Organizing Principles for voluntary movement: Extending single joint rules.
Almeida, Gil L., Di-an Hong, Daniel Corcos and Gerald L. Gottlieb.
School of Kinesiology (M/C 194), University of Illinois at Chicago,
Chicago, Illinois 60680, Universidade Estadual de Campinas, Campinas,
S[diaeresis]io Paulo, Brazil 13100, Department of Molecular Biophysics and
Physiology, Rush Medical College, Chicago, Illinois 60612, Department of
Neurological Sciences, Rush Medical College, Chicago, Illinois 60612, Boston
University - NeuroMuscular Research Center, 44 Cummington St., Boston,
Massachussetts 02215, (617) 353-8984, fax (617) 353-5737, email:
GLG@bu.edu.
APStracts 2:0161N, 1995.
SUMMARY AND CONCLUSIONS
1. Four subjects performed fast flexions of the elbow or shoulder over three
different distances. Elbow flexions were done both in a horizontal, single
degree of freedom manipulandum and in a sagittal plane with the unconstrained
limb. Shoulder flexions were only performed in the sagittal plane by the
unconstrained limb. We simultaneously recorded kinematic and EMG patterns at
the focal joint, that which the subject intentionally flexed, and at the
other, non-focal joint that the subject had been instructed to not flex. 2.
Comparisons of the elbow EMG patterns across tasks show that agonist and
antagonist muscles were similar in pattern but not size, reflecting the net
muscle torque patterns. Comparisons at the shoulder, also revealed similar EMG
patterns across tasks that reflected net muscle torques. 3. Comparisons of EMG
patterns across joints show that elbow and shoulder flexors behaved similarly.
This was not true of the extensors. The triceps EMG burst was delayed for
longer distances but the posterior deltoid had an early, distance invariant
onset. 4. Similarities in EMG reflect torque demands, required at the focal
joint to produce flexion and at the non-focal joint to reduce extension
induced by dynamical interactions with the focal, flexing joint. These
similarities appear in spite of very different kinematic intentions and
outcomes. This argues against a strong role for length sensitive reflexes in
their generation. 5. These results support the hypothesis that movements are
controlled by muscle activation patterns that are planned for the expected
torque requirements of the task. This general rule is true whether we are
performing single joint or multiple joint movements, with or without external
constraints. The similarities between single and multijoint movement control
may be a consequence of ontogenetic development of multijoint movement
strategies that prove useful and are therefore also expressed under the
constrained conditions of specialized tasks such as those performed in single-
joint manipulanda.
Received 11 January 1995; accepted in final form 22 May 1995.
APS Manuscript Number J25-5.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 30 May 1995.