexors. Therefore, ANA may not be beneficial for those seeking to improve recovery from heavy eccentric exercise. Future studies should examine the effects of ANA on the pro-inflammatory cytokine responses to exercise-induced muscle damage and the chronic low-grade inflammation observed in obese and elderly individuals.

Microvascular Perfusion Changes in the Contralateral Gastrocnemius Following Unilateral Eccentric Exercise

Context: Eccentric exercise increases local blood flow and volume as a result of increased metabolic demand. It is not known how eccentric exercise affects microvascular perfusion in the musculature of the opposite limb over this 48 hour period. Objective: To quantify microvascular perfusion immediately after eccentric exercise to the gastrocnemius in the opposite limb and over 48 hours following the exercise. Design: Descriptive laboratory study. Setting: Laboratory. Patients or Other Participants: Six healthy participants volunteered (1M, 5F; Age: 22.4 ± 2.1 years; Height: 165.2 ± 16.6 cm; Weight: 64.5 ± 25.1 Kg). Intervention(s): A unilateral, eccentric exercise was performed to a randomized leg. Each subject performed 100 calf-lowering repetitions in the sequence of 50 repetitions, 5 min rest and 50 repetitions. Main outcome measure: Micro vascular perfusion measurements (blood volume (dB), blood flow (dB/sec), and blood flow velocity (1/sec)) of the contralateral gastrocnemius were taken using contrast-enhanced ultrasound (CEU) at baseline, immediately after exercise, and 48 hours after exercise. Pain using a visual analog scale was also recorded baseline, 24, and 48 hours after exercise to determine the onset of delayed onset muscle soreness (DOMS). Results: There was a significant increase in blood volume immediately after exercise (9.77 ± 3.19 dB) from baseline (6.18 ± 2.05 dB) (p=.023). There was a significant increase in blood flow immediately after exercise (3.53 ± 0.86 dB/sec) from baseline (2.40 ± 0.69 dB/sec) (p=.010). There was no change in blood flow velocity (p=0.487). Blood flow (p=0.003) and volume (p=0.002) remained significantly higher at 48 hours from baseline, with no change in blood flow velocity (p=0.316). Pain significantly increased. Conclusion: Micro vascular perfusion increased immediately after exercise in the contralateral gastrocnemius. This increase was maintained following a single bout of eccentric exercise over a 48 hour period in the presence of DOMS.

Elimination of Eccentric Exercise-Induced Interleukin-6 Response by Heat Preconditioning

Exercise training lowers the mortality rate of animals under heat stress. It is currently unknown whether heat preconditioning can attenuate exercise-induced increases in circulating interleukin-6 (IL-6) for athletes. Sixteen male basketball players were randomly assigned to the control (n = 8) and heat preconditioning (n = 8) groups. The heat preconditioning program consisted of a 30-min hot water immersion at 41°C performed every 72 h up to 4 sessions, which slightly elevated circulating creatine kinase (CK) and thiobarbituric acid-reactive substances (TBARS) by 27% and 21%, respectively (P ＜ 0.05). Seventy two hours after the last hot water immersion, both groups were challenged with an acute bout of eccentric exercise (6 squats at 85% maximal voluntary effort for 6 sets), which elicited significant increases in IL-6 (+120%) and CK (+34%) above pre-exercise level of the control group (P ＜ 0.05). This increase was absent in the heat preconditioning group. Heart rate variability (HRV) and high frequency power (HF) were increased following heat preconditioning, and remained elevated after exercise challenge. Our study provides evidence that eccentric exercise-induced stress response can be attenuated by a heat preconditioning protocol at 41°C.

Inflammatory markers CD11b, CD16, CD66b, CD68, myeloperoxidase and neutrophil elastase in eccentric exercised human skeletal muscles

The aim of the present study was to investigate leucocyte markers, CD11b, CD16, CD66b, CD68, myeloperoxidase and neutrophil elastase on skeletal muscle biopsies from biceps brachii after unaccustomed eccentric exercise followed by the second bout of exercise 3 weeks later. The subjects (10 subjects received COX-2 inhibitor (Celecoxib) and 13 subjects received placebo) were divided into three categories: mild, moderate and severe effect of eccentric exercise, according to the reduction and recovery of muscle force-generating capacity after performing 70 maximal eccentric actions with elbow flexors on an isokinetic dynamometer. The results showed that the CD66b antibody was applicable for localization of neutrophils in human skeletal muscle, whereas the other studied neutrophil markers recognized also other leucocytes than neutrophils. The number of CD66b positive cells in skeletal muscle was very low and was not affected by the exercise. The macrophage marker CD68 showed reactivity also against satellite cells and fibroblast-like cells in skeletal muscle and therefore cannot be applied as a quantitative value for inflammatory cells. Skeletal muscle fibre injury, shown as dystrophin negative fibres, was observed approximately in half of the biopsies at 4 and 7 days after the first exercise bout in the categories moderate and severe effect of eccentric exercise. These subjects represent the most prominent loss in muscle force-generating capacity both at the category and the individual levels. Furthermore, deformed skeletal muscle fibres were observed in five subjects in these categories after the second bout of exercise. The present results suggest that neutrophils are not involved in skeletal muscle fibre injury and the reduction in muscle force-generating capacity after a single bout of eccentric exercise is a good indirect indicator of muscle damage in humans. Furthermore, prolonged regeneration process could be one of the reasons for impaired peripheral muscle function after high-force eccentric exercise.

A single bout of eccentric exercise results in a type II muscle fiber specific increase in satellite cell content and activation status

Introduction: Satellite cells (SCs) are instrumental for repair, regeneration and growth of human skeletal muscle tissue. Following a single bout of exercise skeletal muscle SC can activate, proliferate and differentiate to form new SCs. In accordance, increases in mixed muscle SC content have been reported after 24–48h of recovery from a single bout of exercise. So far, little data exists on the fiber type-specific changes in SC content and activation status during post-exercise recovery. The present study investigates the impact of a single bout of eccentric exercise on skeletal muscle fiber type specific SC content and activation status following 24h of post-exercise recovery.

Concentrically trained cyclists are not more susceptible to eccentric exercise-induced muscle damage than are stretch–shortening exercise-trained runners

Here, we test the hypothesis that continuous concentric exercise training renders skeletal muscles more susceptible to damage in response to eccentric exercise. Elite road cyclists (CYC; n = 10, training experience 8.1 ± 2.0 years, age 22.9 ± 3.7 years), long-distance runners (LDR; n = 10, 9.9 ± 2.3 years, 24.4 ± 2.5 years), and healthy untrained (UT) men (n = 10; 22.4 ± 1.7 years) performed 100 submaximal eccentric contractions at constant angular velocity of 60° s(-1). Concentric isokinetic peak torque, isometric maximal voluntary contraction (MVC), and electrically induced knee extension torque were measured at baseline and immediately and 48 h after an eccentric exercise bout. Muscle soreness was assessed and plasma creatine kinase (CK) activity was measured at baseline and 48 h after exercise. Voluntary and electrically stimulated knee extension torque reduction were significantly greater (p < 0.05) in UT than in LDR and CYC. Immediately and 48 h after exercise, MVC decreased by 32 % and 20 % in UT, 20 % and 5 % in LDR, and 25 % and 6 % in CYC. Electrically induced 20 Hz torque decreased at the same times by 61 and 29 % in UT, 40 and 17 % in LDR, and 26 and 14 % in CYC. Muscle soreness and plasma CK activity 48 h after exercise did not differ significantly between athletes and UT subjects. In conclusion, even though elite endurance athletes are more resistant to eccentric exercise-induced muscle damage than are UT people, stretch-shortening exercise-trained LDR have no advantage over concentrically trained CYC.

Specific training improves skeletal muscle mitochondrial calcium homeostasis after eccentric exercise

There is limited understanding of the mitochondrial adaptation following repeated eccentric exercise bouts, a model resulting in muscle adaptation known as the repeat bout effect. It was hypothesized that downhill training would reduce mitochondrial calcium content (MCC) post an acute eccentric bout with concurrent improvements in mitochondrial respiratory function. Thirty-four Sprague-Dawley rats were divided into four groups: control (N), control with acute eccentric exercise (N (ecc)), trained control (X) and trained with acute eccentric exercise (X (ecc)). Training for X and X (ecc) consisted of 30min per day for five consecutive days of downhill treadmill running. The acute eccentric exercise bout was a -14° treadmill exercise for 90min performed 2weeks after the training period. Animals were killed 48h post-exercise. Isolated mitochondria from the red quadriceps allowed for the measure of mitochondrial respiratory indices and MCC. Calpain activity and heat shock protein 72 expression (HSP72) were also measured. MCC dramatically increased following the acute bout of eccentric exercise in N (ecc) (p<0.001), but did not change in X (ecc). Mitochondrial respiratory function tended to be slightly depressed in N (ecc) (state 3 respiration, p=0.053; respiratory control ratio, p=0.098) and unaltered in X (ecc). Previous training altered the calpain and heat shock protein response to an acute bout of eccentric exercise. The results suggest that downhill exercise training improves mitochondrial calcium homeostasis following an acute bout of prolonged eccentric exercise and may stabilize mitochondrial respiratory function. These improvements coincide with a reduction in calpain activity and heat shock protein upregulation.

Dose-dependency of massage-like compressive loading on recovery of active muscle properties following eccentric exercise: rabbit study with clinical relevance

BackgroundOptimal strategies for massage and its use in athletes have not been conclusively demonstrated.Purpose/study designEffects of varying duration, frequency and magnitude of massage-like compressive loading (MLL) on recovery of skeletal...

P01.42. Dose-dependent effects of massage-like loading in an animal model following eccentric exercise

Methods Twenty-four New Zealand white rabbits were surgically instrumented and underwent a bout of damaging eccentric exercise to the tibialis anterior muscle. Rabbits were randomly assigned to a protocol with massage frequency of 0.25 or 0.50Hz at a compressive force of 5 or 10N for 15 or 30 minutes. The contralateral limb served as the exercised, non-massaged control. A torque-angle relationship was obtained for 21 tibiotarsal joint angles, preand post-exercise, and post four consecutive days of massage (applied by customized device). Peak isometric torque was the primary outcome variable. Muscle wet weight and histological analysis were also performed at the end of the protocol.

Sensory Mapping of the Upper Trapezius Muscle in Relation to Consecutive Sessions of Eccentric Exercise

The aim of this study was to evaluate the changes in pressure pain sensitivity maps in untrained subjects over 2 subsequent sessions of eccentric exercise (ECC) expected to result in (a) delayed onset muscle soreness (DOMS) and (b) adaptation/recovery, respectively. Eleven healthy male subjects participated in this study. Pressure pain threshold (PPT), rate of perceived exertion (RPE), pain intensity, soreness area drawing, maximal voluntary contraction (MVC), and shoulder range of motion were assessed in session 1 before, immediately after, and 24 hours after ECC. The ECC protocol that was used to induce DOMS consisted of 50 eccentric contractions of the right shoulder that were divided into 5 bouts, including 10 contractions at MVC level separated by a 2-minute resting period. Session 2 was identical to session 1 and performed exactly 1 week later. There was only a significant increase in the RPE assessed before the exercise and 24 hours after the exercise in session 1 (p = 0.001). The average PPT only decreased significantly from before the exercise (660.2 ± 76.2 kPa) to 24 hours after the exercise (435.6 ± 59.3 kPa) in session 1 (p = 0.016). The present study confirmed a heterogeneous distribution of mechanical sensitivity before and after sessions of ECC. The first session of ECC underlined increased mechanical sensitivity because of DOMS, whereas the second session reflected an adaptation process. Our results support the potential role of ECC bouts in training regimens.

Diffusion tensor MRI to assess skeletal muscle disruption following eccentric exercise

Structural evidence of exercise-induced muscle disruption has traditionally involved histological analysis of muscle tissue obtained by needle biopsy, however, there are multiple limitations with this technique. Recently, diffusion tensor magnetic resonance imaging (DT-MRI) has been successfully demonstrated to noninvasively assess skeletal muscle abnormalities induced by traumatic injury. To determine the potential for DT-MRI to detect musculoskeletal changes after a bout of eccentric exercise, 10 healthy men performed 300 eccentric actions on an isokinetic dynamometer. DT-MRI measurements and muscle biopsies from the vastus lateralis were obtained before and 24 h post-exercise. Z-band streaming was higher 24 h post-exercise compared with baseline (P < 0.05). The histological indices of damage coincided with changes in DT-MRI parameters of fractional anisotropy (FA) and apparent diffusion coefficient; reflecting altered skeletal muscle geometry (P < 0.05). Z-band streaming quantified per fiber correlated with FA (r = -0.512; P < 0.05). DT-MRI can detect changes in human skeletal muscle structure following eccentric exercise.

Establishment of an animal model for delayed-onset muscle soreness after high-intensity eccentric exercise and its application for investigating the efficacy of low-load eccentric training

BackgroundDelayed-onset muscle soreness (DOMS) occurs after unaccustomed exercise and is particularly associated with eccentric exercise. Previous studies have proposed the use of a single bout of eccentric exercise to prevent the muscle damage subsequent to a bout of eccentric exercise. This study aimed to establish a suitable animal model to evaluate the pain in DOMS and to assess whether low-load eccentric training confers a protective effect against a subsequent high-intensity eccentric exercise bout. MethodsThirty-six female Wistar rats were divided into five groups: rats that received muscular compression only (Comp); those that received high-intensity eccentric exercise only (HE); those that received muscular compression at 3, 24, 48, and 96h after high-intensity eccentric exercise (HE + Comp/3, 24, 48, and 96h); those that received muscular compression 48h after a single low-load eccentric exercise (LE); and those that received a week of low-load eccentric training before high-intensity eccentric exercise, which was followed by muscular compression 48h later (LET). Immunohistochemistry was used to investigate c-fos expression in the dorsal horn of the spinal cord. ResultsFor the HE + Comp/48h rats, the total number of c-fos-positive neurons at the L2–3 segments was significantly greater than that in the Comp and HE rats in the same segments. A week of low-load eccentric training resulted in a decreased number of c-fos-ir neurons relative to that in the HE + Comp/48h rats. ConclusionsMuscle tenderness after high-intensity eccentric exercise was evaluated by c-fos expression in the dorsal horn of the rat spinal cord. Using this rat model, the present study clarified that the muscle tenderness following high-intensity eccentric exercise is inhibited by prior low-load eccentric training.

Hormone Therapy and Maximal Eccentric Exercise Alters Myostatin-Related Gene Expression in Postmenopausal Women

We sought to evaluate baseline mRNA values and changes in gene expression of myostatin-related factors in postmenopausal women taking hormone therapy (HT) and not taking HT after eccentric exercise. Fourteen postmenopausal women participated including 6 controls not using HT (59 ± 4 years, 63 ± 17 kg) and 8 women using HT (59 ± 4 years, 89 ± 24 kg). The participants performed 10 sets of 10 maximal eccentric repetitions of single-leg extension on a dynamometer. Muscle biopsies from the vastus lateralis were obtained from the exercised leg at baseline and 4 hours after the exercise bout. Gene expression was determined using reverse transcriptase polymerase chain reaction for myostatin, activin receptor IIb (ActRIIb), follistatin, follistatin-related gene (FLRG), follistatin-like-3 (FSTL3), and GDF serum-associated protein-1 (GASP-1). In response to the exercise bout, myostatin and ActRIIb significantly decreased (p < 0.05), and follistatin, FLRG, FSTL3, and GASP-1 significantly increased in both groups (p < 0.05). Significantly greater changes in gene expression of all genes occurred in the HT group than in the control group after the acute eccentric exercise bout (p < 0.05). These data suggest that postmenopausal women using HT express greater myostatin-related gene expression, which may reflect a mechanism by which estrogen influences the preservation of muscle mass. Further, postmenopausal women using HT experienced a profoundly greater myostatin-related response to maximal eccentric exercise.

Effect of docosahexaenoic acid (DHA) ingestion on muscle damage response to resistance exercise and training

Muscle damage and soreness may discourage resistance exercise participation. Our purpose was to determine if DHA ingestion affects the muscle damage response to: 1. acute eccentric exercise, 2. initiation of a subsequent resistance training program. Forty‐one healthy, untrained young adult male subjects consumed DHA (2 g/d) or placebo for 28 d before an eccentric exercise bout with the non‐dominant arm (six sets of 10 using 140% 1RM) on day 1. Subjects continued supplementation and began a multiple‐exercise resistance training program on day 4 and continued 3 d per week through d 17. Muscle damage was assessed using maximal isometric muscle force, delayed onset muscle soreness (DOMS, 100 mm scale), range of motion (ROM) and serum CK (analyzed as log) on days 1, 2, 3, 4, 7, 12, 17. The acute response to eccentric exercise (day 1–4) was reduced muscle strength (32.9%) and ROM (16%) and increased DOMS (32 mm) and CK to 3713 U/L. DHA lowered the overall CK response (p= 0.045) but did not influence the response of other factors to the acute bout. When all time points were analyzed, DHA did not influence muscle strength or ROM response but tended to dampen CK (p = 0.058) and DOMS (p = 0.086) over the 17 days. In summary, DHA reduced a marker of muscle damage following acute eccentric exercise and tended to dampen this marker and soreness during the initial period of resistance training. Funded by a grant from Martek Biosciences Corporation.