Variability as a characteristic of immature motor systems: an electromyographic study of swimming in the newborn rat.

Swimming behaviour was studied in neonate rats by carrying out electromyographic recordings. The study showed that the early swimming pattern was characterized by highly instable temporal parameters. A decrease was found to occur with age in the variability of the instantaneous period in each leg and in that of the antiphase pattern. Moreover, a dissociation occurred during development between the foreleg and the backleg activity. While patterns involving the forelegs always remained extremely instable, a considerable improvement was found to occur with time in the hindlimb activity.