Altered Bimanual Kinetic and Kinematic Motor Control Capabilities in Older Women

Abstract

Older women may experience critical neuromuscular impairments interfering with controlling successful bimanual motor actions. Our study aimed to investigate altered bimanual motor performances in older women compared with younger women by focusing on kinetic and kinematic motor properties. Twenty-two older women and 22 younger women performed bimanual kinetic and kinematic motor tasks. To estimate bimanual kinetic functions, we calculated bimanual maximal voluntary contractions (i.e., MVC) and force control capabilities (i.e., mean force, accuracy, variability, and regularity of the total force produced by two hands) during bimanual hand-grip submaximal force control tasks. For bimanual kinematic performances, we assessed the scores of the Purdue Pegboard Test (i.e., PPT) in both hands and assembly tasks, respectively. For the bimanual MVC and PPT, we conducted an independent t-test between two groups. The bimanual force control capabilities were analyzed using two-way mixed ANOVAs (Group × Force Level; 2 × 2). Our findings revealed that the older women showed less bimanual MVC (p = 0.046) and submaximal force outputs (p = 0.036) and greater changes in bimanual force control capabilities as indicated by a greater force variability (p = 0.017) and regularity (p = 0.014). Further, the older women revealed lower scores of PPT in both the hands condition (p < 0.001) and assembly task condition (p < 0.001). The additional correlation analyses for the older women showed that lower levels of skeletal muscle mass were related to less bimanual MVC (r = 0.591; p = 0.004). Furthermore, a higher age was related to lower scores in the bimanual PPT assembly task (r = -0.427; p = 0.048). These findings suggested that older women experience greater changes in bimanual motor functions compared with younger women.

Keywords: aging; bimanual force control; hand-grip force; motor dexterity.

Figure 1

Experimental setup. (a) Isometric hand-grip force measurement systems to estimate bimanual MVC and submaximal force control capabilities. (b) Three types of visual feedback on the LED monitor. (c) Purdue Pegboard Test (PPT).

Figure 2

Bimanual maximal and submaximal isometric forces (M ± SE). (a) Maximal force showing a significant group main effect. (b) Submaximal mean force showing a significant Group × Force Level interaction. Asterisk (*) indicates a significant difference between two groups. Number sign (#) denotes a significant difference between 10% and 40% of MVC.

Figure 3

Bimanual force control performances (M ± SE). (a) Force accuracy showing a significant Force Level main effect. (b) Force variability showing a significant Group × Force Level interaction. (c) Force regularity showing significant Group and Force Level main effects. Asterisk (*) indicates a significant difference between two groups. Number sign (#) denotes a significant difference between 10% and 40% of MVC.

Figure 4

Purdue Pegboard Test scores in both hands and assembly tasks (M ± SE). (a) PPT scores in both hands task showing a significant difference between groups. (b) PPT scores in bimanual assembly task showing a significant difference between groups. Asterisk (*) indicates a significant difference between two groups.

Figure 5

Correlation findings between skeletal muscle mass versus bimanual MVC and age versus PPT scores in bimanual assembly task for the older women group. (a) Lower levels of skeletal muscle mass were significantly related to less bimanual maximal forces. (b) Higher age was significantly related to lower bimanual PPT assembly scores.