Motor control of the knee as a function of age and range of motion.

The purpose of this study was to extend the findings of age-related changes in force fluctuation of musculature of the lower extremity by examining whether accuracy of movement differs between young, middle-aged, and older adults depending on the angular position of the lower leg when completing a continuous tracking task. Participants were 24 healthy young adults (17 to 25 years of age), 24 middle-aged adults (40 to 50 years of age), and 24 older adults (65 to 75 years of age). Performance was assessed during active leg flexion and extension movements within end (10 to 40 degrees flexion) and mid (60 to 90 degrees flexion) ranges of knee motion. Older individuals performed more poorly on the motor task, as indicated by a greater mean absolute deviation from the target (mean [M] = 31.96 mm, standard deviation [SD] = 23.83 mm) compared with the young group (M = 10.59 mm, SD = 10.51 mm) and middle-aged group (M = 9.09 mm, SD = 4.55 mm). There was no interaction between age and range of motion. Although clear age-related differences in performance were obtained, there was no evidence that age-related differences in dynamic position sense affected voluntary motor control performance as measured in this study. Whatever factors contribute to age-related changes in motor performance control appear to have consistent affect on performance throughout the range of motion of the knee.