Multilimb coordination patterns in simultaneous, dissimilar upper and lower limb tasks

Multilimb coordination was examined when subjects clapped (in-phase pattern) while walking (out-of-phase pattern) or galloping (off-phase pattern). Based on previous studies of rhythmic limb movements it was predicted that in-phase frequency-locked coordination would be the most attractive mode, although a previous study by Muzii et al. (1984) had suggested that other coordination modes existed. Subjects clapped and walked or galloped at a preferred speed and at one of four different task manipulations: extended practice, overall speed, temporal and spatial. The resultant multilimb coordination patterns were classified in terms of frequency-locking, phase relationships and stability of between-girdle and within-girdle relationships. Absolute step frequency-locking was the most attractive coordination mode for the clap/walk task, but an unlocked-stable coordination mode was also present. For the clap/gallop, absolute stride frequency-locking was the only attractive coordination mode. Subjects tended to be stable in their preferences across trials and across changes in speed or they adopted a frequency-locked mode. Temporal and spatial manipulations of one limb girdle with respect to the other most commonly resulted in an unlocking of frequency, although there was much inter-subject variability and signs of individual attentional strategies. In general, the results indicated that coordination was a product of a complex interaction of organismic and task constraints, but with many characteristics that are consistent with a general dynamical systems perspective on rhythmic interlimb coordinatio