title: The effect of exercise-induced muscle damage on isometric and dynamic knee extensor strength and vertical jump performance.
abstract: In this study, we assessed the effect of exercise-induced muscle damage on knee extensor muscle strength during isometric, concentric and eccentric actions at 1.57 rad x s(-1) and vertical jump performance under conditions of squat jump, countermovement jump and drop jump. The eight participants (5 males, 3 females) were aged 29.5+/-7.1 years (mean +/- s). These variables, together with plasma creatine kinase (CK), were measured before, 1 h after and 1, 2, 3, 4 and 7 days after a bout of muscle damaging exercise: 100 barbell squats (10 sets x 10 repetitions at 70% body mass load). Strength was reduced for 4 days (P< 0.05) but no significant differences (P> 0.05) were apparent in the magnitude or rate of recovery of strength between isometric, concentric and eccentric muscle actions. The overall decline in vertical jump performance was dependent on jump method: squat jump performance was affected to a greater extent than countermovement (91.6+/-1.1% vs 95.2+/-1.3% of pre-exercise values, P< 0.05) and drop jump (95.2+/-1.4%, P< 0.05) performance. Creatine kinase was elevated (P < 0.05) above baseline 1 h after exercise, peaked on day 1 and remained significantly elevated on days 2 and 3. Strength loss after exercise-induced muscle damage was independent of the muscle action being performed. However, the impairment of muscle function was attenuated when the stretch-shortening cycle was used in vertical jumping performance.
authors.affiliation: Military Physiology Laboratory, Defence Medical Research Institute, Defence Science and Technology Agency, Republic of Singapore. christopher_byrne@dsta.gov.sg
authors.forename: Christopher
authors.initials: C
authors.lastname: Byrne
authors.forename: Roger
authors.initials: R
authors.lastname: Eston
mesh_terms: D000328:Adult; D003402:Creatine Kinase / Q000378:metabolism; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D007718:Knee Injuries / Q000503:physiopathology*; D007719:Knee Joint / Q000502:physiology; D008297:Male; D009068:Movement / Q000502:physiology*; D018482:Muscle, Skeletal / Q000293:injuries* / Q000503:physiopathology*; D020127:Recovery of Function / Q000502:physiology; D013647:Task Performance and Analysis
chemical_list: D003402:Creatine Kinase