Aging Impairs Unimanual and Bimanual Hand-Grip Force Control Capabilities

This study examined age-related changes in unimanual and bimanual hand-grip force control capabilities by focusing on absolute and relative outcome measures. Thirty-two older adults and thirty-two younger adults performed isometric hand-grip force control tasks across three hand conditions (unimanual dominant, unimanual non-dominant, and bimanual) and two submaximal targeted levels (10% and 40% of maximal voluntary contraction). Force control performances were evaluated by calculating absolute and relative variables on force accuracy and variability. Furthermore, to determine which force control variables and experimental conditions effectively indicate age-related sensorimotor control deficits, we conducted receiver operating characteristic curve analyses. Older adults demonstrated impaired force control capabilities at 10% of maximal voluntary contraction collapse across the three hand conditions compared with younger adults, and these deficits were identified by both relative force accuracy and relative force variability. Moreover, relative force accuracy showed a good diagnostic quality at 10% of maximal voluntary contraction. These findings suggested that aging may induce unimanual and bimanual hand-grip force control deficits at a lower targeted level, and these motor impairments were sensitively estimated by quantifying relative force control outcome measures that may reflect age-related muscle weakness as compared with absolute measurements.