gms | German Medical Science

Motor performance always becomes integrated in the specific aims of human actions. Human performance is finite, and performance abilities are known to decline with age. Krampe et al. (2003, p. 211) postulated “older adults must invest increasing amounts of their cognitive resources into the co-ordination of bodily functions such as balance and gait“. In contrast to the “concept of resources” (e.g., Kahneman, 1973), postural control and supra-postural activity may not compete for central processing resources (e.g., Woollacott; Shumway-Cook 2002). Rather, postural control may be modulated to facilitate the performance of supra-postural tasks (Stoffregen et al., 1999, 2000).

Elderly participants (N= 8; mean age: 58.9 years) took part in a course of co-ordination practice of the Hamburger-Inline-Skating School (HIS). The task setting was similar to that used by Stoffregen et al. (1999, 2000). Subjects were asked to focus on two different targets while balancing on an ankle-exercise board (gyroscope; cf., Wagner et al., 2003). In Inspection trials the goal was to look at the targets (which were blank). In Search trials subject were asked to count certain letters in a text. Targets were either near (small sheets of paper) or far (posters). Each trial took 45 seconds. Sequences of targets and tasks were randomised. The procedure was repeated five times (one baseline: without task; four treatments: supra-postural task Inspection vs. Search).

The subjects were given a 5-second period to get used to the balance disc, then they did either the Inspection, or the Search task for 15 seconds (t1) before the target switches from near to far (paper to poster) or the other way round. Another 10 sec period for rearrangement was given, before the next task started (t2). Balance performance was evaluated in two intervals t1 (5-20 sec) and t2 (30-45 sec). We measured sway by calculating the deviation of the angular rates of the ankle-exercise board (RMSphi, theta, psi [°]).

An ANOVA (2x2) revealed significant main effects of target distance (F(1,14)= 14.66; p<.002) and of task (F(3,42)= 3.17; p<.034). There were no effects of task sequence or of trials (learning). Neither the supra-postural tasks, nor the different targets decreased the balance performance of the elderly adults on the balance board compared with the baseline measuring without any tasks! The Search task was associated with reduced sway, relative to the Inspection task.

Smart balance performance emerged during the current, task-specific demand without apparent strain of central resources. We found the same effect in a study of one-leg-stance on the normal ground with elderly adults by using a motion analysis system (Lippens, Nagel, Schröder, 2006). These results are in accordance with previous studies of supra-postural tasks (e.g., Stoffregen et al., 1999, 2000) and of balance performance of elderly (Stoffregen et al., 2006).