Isotonic dynamometry for the assessment of power and fatigue in the knee extensor muscles of females

Clin Physiol. 2000 May;20(3):225-33. doi: 10.1046/j.1365-2281.2000.00250.x.


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.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adult
  • Biomechanical Phenomena
  • Exercise / physiology*
  • Female
  • Humans
  • Isotonic Contraction
  • Knee Injuries / etiology*
  • Knee Injuries / physiopathology
  • Knee Joint / physiology*
  • Muscle Fatigue / physiology*
  • Muscle, Skeletal / physiology
  • Weight-Bearing