Exercise-induced skeletal muscle damage and adaptation following repeated bouts of eccentric muscle contractions

• Published in: Journal of sports sciences Vol. 15; no. 2; pp. 215 - 222
• Main Authors: Brown, S. J., Child, R. B., Day, S. H., Donnelly, A. E.
• Format: Journal Article
• Language: English
• Published: London Taylor & Francis 01-04-1997; Taylor and Francis
• Subjects: Adaptation, Physiological; Adult; Analysis of Variance; Biological and medical sciences; Creatine; Creatine Kinase - blood; Damage; Eccentric; Exercise; Exercise - physiology; Female; Fundamental and applied biological sciences. Psychology; Humans; Isometric Contraction - physiology; Kinase; Male; Muscle; Muscle Fatigue - physiology; Muscle, Skeletal - physiology; Physical Exertion; Space life sciences; Striated muscle. Tendons; Vertebrates: osteoarticular system, musculoskeletal system; Physical exercise; Human; Enzyme; Creatine kinase; Transferases; Eccentric; Striated muscle; Muscle contraction; Adaptation
• ISSN: 0264-0414; 1466-447X
• DOI: 10.1080/026404197367498

Repeated bouts of eccentric muscle contractions were used to examine indirect indices of exercise-induced muscle damage and adaptation in human skeletal muscle. Twenty-four subjects (18 females, 6 males) aged 20.0-1.4 years (mean - S.D.) performed an initial bout of either 10 (n = 7), 30 (n = 9) or 50 (n = 8) maximum voluntary eccentric contractions of the knee extensors, followed by a second bout of 50 contractions 3 weeks later using the same leg. Muscle soreness was elevated after all bouts (P < 0.05, Wilcoxon test), although the initial bout reduced the soreness associated with the second bout. Force loss and a decline in the 20:100 Hz percutaneous electrical myostimulation force ratio were observed after all exercise bouts (P < 0.01). Serum creatine kinase activity was elevated following the initial bouts of 30 and 50 repetitions (P < 0.01), but there was no increase following 10 repetitions. No increase in serum creatine kinase activity was observed in any group following the second bout of contractions (P > 0.05). We conclude that skeletal muscle adaptation can be brought about by a single bout of relatively few eccentric muscle contractions. Increasing the number of eccentric muscle repetitions did not result in an increased prophylactic effect on skeletal muscle.