F-57 Free Communication/Slide - Neural Control of Movement and Balance: MAY 29, 2009 3:15 PM - 5:00 PM: ROOM: 201
Previous studies showed an age-related increase in perception of sense of effort (SOE) during single-joint upper-extremity force/torque production tasks. In the current study, we further examined the interaction effects of multiple joint positions and age on SOE perceptions.
PURPOSE: To examine the effects of age and joint position on effort perception during multi-joint upper-extremity force/torque production tasks.
METHODS: Fifteen healthy, younger individuals (8 males, 7 females) between 20-40 years of age and 15 healthy, older individuals (8 males, 7 females) between 65-75 years of age participated in this study. All participants performed isometric elbow joint flexion and extension tasks in the horizontal plane using their dominant arm at three different elbow joint angles (45°, 90°, and 135°). At each joint position, the participants were instructed first to perform maximum voluntary contractions (MVC), and were thereafter asked to produce joint torques that corresponded to effort levels of 1, 3, 5, 7, and 9 on a modified Borg CR-10 scale. The 30 conditions (five effort levels × three joint angles × two tasks) were tested in a random order. Elbow joint torque (EJT) was measured using a Biodex System 3 Pro dynamometer. A between-within subjects factorial ANOVA design was used to assess the effects of age, task (flexion or extension), joint position, and effort level on EJT (absolute and relative [normalized to MVC strength]).
RESULTS: There was no significant interaction effect of joint position and age on SOE for both absolute (F2,84 = 0.58, P = 0.56) and relative (F2,84 = 0.26, P = 0.78) EJT. There was significant effects of joint position on SOE in both age groups (F2,84 = 4.29, P = 0.017 and F2,84 = 5.56, P = 0.006 respectively for absolute and relative EJT). There was significant difference between EJT at 45° and 90° (P = 0.033), 45° and 135° (P = 0.008), but there was no significant difference between 90° and 135° (P > 0.05) joint angles for both absolute and relative EJT.
CONCLUSIONS: Whereas our previous study suggested age-related increase in SOE perceptions during single joint EJT production tasks, the present study suggests that age-related effects were independent of joint positions. Further, in all age groups, motor tasks are perceived as more effortful as joint angle increases beyond 45° joint position.