ABSTRACT
The effects of aging on adaptive force control of precision grip while manipulating a small object were compared between older (84.2±8.9 yrs, n=33) and young adults (19.1±0.24 yrs, n=18) from the following perspectives: (1) adaptation to an unfamiliar object with uncertain physical properties during 16 consecutive lifts ; (2) adaptation to an object with a non-slippery (sandpaper) surface during 12 consecutive lifts, followed by 12 consecutive lifts with a slippery (silk) surface ; and (3) adaptation to objects with different weights (0.49, 0.98, 1.96 and 2.94 N) during 24 lifts (6 consecutive lifts for each weight) .During each trial, grip and load forces were monitored. Safety margin force and slip force were evaluated from the data obtained.<BR>The majority of older adults employed a considerably greater safety margin for an unfamiliar object in the initial trials than did young adults, while the minority of the older adults were able to adapt their safety margin force with a few trials, like the young adults. The older adults who overestimated the safety margin force, however, successfully adjusted their grip force to more optimal levels with repeated lifts, suggesting that the adaptive capability of grip force remained even at 90 years of age. The adaptation of older adults, however, was found to be slower (i. e., required more trials) than that of young adults. Upon encountering surface friction change, the safety margin forces in older adults were more strongly affected by the previous surface condition than those in the young adults. In addition, adaptation to a non-slippery surface seemed more difficult than that to a slippery surface with aging. Upon encountering weight change, older adults showed more difficulties in scaling their safety margin forces according to object weights.<BR>Slower adaptation and difficulty in adaptation to the friction or weight change in older adults may reflect the agerelated decline of tactile sensitivity which impaired the signaling of frictional conditions and various discrete events in the hand. In addition, the lift repetition for force adaptation may possibly reflect the age-related deficit or slowing of central processing capacities related to grip force production.
ABSTRACT
A motor performance test was administered to elderly adults in Koganei City and Nangai Village of Japan as the baseline study of Tokyo Metropolitan Institute of Gerontology, Longitudinal Interdisciplinary Study on Aging (TMIG-LISA) . The participants in this study totaled 405 (183 males and 222 females) aged 65 to 84 from Koganei City, and 734 (295 males and 439 females) aged 65 and over from Nangai Village. The test consisted of measurement of grip strength, one-leg stand-ing, walking at preferred and maximum speeds, and finger-tapping. All motor performances examined were higher among males than females, and they all deteriorated with aging. A regional difference was found in terms of motion speed abilities: finger-tapping rate and walking speed were higher among urban residents than rural residents. Individual differences (coefficient of variation) in the motor ability increased with aging, and reached 106% (maximum tapping rate in female) to 290% (maximum walking speed in female) of those in the twenties. Significant correlations between motor abilities were detected indicating that the specificity of the motor ability found in the young may not account for older adults.
ABSTRACT
A study was conducted to determine the effect of aging on motor ability and to establish a test battery for physical fitness in the elderly. The subjects were 150 men aged 18 to 83 years. The test items examined were selected, according to Fleishman's list of motor abilities; (1) trunk flexion, (2) grip and isometric knee extension strength, (3) postural sway with eyes open and closed, (4) step test, (5) walking test at preferred and maximum speeds, (6) simple visual reaction time, (7) peg-board test, (8) finger tapping test at maximum rate and in time to metronome sounds. Performances for the test items, except for preferred walking speed and coefficient of variation in finger tapping at 5 Hz, showed significant decreases with aging. The decrease in motor performance at age 80 years relative to the level at age 20 years was less than 30% for finger dexterity and reaction time, 40-60% for muscle strength, maximum walking speed and the step test, and over 70% for trunk flexion and postural sway with eyes closed. A test battery composed of trunk flexion, grip strength, knee extension, step test, walking as fast as possible, postural sway with eyes closed, and finger tapping, is therefore recommended for assessing the effect of aging on physical fitness.