Indirect evidence of human skeletal muscle damage and collagen breakdown after eccentric muscle actions
ABSTRACT This metadata relates to an electronic version of an article published in Journal of sports sciences, 1999, vol. 17, no. 5, pp. 397-402. Journal of sports sciences is available online at informaworldTM at http://www.informaworld.com/smpp/content~db=all~content=a713776150?words=indirect|evidence&hash=2313990694 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.
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ABSTRACT: Rugby league is a team sport in which players engage in repeated high-intensity exercise involving frequent collisions. Recent research, much of which has involved global positioning system (GPS) technology, has provided coaches and sport scientists with a deeper understanding of match demands, particularly at the elite level. This has allowed for the development of training programmes that prepare players for the most intense contact and running demands likely to be experienced in competition. At the elite level, rugby league players have well-developed aerobic and anaerobic endurance, muscular strength and power, reactive agility, and speed. Upper- and lower-body strength and aerobic power are associated with a broad range of technical and sport-specific skills, in addition to a lower risk of injury. Significant muscle damage (as estimated from creatine kinase concentrations) and fatigue occurs as a result of match-play; while muscle function and perceptual fatigue generally return to baseline 48 h following competition, increases in plasma concentrations of creatine kinase can last for up to 5 days post-match. Well-developed physical qualities may minimise post-match fatigue and facilitate recovery. Ultimately, the literature highlights that players require a broad range of physical and technical skills developed through specific training. This review evaluates the demands of the modern game, drawing on research that has used GPS technology. These findings highlight that preparing players based on the average demands of competition is likely to leave them underprepared for the most demanding passages of play. As such, coaches should incorporate drills that replicate the most intense repeated high-intensity demands of competition in order to prepare players for the worst-case scenarios expected during match-play.Sports medicine (Auckland, N.Z.). 04/2014;
- Journal of Human Kinetics - J HUM KINET. 01/2010; 23:55-61.
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ABSTRACT: This research was designed to measure the levels 01hydroxyproline (HP) in urine alter the application of two diflerent methods of strength training. Thirty fit, healthy men were randomly divided into two groups: exercise (EG) and control (CG). 80th groups provided urine samples priorto training, although only the EG performed 1 repetition maximum (RM); 5RM and 30RM tests. Alter this, the EG performed three series of 5RM. Alter two hours, urine samples were collected lrom the EG. Sixteen days later, the same pl;.ocedure took place using a 30RM protocol. The HP levels in urine were quantified colorimetrically using a spectrophotometer. Statistically signilicant diflerences in HP values were found only lor the the 5RM training method (e.= -22%, P< 0.05). It was concluded that damage to the conjunctive tissue only too k place with 5RM training, thus confirming that one way 01 avoiding stagnation in the adaptation 01 subjects with certain experience 01 strength training is to use more intense methods. However, in such training protocols, the recovery time between sessions should be greater due to the resulting increase in tissue damage.International Journal of Fitness. 01/2010; 6(1):17-23.