Effects of age and arthritis, and cognitive and physical demand, on performance on a continuous tracking task using knee flexions and extensions

The purpose of this study was to establish if older individuals' poorer performance on a motor task using the knee is due to physical (velocity of movement) or cognitive (compatibility of target and subject movement) factors, and to establish if peripheral sensorimotor damage caused by osteoarthritis leads to further deterioration of motor performance. Participants were 24 healthy younger adults, 24 older adults without osteoarthritis, and 22 older adults with osteoarthritis of the knee. Customized software (Advanced Motion Technology, Phoenix, AZ) generated a moving, on-screen sine wave and disc. Participants were instructed to keep the disc on the sine wave by extending and flexing the knee. Compatibility was affected by having leg movements and on screen disc movement be in the same or different directions. Participants completed 10 trials in each of these conditions, which were crossed with both slow and fast movements of the sine wave target across the screen. Overall, younger subjects performed better than older adults and older adults without osteoarthritis performed better than older adults with osteoarthritis. Age-related changes in motor performance were found to be due to both physical and cognitive manipulations and in some comparisons osteoarthritis heightened the effects.