Rl. Gajdosik et al., ACCURACY AND VARIABILITY OF LEG VELOCITIES DURING CONCENTRIC AND ECCENTRIC ACTIONS OF THE QUADRICEPS FEMORIS MUSCLES, Perceptual and motor skills, 84(2), 1997, pp. 575-586
This study examined the ability to control leg velocities during conce
ntric and eccentric actions of the right quadriceps muscles. Ten healt
hy women (M age = 25.9 +/- 3.5 yr.) were tested using the Isotonic Pro
gram of the KIN-COM II 500H dynamometer. They attempted to match veloc
ity tracings of 10 degrees, 20 degrees, and 40 degrees/sec. through 70
degrees of knee range of motion at a load equal to 10% of their maxim
al mean concentric force. The actual mean velocities, mean percent dev
iation from the target velocities, and the coefficient of variation fo
r both actions were calculated for 15 degrees-75 degrees (full range o
f motion), 15 degrees-45 degrees (shorter range of motion), and 46 deg
rees-75 degrees (longer range of motion). Separate one-way analyses of
variance with two trial factors (action x velocity) showed faster con
centric velocities through the full and longer ranges of mot ion, and
faster eccentric velocities through the shorter range of motion. Mean
per cent deviations indicated that the eccentric velocities were gener
ally more accurate within all ranges of motion. Larger concentric coef
ficients of variation were found within the full and longer ranges of
motion, and the coefficients of variation for both actions decreased a
s the velocities increased. An exaggerated 'velocity overshoot' at the
onset of both actions probably contributed to differences in the velo
cities and coefficients of variation. The results indicated difference
s between the concentric and eccentric actions, explained in part by t
he testing methodology used and by the known mechanical and physiologi
cal characteristics of the two muscle actions.