Isotonic dynamometry for the assessment of power and fatigue in the knee extensor muscles of females.
Impairments in muscle power production and recovery following short-duration intense activity could lead to decreased performance and risk of injury. We developed a power test for the knee extensor muscles using torque-velocity testing and moderate isotonic loads. Twenty-eight female volunteers performed three maximal efforts at each of four isotonic loads (27.1, 40.6, 54.2 and 67.8 N. m). If the calculated regression line for the torque-velocity data had an r2 >/= 0.95 (i.e. an acceptable test), maximal power (408 +/- 56 W) was computed from the data. Immediately after torque-velocity testing, the subjects repeated maximal effort knee extensions with 33.9 N. m for three bouts of 15 repetitions with 15 s of rest to produce muscle fatigue, defined as a decrease in power output during isotonic exercise. After a 4 min rest, the torque-velocity test was repeated and power calculated (345 +/- 48 W). For the group, the recovery of maximal power after the fatigue protocol was 85%. The extremes were represented by one subject who recovered only 70% of her maximal power and another who recovered completely (>98%). Physiological differences in muscle power following repeated exercise could have an impact on the outcome of therapeutic interventions for sports injuries, fatigue syndromes and occupational over-use conditions.
Stauber
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Department of Physiology, West Virginia University, PO Box 9229, Morgantown, WV 26506-9229, USA.
Barill
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ER
Stauber
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RE
Miller
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GR
D000328:Adult; D001696:Biomechanical Phenomena; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D007551:Isotonic Contraction; D007718:Knee Injuries / Q000209:etiology* / Q000503:physiopathology; D007719:Knee Joint / Q000502:physiology*; D018763:Muscle Fatigue / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology; D016474:Weight-Bearing