LIMIT-CYCLE PROPERTIES OF RHYTHMIC FOREARM MOVEMENTS

The kinematics of 1- and 2-armed rhythmic forearm movements were exami ned using the methodology and limit cycle modeling strategy of B. A. K ay, J. A. S. Kelso, E. L. Saltzman, and G. Schoner (1987). As frequenc y was paced from 1 to 6 Hz (in steps of 1 Hz), amplitude decreased in all 7 participants, whereas peak velocity showed different trends for different participants. The data of 2 of the 7 participants could be d escribed with Kay et al.'s model. To account for the data of the remai ning 5 participants, a new model was proposed with a dissipative struc ture involving a frequency-dependent Rayleigh term and a standard Van der Pol term. For 2 of these 5 participants, the coefficient of the Va n der Pol term was not significantly different from zero. Contrary to Kay et al.'s model, the new model suggests that the energy bookkeeping of rhythmic forearm oscillations is affected by the frequency of move ment.