Single Bout Of Eccentric Exercise Research Articles

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.

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.

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.

Eccentric Exercise Facilitates Mesenchymal Stem Cell Appearance in Skeletal Muscle

Eccentric, or lengthening, contractions result in injury and subsequently stimulate the activation and proliferation of satellite stem cells which are important for skeletal muscle regeneration. The discovery of alternative myogenic progenitors in skeletal muscle raises the question as to whether stem cells other than satellite cells accumulate in muscle in response to exercise and contribute to post-exercise repair and/or growth. In this study, stem cell antigen-1 (Sca-1) positive, non-hematopoetic (CD45-) cells were evaluated in wild type (WT) and α7 integrin transgenic (α7Tg) mouse muscle, which is resistant to injury yet liable to strain, 24 hr following a single bout of eccentric exercise. Sca-1+CD45− stem cells were increased 2-fold in WT muscle post-exercise. The α7 integrin regulated the presence of Sca-1+ cells, with expansion occurring in α7Tg muscle and minimal cells present in muscle lacking the α7 integrin. Sca-1+CD45− cells isolated from α7Tg muscle following exercise were characterized as mesenchymal-like stem cells (mMSCs), predominantly pericytes. In vitro multiaxial strain upregulated mMSC stem cells markers in the presence of laminin, but not gelatin, identifying a potential mechanistic basis for the accumulation of these cells in muscle following exercise. Transplantation of DiI-labeled mMSCs into WT muscle increased Pax7+ cells and facilitated formation of eMHC+DiI− fibers. This study provides the first demonstration that mMSCs rapidly appear in skeletal muscle in an α7 integrin dependent manner post-exercise, revealing an early event that may be necessary for effective repair and/or growth following exercise. The results from this study also support a role for the α7 integrin and/or mMSCs in molecular- and cellular-based therapeutic strategies that can effectively combat disuse muscle atrophy.

Effects of 14 days of prophylactic resveratrol supplementation in trained endurance runners upon the inflammatory markers TNF-a, IL1β, and IL-6 following a single bout of eccentric exercise

Background Resveratrolis a natural polyphenol found in peanuts and grapes. Resveratrolpossesses antioxidative properties which have shown to reduce the oxidative damage from reactive oxygen species (ROS). Resveratrol also has the ability to attenuate inflammation via inhibiting TNF-a, IL-1b, IL-6, and blocking NF-kB activation. Resveratrol supplementation may have the potential to mitigate the damages associated with intense orprolonged exercise; consequently improving recovery. The purpose of this study is to evaluate the effects of a14 day prophylactic supplementation trans-resveratrol onTNF-a, IL-1b ,a nd IL-6 from a single bout of eccentric exercise in traineddistance runners. Methods Eight trained male distance runners ages 35 to 45 (38.13 ± 2.95yrs) were randomly assigned to consume in a double blind manner either a placebo (PL) or 1000mg of transresveratrol (polygonum cuspidatum)(RESV) daily for 14 days (Transmax, BiotiviaBioceuticals). Prior to supplementation participants’ height (69.5 ± 2.3in) and weight (165.2 ± 24.25lbs.) were recorded and body composition (17.75 ± 4.8BF%) was assessed using DEXA. VO2max (55.3 ± 6.4 ml/kg/min) was assessed using Fox and Costill protocol and 65% of VO2max heart rate (117±4.2 bpm) was established for use as intensity predicator in the downhill running protocol. Following 14 days of prophylactic supplementation, participants engaged in a 45 minute downhill running protocol at 65% of VO2max at a declined grade of 12%. Venous blood samples were taken prior to (PRE), immediately after(POST), one hour (1HR) and two hours (2HR) following the downhill protocol. Serum samples for each time point (PRE,POST, 1HR, 2HR) were assayed for TNF-a, IL-1b ,a nd IL-6 using ELISA. Dietary analyses were conducted during the four days prior to testing to determine any antioxidant and anti-inflammatory influences within the diet. Results A significant main effect for time (p = 0.003) for IL-6 (RESV: 0.613±0.253, 1.38±0.394, 1.978±0.479, 1.594±0.66; PL: 0.921±0.73, 2.25±1.05, 1.698±0.561, 1.953±1.87 pg/mL). Delta responses for IL-6 showed a 125.12% change at POST, 222.68% change at 1HR, and 160.03% at 2HR for the RESV group while the PL group showed a 144.3%, 84.36%, and 112.05% change at the same time points, respectively. No significant observationsfor time or between groups for TNF-a and IL-1b were observed. Responsefrom baseline for TNF-a showed a 10.91% change at POST, 53.33% change at 1HR, and 8.48% at 2HR for the RESV group while the PL group showed a 15.3%, -1.87%, and -8.96% change at the same time points (p > 0.05), respectively. For IL-1b, the response from baseline showed a 10.96% change at POST, 16.04% change at 1HR, and 18.18% at 2HR for the RESV group while the PL group showed a -39.67%, -31.15%, and -33.93% change at the same time points (p >0 .05), respectively.No differences were observed on pain scale values between groups resulting from the eccentric protocol (p > 0.05).

The α7β1-integrin accelerates fiber hypertrophy and myogenesis following a single bout of eccentric exercise

The α(7)β(1)-integrin is a heterodimeric transmembrane protein that adheres to laminin in the extracellular matrix, representing a critical link that maintains structure in skeletal muscle. In addition to preventing exercise-induced skeletal muscle injury, the α(7)-integrin has been proposed to act as an intrinsic mechanosensor, initiating cellular growth in response to mechanical strain. The purpose of this study was to determine the extent to which the α(7)-integrin regulates muscle hypertrophy following eccentric exercise. Wild-type (WT) and α(7)-integrin transgenic (α(7)Tg) mice completed a single bout of downhill running exercise (-20°, 17 m/min, 60 min), and gastrocnemius-soleus complexes were collected 1, 2, 4, and 7 days (D) postexercise (PE). Maximal isometric force was maintained and macrophage accumulation was suppressed in α(7)Tg muscle 1D PE. Mean fiber cross-sectional area was unaltered in WT mice but increased 40% in α(7)Tg mice 7D PE. In addition, a rapid and striking fivefold increase in embryonic myosin heavy chain-positive fibers appeared in α(7)Tg mice 2D PE. Although Pax7-positive satellite cells were increased in α(7)Tg muscle 1D PE, the number of nuclei per myofiber was not altered 7D PE. Phosphorylation of mammalian target of rapamycin (mTOR) was significantly elevated in α(7)Tg 1D PE. This study provides the first demonstration that the presence of the α(7)β(1)-integrin in skeletal muscle increases fiber hypertrophy and new fiber synthesis in the early time course following a single bout of eccentric exercise. Further studies are necessary to elucidate the precise mechanism by which the α(7)-integrin can enhance muscle hypertrophy following exercise.

The Influence Of An Acute Bout Of Eccentric Exercise On The Hamstrings To Quadriceps Ratio

INTRODUCTION: The hamstrings to-quadriceps (H:Q) ratio has been used to assess the muscle balance at the knee joint. An imbalance of the flexor and extensor muscles at the knee joint has been shown to be associated with an increased risk for knee and hamstring related injuries. Eccentric training may potentially influence the (H:Q) ratio as it leads to an acute reduction in muscle force and impaired muscle function in the days following the workout. However, we are aware of no previous studies that have examined the effects of an acute bout of eccentric exercise on the H:Q ratio. PURPOSE: To examine the effects of a single bout of eccentric exercise on the H:Q ratio in recreationally active college age males. METHODS: Eight healthy male individuals (mean ± age = 20.75 ± 2.49 yr) volunteered to participate in the study. Isokinetic peak torque (IPT) of the right leg extensors and flexors were assessed on a Biodex System 2 dynamometer at 60° s-1. IPT was assessed 4 days prior to the eccentric workout protocol and again 24 hrs following the protocol. The eccentric workout consisted of four sets of 10 repetitions for the leg press, leg extension, and leg curl exercises that were performed at 120% of their predetermined concentric one repetition maximum. All exercises were performed on the right leg only. Conventional H:Q ratios were calculated by dividing the highest leg flexion IPT value by the highest leg extension IPT value. A paired samples t-test was used to analyze all data. An alpha of P ≤ 0.05 was used to determine statistical significance. RESULTS: The acute bout of eccentric exercise resulted in a significant decrease in IPT of the leg extensors (-10.93%, P = 0.007) and a non-significant decrease in IPT of the leg flexors (-5.90%, P = 0.138) at 24 hrs post eccentric training. There was no significant difference (P = 0.302) observed in the H:Q ratio following the acute eccentric exercise protocol. CONCLUSIONS: These findings indicated that a single bout of eccentric exercise reduced hamstring and quadriceps isokinetic strength, but did not influence the H:Q ratio. Thus, an acute bout of lower body eccentric exercise appears to not adversely affect muscular balance across the knee joint as measured from the H:Q ratio.

The α7B1 Integrin Promotes Skeletal Muscle Hypertrophy Following Eccentric Exercise

Myogenesis and/or new and preexisting fiber hypertrophy are primary factors responsible for muscle growth observed following eccentric exercise training. We have recently demonstrated that muscle-specific transgenic expression of the α7 integrin enhances de novo fiber synthesis in skeletal muscle following a single bout of eccentric exercise. PURPOSE: The purpose of this study was to determine the extent to which transgenic expression of the α7 integrin increases muscle fiber size and force generation following multiple bouts of eccentric exercise. METHODS: 5 wk old, female wild type (WT) (n=10) and α7BX2 integrin transgenic (α7Tg) (n=10) mice were randomly assigned to one of two groups: 1) sedentary (SED) or 2) exercise training (EX). Exercise training consisted of downhill running 3 times/wk for 4 wk (-20°, 17 m/min, 30 min). Twenty-four hr following the final training session, maximal isometric hindlimb plantarflexor force was measured via in situ stimulation of the sciatic nerve. Gastrocnemius-soleus complexes were collected for further analysis of fiber cross sectional areas (CSA). Analysis of signaling events reflective of protein synthesis (AKT and p70S6K) were completed on the contralateral limb. RESULTS: Whereas p70S6K phosphorylation was elevated 1.5-fold (P<0.05), no significant increases in average CSA (WT SED: 617.02 56.34 vs. WT EX: 847.77 76.18 mm2; NS), or hindlimb force were observed in the WT EX group compared to WT SED. In contrast, all AKT, mTOR and p70S6K phosphorylation were significantly elevated (AKT: 70%, mTOR: 2.0-fold; p70S6K: 1.3-fold; P<0.05) and concomitant increases in average CSA (α7Tg SED: 1280.80 62.25 mm2 vs. α7Tg EX: 1790.25 126.88; P<0.05) and hindlimb force (25.3%; P=0.054) were observed in the α7Tg EX group compared to α7Tg SED. The percentage of fibers ranging 2000 to 3000 mm2 increased 2.6-fold in α7Tg EX compared to α7Tg SED (P<0.05). CONCLUSION: The results from this study and our previous work demonstrate that the presence of the α7 integrin markedly enhances individual muscle fiber growth and suggest the α7B1 integrin is an important regulator of exercise-induced hypertrophy. Supported by grants from the Illinois Regenerative Medicine Institute, UIUC Arnold O. Beckman Award, and the Ellison Medical Foundation.

Calpains, skeletal muscle function and exercise

1. Skeletal muscle fibres contain ubiquitous (mu-calpain and m-calpain) and muscle-specific (calpain-3) Ca(2+)-dependent proteases. The physiological roles of the calpains are not well understood, although ubiquitous calpains have been associated with apoptosis and myogenesis and calpain-3 is likely involved in sarcomeric remodelling. A defect in the expression of calpain-3 results in limb-girdle muscular dystrophy Type 2A. 2. At resting [Ca(2+)](i), calpains are present predominantly in their full-length, unautolysed/unactivated forms. Once activated, mu-calpain and calpain-3 appear in their autolysed forms and this measurement can be used to determine when in vivo activation occurs. Endogenously expressed mu-calpain and calpain-3 are activated within a physiological [Ca(2+)] range in a Ca(2+)- and time-dependent manner. 3. In skeletal muscle, mu-calpain is a freely diffusible protein that binds rapidly when [Ca(2+)](i) is increased. Calpain-3 is tightly bound in skeletal muscle fibres at the N2A line of the large elastic protein titin. 4. Overall, neither mu-calpain nor calpain-3 are activated immediately following sprint, endurance or eccentric exercise, despite the frequent episodes of high cytoplasmic [Ca(2+)] that would occur during these types of muscle contractions. Importantly, however, a substantial proportion of calpain-3, but not mu-calpain, is activated 24 h after a single bout of eccentric exercise. 5. In vitro studies have shown that calpain-3 becomes activated if exposed for a prolonged period of time (> 1 h) to resting cytoplasmic [Ca(2+)] that are approximately two- to fourfold higher than normal. This suggests that the small but sustained increase in [Ca(2+)](i) that likely occurs after eccentric contractions is both high and long enough to result in calpain-3 activation and supports the role for calpain-3 in sarcomeric remodelling.

Calpain-3 is activated following eccentric exercise

LETTERS TO THE EDITORCalpain-3 is activated following eccentric exerciseRobyn M. Murphy and Graham D. LambRobyn M. Murphy and Graham D. LambDepartment of Zoology, La Trobe University, Melbourne, Victoria, AustraliaPublished Online:01 Jun 2009https://doi.org/10.1152/japplphysiol.00239.2009MoreSectionsPDF (28 KB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations to the editor: In a recent article by Lehti et al. (3) the effect of fatiguing exercise on the mRNA expression of a number of skeletal muscle proteins was examined. In the discussion it was stated that in a study conducted by our laboratory, calpain-3 mRNA was increased 24 h after a bout of eccentric exercise (4). It needs to be pointed out that this was NOT a finding in that manuscript and there were no mRNA measurements made in that study. We in fact measured calpain-3 protein and reported the first physiological activation of calpain-3, which occurred 24 h after the single bout of eccentric exercise in humans. These findings support a role for calpain-3 in sarcomeric remodeling following eccentric exercise. We used autolysis as a measure of calpain-3 activity because it is known that calpain-3 must be autolysed for it to become activated (2). Recently, we (5) showed that calpain-3 is activated when in the presence of only ∼200 nM Ca2+ for 1 h, although it was not activated over the same period of time in the presence of ∼50 nM Ca2+.The finding of no change or as stated “a decreasing trend in calpain-3 mRNA expression was seen” 2 days after the exercise protocol (3) is similar to that previously reported following eccentric exercise (1). In the latter study, the authors pointed out that mRNA measurements are not necessarily indicative of enzyme activity and protein levels, although some correlation between the mRNA and protein levels for m-calpain has been reported (6). There is no evidence for such associations among mRNA, protein levels, or protein activity for the skeletal muscle specific calpain-3. The previous findings (1, 3, 4) might suggest that there is indeed no correlation between calpain-3 mRNA and protein levels and that if knowledge is to be obtained about the functional role of calpain-3 in skeletal muscle then autolysis of the full-length endogenously expressed protein needs to be measured.REFERENCES1 Feasson L, Stockholm D, Freyssenet D, Richard I, Duguez S, Beckmann JS, Denis C. Molecular adaptations of neuromuscular disease-associated proteins in response to eccentric exercise in human skeletal muscle. J Physiol 543: 297–306, 2002.Crossref | PubMed | ISI | Google Scholar2 Garcia Diaz BE, Moldoveanu T, Kuiper MJ, Campbell RL, Davies PL. Insertion sequence 1 of muscle-specific calpain, p94, acts as an internal propeptide. J Biol Chem 279: 27656–27666, 2004.Crossref | PubMed | ISI | Google Scholar3 Lehti M, Kivela R, Komi PV, Komulainen J, Kainulainen H, Kyrolainen H. Effects of fatiguing jumping exercise on mRNA expression of titin-complex proteins and calpains. J Appl Physiol 106: 1419–1424, 2009.Link | ISI | Google Scholar4 Murphy RM, Goodman CA, McKenna MJ, Bennie J, Leikis M, Lamb GD. Calpain-3 is autolyzed and hence activated in human skeletal muscle 24 h following a single bout of eccentric exercise. J Appl Physiol 103, 926–931, 2007.Link | ISI | Google Scholar5 Murphy RM, Lamb GD. Endogenous calpain-3 activation is primarily governed by small increases in resting cytoplasmic [Ca2+] and is not dependent on stretch. J Biol Chem 284: 7811–7819, 2009.Crossref | PubMed | ISI | Google Scholar6 Spencer MJ, Lu B, Tidball JG. Calpain II expression is increased by changes in mechanical loading of muscle in vivo. J Cell Biochem 64: 55–66, 1997.Crossref | PubMed | ISI | Google ScholarAUTHOR NOTESAddress for reprint requests and other correspondence: R. M. Murphy, Dept. of Zoology, La Trobe Univ., Melbourne, Victoria, 3086 Australia (e-mail: [email protected]) Download PDF Previous Back to Top Next FiguresReferencesRelatedInformation Cited ByDoes Obesity Affect the Severity of Exercise-Induced Muscle Injury?Journal of Obesity & Metabolic Syndrome, Vol. 30, No. 2Insertion sequence 1 from calpain-3 is functional in calpain-2 as an internal propeptideJournal of Biological Chemistry, Vol. 293, No. 46Calpain-3-mediated regulation of the Na+-Ca2+ exchanger isoform 327 October 2015 | Pflügers Archiv - European Journal of Physiology, Vol. 468, No. 2SERCA1 overexpression minimizes skeletal muscle damage in dystrophic mouse modelsDavi A. G. Mázala, Stephen J. P. Pratt, Dapeng Chen, Jeffery D. Molkentin, Richard M. Lovering, and Eva R. Chin1 May 2015 | American Journal of Physiology-Cell Physiology, Vol. 308, No. 9Calpains, skeletal muscle function and exerciseClinical and Experimental Pharmacology and Physiology, Vol. 37, No. 3Reply to Murphy and LambMaarit Lehti, Riikka Kivelä, Paavo Komi, Jyrki Komulainen, Heikki Kainulainen, and Heikki Kyröläinen1 June 2009 | Journal of Applied Physiology, Vol. 106, No. 6 More from this issue > Volume 106Issue 6June 2009Pages 2068-2068 Copyright & PermissionsCopyright © 2009 the American Physiological Societyhttps://doi.org/10.1152/japplphysiol.00239.2009PubMed19470844History Published online 1 June 2009 Published in print 1 June 2009 Metrics

Reply to Murphy and Lamb

LETTERS TO THE EDITORReply to Murphy and LambMaarit Lehti, Riikka Kivelä, Paavo Komi, Jyrki Komulainen, Heikki Kainulainen, and Heikki KyröläinenMaarit Lehti, Riikka Kivelä, Paavo Komi, Jyrki Komulainen, Heikki Kainulainen, and Heikki KyröläinenPublished Online:01 Jun 2009https://doi.org/10.1152/japplphysiol.00322.2009MoreSectionsPDF (24 KB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInEmail to the editor: In their letter to the editor, Dr. Murphy and Dr. Lamb (3) address the erroneous citation of their article (2) in our paper (1) and highlight the importance of posttranscriptional regulation of calpain-3. The remark of Dr. Murphy and Dr. Lamb is justified. As a result of an unfortunate mistake, which occurred at the finishing and shortening phase of the discussion, factual content of text and reference (2) became erroneous. We apologize for the incident. Fortunately, the mistake did not change the essential content of our article.REFERENCES1 Lehti M, Kivela R, Komi PV, Komulainen J, Kainulainen H, Kyrolainen H. Effects of fatiguing jumping exercise on mRNA expression of titin-complex proteins and calpains. J Appl Physiol 106: 1419–1424, 2009.Link | ISI | Google Scholar2 Murphy RM, Goodman CA, McKenna MJ, Bennie J, Leikis M, Lamb GD. Calpain-3 is autolyzed and hence activated in human skeletal muscle 24 h following a single bout of eccentric exercise. J Appl Physiol 103, 926–931, 2007.Link | ISI | Google Scholar3 Murphy RM, Lamb GD. Calpain-3 is activated following eccentric exercise. J Appl Physiol; doi:10.1152/japplphysiol.00239.2009.Link | ISI | Google Scholar Previous Back to Top FiguresReferencesRelatedInformation More from this issue > Volume 106Issue 6June 2009Pages 2069-2069 Copyright & PermissionsCopyright © 2009 the American Physiological Societyhttps://doi.org/10.1152/japplphysiol.00322.2009History Published online 1 June 2009 Published in print 1 June 2009 PDF download Metrics Downloaded 94 times

Impact of repeated bouts of eccentric exercise on sarcolemma disruption in human skeletal muscle

In animal models, unaccustomed eccentric exercise (EE) has been widely related to muscle fiber membrane (sarcolemma) damage. On the contrary, studies in humans reported that sarcolemma was not susceptible to damage following a single bout of EE. We hypothesized that the single bout of EE used by those studies was not sufficient to induce sarcolemma damage, in humans. In this study we examined muscle biopsies from untrained males who either performed six sets of 15 reps of maximum voluntary eccentric contractions (n=9), for six consecutive days, or served as control-group (n=6). Blood and biopsy samples were obtained one week prior to exercise, immediately after bout 3, and 24h after the last training session. In addition to standard haematoxylin-eosin staining, all biopsies were stained immunohistochemically using antibodies specific for fibronectin and desmin antigens. In the exercise-group, no biopsies taken at pre-exercise or post-exercise level showed evidence of sarcolemma damage as stained by anti-fibronectin antibody in eight of nine subjects. Serum creatine kinase (CK) and lactate dehydrogenase (LDH) activities increased significantly throughout the study despite the lack of sarcolemma damage.We suggest that in humans, repeated bouts of EE do not cause gross sarcolemma damage in the mid-belly of Vastus Lateralis.

Calpain-3 is autolyzed and hence activated in human skeletal muscle 24 h following a single bout of eccentric exercise

The function and normal regulation of calpain-3, a muscle-specific Ca(2+)-dependent protease, is uncertain, although its absence leads to limb-girdle muscular dystrophy type 2A. This study examined the effect of eccentric exercise on calpain-3 autolytic activation, because such exercise is known to damage sarcomeric structures and to trigger adaptive changes that help prevent such damage on subsequent exercise. Six healthy human subjects performed a 30-min bout of one-legged, eccentric, knee extensor exercise. Torque measurements, vastus lateralis muscle biopsies, and venous blood samples were taken before and up to 7 days following the exercise. Peak isometric muscle torque was depressed immediately and at 3 h postexercise and recovered by 24 h, and serum creatine kinase concentration peaked at 24 h postexercise. The amount of autolyzed calpain-3 was unchanged immediately and 3 h after exercise, but increased markedly (from approximately 16% to approximately 35% of total) 24 h after the exercise, and returned to preexercise levels within 7 days. In contrast, the eccentric exercise produced little autolytic activation of the ubiquitous Ca(2+)-activated protease, mu-calpain. Eccentric exercise is the first physiological circumstance shown to result in calpain-3 activation in vivo.

Effects of Eccentric Exercise on Passive Mechanical Properties of Human Gastrocnemius in vivo

In this study, we used a newly developed method for measuring passive length-tension relations of a single human muscle in vivo to quantify changes in the mechanical properties of the human gastrocnemius after eccentric exercise. Twelve subjects performed eccentric exercise on the right leg for 1 h by walking backward downhill on a treadmill. Passive ankle torque was measured as the ankle was rotated within its available range, with the knee in eight different angles. Subjects were studied before exercise, 1 h after exercise, and 24 h later, with further measurements at 48 h and at 1 wk in a subset of six subjects. Subjects also rated the level of perceived muscle soreness on a 10-point scale during walking on flat ground. We examined passive tension in the gastrocnemius at a standard length before and at various times after exercise. Muscle tension increased significantly at this length 1 h after exercise (34.7 +/- 7.3%; mean +/-SEM), peaked at 24 h (88.4 +/- 12.6%), declined at 48 h (45.5 +/- 4.4%), and returned to the control level at 1 wk. Stiffness of the gastrocnemius in the sitting and standing postures (i.e., at short and long lengths) was derived from passive length-tension relations. Stiffness increased after exercise, and the relative changes in muscle stiffness were similar in both positions. There was no apparent correlation between stiffness and subjective reports of muscle soreness during walking. This study provides the first specific measurements of the increase in stiffness of the human gastrocnemius in vivo after a single bout of eccentric exercise. The increase peaks at 24 h and is nearly fully resolved within 1 wk.

Estradiol Attenuates Oxidative Stress, Skeletal Muscle Apoptosis, and Exercise-Induced Muscle Injury in Females

PURPOSE: 17β-estradiol possesses anti-oxidant properties which may provide protection against the associated effects of exercise-induced muscle injury. This study's purpose was to determine if an estrogenic protective mechanism exists between genders for skeletal muscle oxidative stress, apoptosis, and muscle injury resulting from eccentric muscle contractions. METHODS: Eight males and eight females performed 7 sets of 10 eccentric repetitions at 150% 1RM of the knee extensors on the same day that corresponded to the mid-luteal (days 21–23) phase of each female's menstrual cycle. Blood and muscle biopsy samples were obtained prior to exercise and 6 and 24 h post-exercise, while additional blood samples were obtained at 48 and 72 h post-exercise. Knee extensor strength and perceived muscle soreness were determined at 6, 24, 48 and 72 h post-exercise. Blood samples were assayed for 17β-estradiol and oxidative stress markers (superoxide dismutase and 8-isoprostane) using EIA. Muscle samples were used to determine markers of mitochondrial apoptosis (bax, bcl-2, cytochrome-c) and cell death using ELISA. Myofibrillar protein and total DNA content were determined at OD595 and OD260, respectively. RESULTS: Knee extensor strength decreases were significantly greater in males than females (p <0.001) and peaked at 24 h post-exercise. Males reported greater (p <0.001) readings of muscle soreness that peaked at 24 h post-exercise. Females had greater estrogen levels throughout all time points (p < 0.001). Females had higher (p <0.001) levels of serum superoxide dismutase compared to males, while 8-isoprostane levels were higher (p 0.05). Cell death increased in males at 24h post-exercise (p0.05). Myofibrillar protein content was similar between genders but significantly decreased (p = 0.047) at 24 h post-exercise. Decreases in total DNA content were greater for males (p <0.05) and peaked at 24 h post-exercise compared to pre-exercise. CONCLUSIONS: As a result of its anti-oxidant properties and elevated levels in females, 17β-estradiol appears to reduce levels of oxidative stress, which may in fact attenuate apoptosis and muscle injury in response to a single bout of eccentric exercise otherwise observed in males.

Attenuation of Protective Effect Against Eccentric Exercise-Induced Muscle Damage

A single bout of eccentric exercise confers a long-lasting protective effect against subsequent bouts of the same exercise. This study investigated how the protective effect was lessened when the interval between the initial and secondary exercise bouts was increased from 4 to 12 weeks. Thirty young men performed two bouts of 12 maximal eccentric actions of the elbow flexors of the nondominant arm separated by either 4 (n = 9), 8 (n = 10), or 12 (n = 11) weeks. Maximal isometric strength, flexed and relaxed elbow joint angles, range of motion, upper arm circumference, muscle soreness, plasma creatine kinase (CK), and myoglobin (Mb) were measured before, immediately after, and for 4 days after exercise. Changes in criterion measures were compared between bouts for each group and among groups by two-way repeated-measures ANOVA. There were no significant differences among groups in the changes in all measures following the first bout. Significantly (p < 0.05) smaller responses in all measures were observed after the second bout as compared with first bout for the 4 and 8 weeks, but only in strength, muscle soreness, CK, and Mb for the 12 weeks. It was concluded that some aspects of the protective effect were attenuated after 8 weeks, and the factors responsible for the effect vary among the measures.

Effects of eccentric exercise on microcirculation and microvascular oxygen pressures in rat spinotrapezius muscle

A single bout of eccentric exercise results in muscle damage, but it is not known whether this is correlated with microcirculatory dysfunction. We tested the following hypotheses in the spinotrapezius muscle of rats either 1 (DH-1; n = 6) or 3 (DH-3; n = 6) days after a downhill run to exhaustion (90-120 min; -14 degrees grade): 1) in resting muscle, capillary hemodynamics would be impaired, and 2) at the onset of subsequent acute concentric contractions, the decrease of microvascular O(2) pressure (Pmv(o(2))), which reflects the dynamic balance between O(2) delivery and O(2) utilization, would be accelerated compared with control (Con, n = 6) rats. In contrast to Con muscles, intravital microscopy observations revealed the presence of sarcomere disruptions in DH-1 and DH-3 and increased capillary diameter in DH-3 (Con: 5.2 +/- 0.1; DH-1: 5.1 +/- 0.1; DH-3: 5.6 +/- 0.1 mum; both P < 0.05 vs. DH-3). At rest, there was a significant reduction in the percentage of capillaries that sustained continuous red blood cell (RBC) flux in both DH running groups (Con: 90.0 +/- 2.1; DH-1: 66.4 +/- 5.2; DH-3: 72.9 +/- 4.1%, both P < 0.05 vs. Con). Capillary tube hematocrit was elevated in DH-1 but reduced in DH-3 (Con: 22 +/- 2; DH-1: 28 +/- 1; DH-3: 16 +/- 1%; all P < 0.05). Although capillary RBC flux did not differ between groups (P > 0.05), RBC velocity was lower in DH-1 compared with Con (Con: 324 +/- 43; DH-1: 212 +/- 30; DH-3: 266 +/- 45 mum/s; P < 0.05 DH-1 vs. Con). Baseline Pmv(O(2)) before contractions was not different between groups (P > 0.05), but the time constant of the exponential fall to contracting Pmv(O(2)) values was accelerated in the DH running groups (Con: 14.7 +/- 1.4; DH-1: 8.9 +/- 1.4; DH-3: 8.7 +/- 1.4 s, both P < 0.05 vs. Con). These findings are consistent with the presence of substantial microvascular dysfunction after downhill eccentric running, which slows the exercise hyperemic response at the onset of contractions and reduces the Pmv(O(2)) available to drive blood-muscle O(2) delivery.

The role of exercising muscle length in the protective adaptation to a single bout of eccentric exercise.

The purpose of this study was to determine if the protective adaptation to a single bout of eccentric exercise (repeated bout effect) is dependent on the muscle length at which the eccentric contractions are performed. Ten subjects (six men, four women) performed two bouts of 120 isokinetic eccentric contractions separated by 2 weeks (target intensity was 90% of maximum isometric strength at 70 degrees). In the initial bout one limb exercised from 30 degrees to 70 degrees of knee flexion (short initial bout; SIB) and the contralateral limb exercised from 70 degrees to 110 degrees (long initial bout; LIB). For the repeated bout 2 weeks later, the limb that initially exercised at a short length now exercised at a long length (long repeated bout; LRB) and the limb that initially exercised at a long length now exercised at a short length (short repeated bout; SRB). Isometric strength and pain (scale 0-10) were assessed immediately post exercise and on the next 3 days. Strength loss and pain were greater following LIB versus SIB (strength loss P < 0.01; pain P < 0.001) and following LRB versus SRB (strength loss P < 0.01; pain P < 0.001). Strength loss and pain were not different between LIB and LRB. Pain was significantly greater following SIB compared with SRB (P < 0.05). Strength loss was not different between SIB and SRB. These results confirm that the symptoms of muscle damage are highly dependent on exercising muscle length and also demonstrate that the repeated bout effect is dependent on muscle length. Performing an initial bout of eccentric exercise at a shortened muscle length did not protect against strength loss and pain following a repeated bout at a longer muscle length. Data are given as mean (SE) unless otherwise stated.

Changes in the relationship between joint angle and torque production associated with the repeated bout effect

A single bout of eccentric exercise induces a protective adaptation against damage from a repeated bout. The aim of this study was to determine whether this repeated bout effect is due to a change in the length–tension relationship. Twelve individuals performed an initial bout of six sets of 10 eccentric quadriceps contractions and then performed a repeated bout 2 weeks later. Eccentric contractions were performed on an isokinetic dynamometer at 1.04 rad · s−1 with a target intensity of 90% of isometric strength at 70° of knee flexion. Isometric strength and pain were recorded before and after both eccentric bouts and on each of the next 3 days. Isometric strength was tested at 30°, 50°, 70°, 90° and 110° of knee flexion. On the days following the initial bout, there was a significant loss of isometric strength at all knee flexion angles except 110° (bout×angle: P <0.01). On day 2, strength averaged 86% of baseline for 30–90° and 102% of baseline for 110°. Strength loss and pain after the initial bout was contrasted by minimal changes after the repeated bout (pain: P <0.001; strength: P <0.01). The repeated bout effect was associated with a rightward shift in the length–tension curve; before the repeated bout, isometric strength was 6.8% lower at 30° and 13.6% higher at 110° compared with values before the initial bout (bout×angle: P <0.05). Assuming that torque production at 110° occurs on the descending limb of the length–tension curve, the increase in torque at 110° may be explained by a longitudinal addition of sarcomeres. The addition of sarcomeres would limit sarcomere strain for subsequent eccentric contractions and may explain the repeated bout effect observed here.