title: Damage to the human quadriceps muscle from eccentric exercise and the training effect.
abstract: Nine participants performed two bouts of a step exercise, during which the quadriceps muscle of one leg acted eccentrically. Before and after the exercise, isokinetic torque was measured over a range of knee angles to determine the optimum angle for torque. Immediately after the first bout of exercise, the quadriceps showed a significant (P < 0.05) shift of 15.6 +/- 1.4 degrees (mean +/-sx) of its optimum angle in the direction of longer lengths, suggesting the presence of damage. A drop in peak torque, together with delayed soreness and swelling, confirmed that damage to muscle fibres had occurred. After the second bout of exercise, 8 days later, the shift in optimum angle was 10.4 +/- 1.0 degrees, which was significantly less than after the first bout (P < 0.05). Other indicators of damage were also reduced. In addition, the muscle exhibited a sustained shift in optimum angle (3.4 +/- 0.9 degrees), suggesting that some adaptation had taken place after the first bout of exercise. We conclude that muscles like the quadriceps can show evidence of damage after a specific programme of eccentric exercise, followed by an adaptation response. This is despite the fact that the quadriceps routinely undergoes eccentric contractions in everyday activities.
authors.affiliation: Department of Physiology, Monash University, Melbourne, VIC 3800, Australia.
authors.forename: E J
authors.initials: EJ
authors.lastname: Bowers
authors.forename: D L
authors.initials: DL
authors.lastname: Morgan
authors.forename: U
authors.initials: U
authors.lastname: Proske
mesh_terms: D000328:Adult; D001265:Athletic Injuries / Q000150:complications / Q000503:physiopathology*; D004487:Edema / Q000209:etiology; D015444:Exercise; D005260:Female; D006801:Humans; D007869:Leg Injuries / Q000150:complications / Q000503:physiopathology*; D008297:Male; D018482:Muscle, Skeletal / Q000293:injuries* / Q000503:physiopathology*; D010146:Pain / Q000209:etiology; D010806:Physical Education and Training / Q000379:methods*; D019415:Torque