Abstract
The EMG pattern in the elbow flexors during the performance of relatively slow (non-ballistic) targeted flexor and extensor movements with different velocities and amplitudes and subsequent fixation of a reached position was studied in healthy humans. Using a servocontrolled mechanostimulator, steady external loading was applied to the arm, which provided performance of the movements and their termination exclusively by the flexor activity, leaving the extensors passive. In all cases, even at very slow movements, EMG activity of the flexors at transition of the joint from one equilibrium state to another was shown to contain a clear dynamic phase followed by a phase of stationary activity. The level of the latter, generated during fixation of a reached position, was practically independent of the amplitude of a movement within the 0–60° range of the joint angles. Thus, the force developed by the flexors at the dynamic EMG phase became fixed when a new equilibrium joint position was reached and did not decrease in the course of a considerable drop in the efferent activity level, when the stationary phase of this activity began. The dynamic EMG phase included two components. The first component was related to leaving the equilibrium state with a certain acceleration, while the second component was probably involved in the velocity control and stoppage of the joint in a new equilibrium position. We suppose that retention of the joint in the equilibrium state is not provided exclusively by formation of a certain equilibrium level of efferent activity (as it is postulated by the equilibrium point hypotheses); it results from some coordinated modifications of the dynamic muscle activity that provide achievement of equilibrium in a certain position within a certain stage of the movement.
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References
A. G. Fel’dman,Central and Reflex Mechanisms of Movement Control [in Russian], Nauka, Moskow (1979).
E. Bizzi, A. Polit, and P. Morasso, “Mechanisms underlying achievement of final head position,”J. Neurophysiol.,39, 435–444 (1976).
E. Bizzi, N. Accornero, W. Chapple, and N. Hogan, “Arm trajectory formation in monkeys,”Exp. Brain Res.,46, 139–143 (1982).
E. Bizzi, F. Mussa-Ivaldi, and S. Gistzer, “Does the nervous system use equilibrium-point control to guide single and multiple joint movements?,”Behav. Brain Sci.,15, 603–613 (1992).
Z. Hasan and R. M. Enoka, “Isometric torque-angle relationship and movement-related activity of human elbow flexors: implications for the equilibrium-point hypothesis,”Exp. Brain Res.,59, 441–450 (1985).
B. C. Abbot and X. M. Aubert, “The force exerted by active striated muscle during and after change of length,”J. Physiol. 117, 77–86 (1952).
P. M. H. Rack and D. R. Westbury, “The short range stiffness of active mammalian muscle and its effect on mechanical properties,”J. Physiol.,240, 331–350 (1974).
A. I. Kostyukov, “Muscle dynamics: dependence of muscle length on changes in external load,”Biol. Cibern.,56, 375–387 (1987).
A. I. Kostyukov and A. N. Tal’nov, “Effects of torque disturbances on elbow joint movements evoked in unanesthetized cats by microstimulation of the motor cortex,”Exp. Brain Res.,84, 374–382 (1991).
A. N. Tal’nov and A. I. Kostyukov, “Hysteresis after effects in single-joint voluntary movements in humans,”Neirofiziologiya/Neurophysiology,26, No. 2, 83–90 (1994).
M. Hallet and C. D. Marsden, “Ballistic flexion movements of the human thumb,”J. Physiol.,294, 33–50 (1979).
S. A. Wallace, “An impulse-timing theory for reciprocal control of muscular activity in rapid, discrete movements,”J. Mot. Behav.,13, 144–160 (1981).
R. Benecke, H. M. Meinck, and B. Conrad, “Rapid goal-directed elbow flexion movements: limitations of speed control system due to neural constraints,”Exp. Brain Res.,59, 470–477 (1985).
D. M. Corcos, G. C. Agarwal, B. P. Flaherry, and G. L. Gottlieb, “Organizing principles for single-joint movements. 4. Implications for isometric contractions,”J. Neurophysiol.,64, 1033–1042 (1990).
G. L. Gottlieb, D. M. Corcos, and G. C. Agarwal, “Organizing principles for single-joint movements. I. A speed-insensitive strategy,”J. Neurophysiol.,62, 342–357 (1989).
G. L. Gottlieb, D. M. Corcos, G. C. Agarwal, and M. L. Latash, “Organizing principles for single-joint movements. 3. Speed-insensitive strategy as a default,”J. Neurophysiol.,63, 625–636 (1990).
G. L. Gottlieb, M. L. Latash, D. M. Corcos, et al., “Organizing principles for single-joint movements. 5. Agonist-antagonist interactions,”J. Neurophysiol.,67, 1417–1427 (1992).
D. M. Corcos, G. L. Gottlieb, and G. C. Agarwal, “Organizing principles for single-joint movements. 2. A speed-sensitive strategy,”J. Neurophysiol.,62, 358–368 (1989).
A. Polit and E. Bizzi, “Characteristics of motor programs underlying arm movements in monkeys,”J. Neurophysiol.,42, 183–194 (1979).
A. N. Tal’nov, V. L. Cherkassky, and A. I. Kostyukov, “Movement-related and steady-state electromyographic activity of human elbow flexors in slow transition movements between two equilibrium states,”Neuroscience,79, 923–933 (1997).
D. J. Cooke and S. H. Brown, “Movement-related phasic muscle activation. 2. Generation and functional role of the triphasic pattern,”J. Neurophysiol.,63, 465–475 (1990).
S. B. Adamovich, M. B. Berkinblit, A. G. Fel’dman, “Principles of the motor control in humans,”Itogi Nauki Tekh. Ser. Fiziol. Cheloveka i Zhivotnykh,43 (1990).
A. I. Kostyukov and O. E. Korchak, “Length changes of soleus muscle under frequency-modulated distributed stimulation of efferents in isotony,”Neuroscience,82, 943–955 (1998).
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Tal’nov, A.N., Serenko, S.G., Cherkasskii, V.L. et al. Coordination of the dynamic phases of EMG activity in human elbow flexors in the performance of targeted tracking movements. Neurophysiology 30, 168–178 (1998). https://doi.org/10.1007/BF02463430
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DOI: https://doi.org/10.1007/BF02463430