Indirect markers of muscle damage and collagen breakdown were recorded for up to 9 days after a bout of concentric, followed by a bout of eccentric, muscle actions. Nine untrained participants performed two bouts of 50 maximum effort repetitions on an isokinetic dynamometer (angular velocity 1.05 rad·s-1, range of motion 1.75 rad). An initial concentric bout of muscle actions was followed by an eccentric bout 21 days later, using the same knee extensors. Concentric actions induced no changes in maximum voluntary isometric contraction force (MVC), nor induced any changes in the serum enzyme activities of creatine kinase, a lactate dehydrogenase isoenzyme (LDH-1), or alkaline phosphatase. Similarly, concentric actions induced no change in markers of collagen breakdown, namely plasma hydroxyproline and serum type 1 collagen concentration. In contrast, eccentric actions induced a 23.5 ± 19.0% (mean ± s) decrease in MVC immediately post-exercise (P < 0.05), and increased the serum enzyme activities of creatine kinase and LDH-1 to 486 ± 792 and 90 ± 11 IU·l-1 respectively on day 3 post-exercise, and to 189 ± 159 and 96 ± 13 IU l-1 respectively on day 7 post-exercise (all P < 0.05). Eccentric actions induced no significant changes in plasma hydroxyproline, but increased collagen concentration on days 1 and 9 post-exercise (48.6% and 44.3% increases above pre-exercise on days 1 and 9 respectively; both P < 0.05). We conclude that eccentric but not concentric actions may result in temporary muscle damage, and that collagen breakdown may also be affected by eccentric actions. With caution, indices of collagen breakdown may be used to identify exercise-induced damage to connective tissue.
"While GTO feedback can be overridden by cognitive processes in the CNS, to allow an athlete to increase performance, it is likely that local peripheral systems can prevent the level of excess muscle contraction that could result in failure or damage. Unaccustomed exercise, particularly eccentric muscle contractions, initiates mechanical muscle damage of varying degrees . Metabolic muscle disturbance is thought to result in release of cellular components through a cascade of events, which begin with depletion of ATP and result in the leakage of extracellular calcium ions into intracellular space, due to both Na-K-ATPase and Ca 2+ -ATPase pump dysfunction. "
[Show abstract][Hide abstract] ABSTRACT: The appearance of creatine kinase (CK) in blood has been generally considered to be an indirect marker of muscle damage, particularly for diagnosis of medical conditions such as myocardial infarction, muscular dystrophy, and cerebral diseases. However, there is controversy in the literature concerning its validity in reflecting muscle damage as a consequence of level and intensity of physical exercise. Nonmodifiable factors, for example, ethnicity, age, and gender, can also affect enzyme tissue activity and subsequent CK serum levels. The extent of effect suggests that acceptable upper limits of normal CK levels may need to be reset to recognise the impact of these factors. There is a need for standardisation of protocols and stronger guidelines which would facilitate greater scientific integrity.
The purpose of this paper is to examine current evidence and opinion relating to the release of CK from skeletal muscle in response to physical activity and examine if elevated concentrations are a health concern.
Journal of nutrition and metabolism 01/2012; 2012(4):960363. DOI:10.1155/2012/960363
"We believed that 10 sets of 8-RM should have provided a high load (intensity) and volume. Brown et al. reported elevated urine (Brown et al., 1997), but not plasma OHP (Brown et al., 1999), after accentuated, eccentric (lengthening) contractions, which is likely a higher stimulus than ours. Further, because bicycles are a means of transportation for most Danes, our subjects could be considered somewhat trained. "
[Show abstract][Hide abstract] ABSTRACT: Exercise increases the synthesis of collagen in the extracellular matrix of skeletal muscle. Breakdown of skeletal muscle collagen has not yet been determined because of technical limitations. The purpose of the present study was to use local sampling to determine skeletal muscle collagen breakdown. Microdialysis fibers were tested in vitro to predict bath hydroxyproline (OHP) concentrations. We used an N-methyl-N-[tert-butyldimethyl-silyl]trifluoroacetimide derivative to analyze OHP using gas chromatography-mass spectroscopy (GC-MS) and compared the results with a colorimetric OHP assay. Ten young, healthy male subjects performed a bout of resistance exercise with one leg, followed 17-21 h later by in vivo skeletal muscle sampling by microdialysis in exercised (EX) and control (CON) legs. Microdialysis reliably predicted [OHP] in vitro (R(2)=0.90). Analysis with GC-MS was strongly correlated to traditional analysis methods (CON: slope=1.03, R(2)=0.896, and P<0.05, EX: slope=0.795, R(2)=0.896, and P<0.05). We conclude that in vitro, microdialysis fibers were able to measure OHP concentrations and were sensitive to changes in concentrations, a strenuous bout of exercise did not increase skeletal muscle collagen breakdown 17-21 h post-exercise, and our measurement of OHP using GC-MS was in agreement with traditional assays.
Scandinavian Journal of Medicine and Science in Sports 12/2011; 21(6):e1-8. DOI:10.1111/j.1600-0838.2010.01105.x · 2.90 Impact Factor
"Different kinds of exercises cause various muscle damages. However, eccentric muscle contractions cause more intensive muscle damage when compared with other kinds of contraction (Brown et al., 1999). The amount of isoenzyme produced by any tissue is determined genetically. "
[Show abstract][Hide abstract] ABSTRACT: The present study assessed the effects of rope training and weighted rope training on muscle damage sustained by basketball players. The study group comprised 36 male basketball players, all of whom have a minimum of 4 years experience of basketball. Participants were aged between 17 and 19 years, and played in the junior league. The Rope Group (n = 12) and Weighted Rope Group (n = 12) received one week preparatory rope training, in addition to technical training. They then trained three days per week for eight weeks. A control group (n = 12) received only technical training for three days per week for eight weeks. In the first and last training sessions, venous blood samples were obtained from subjects before and after the training. The samples were tested for creatine kinase (CK), leukocyte and erythrocyte levels. Statistical analysis of the data was conducted with SPSS (Version 10.0). T-test and ANOVA were used to test for normality level and multi comparison tests, at the 0.05 and 0.01 levels. The results indicated that creatine kinase and leukocyte levels, which are the indicators of muscle damage, increased following high-intensity physical activity ; furthermore, erythrocyte level increased in line with exercise in order to transport oxygen to tissues. The findings suggest that intensive weighted rope training causes damages to muscles.
Data provided are for informational purposes only. Although carefully collected, accuracy cannot be guaranteed. The impact factor represents a rough estimation of the journal's impact factor and does not reflect the actual current impact factor. Publisher conditions are provided by RoMEO. Differing provisions from the publisher's actual policy or licence agreement may be applicable.