PED 1323 Motor Control & Motor Learning

3 reduction in the antagonist coactivation allows

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3. Reduction in the antagonist coactivation allows prime mover torque to not be counteracted by antagonsts. (remember: Coactivation of agonist and antagonists will work against each other and reduce the net torque (force) output from a agonist prime mover,) BUT: a. Reduced coactivation is observed in the elderly 3, 12 b. Reduced coactivation was observed in an isometric contraction in young subjects in which there was no increased EMG of the prime movers 14 c. Some studies find no decrease in antagonist activation with resistance training 15 4. Multijoint/multimuscle coordination for posture and stabilization 4 . e.g., hip, knee, angle, trunk, contralateral leg, & arm muscle activation coordination for leg extension during kick 5. Increased recruitment of more motor units that were previously inactive in a maximal effort not likely, since limb muscle are likely fully recruited at 85% MVC force level 4, 9, 16 6. Increased synchronization of motor units firing , found in some studies, but not all 4 . But synchronization, when it occurs, has not been demonstrated to increase muscle force 4,5 Motor unit firing at a low frequency, producing low force Motor unit firing at a moderate frequency, producing moderate force Motor unit firing at a high frequency, producing high force Motor unit not firing, producing no force Legend Higher force level being produced
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Motor Control Section 2: Muscles fibers types and their use Unit 6a: Neuromuscular adaptations with resistance training Yao et al., J Neurophysiol. 83:441-52, 2000. 7. Enlargement of neuromuscular junction [“functional significance unknown”] 7 8. Reduction in GTO inhibition of muscle activation . Does not occur 8 “Neural adaptations to resistance training” for a healthy young male % of improvement is due to which factor 100 % 0 % From: Physiology of Exercise and Sport, Wilmore & Costill, 1999 The understanding of the exact nature of neural adaptations to resistance training is still in it’s early stages 9 (2005), 13 (2005) 1- Aagaard P. Training-induced changes in neural function. Exerc Sport Sci Rev. 2003, Apr;31(2):61-7 2- Aagaard P, et al. Increased rate of force development and neural drive of human skeletal muscle following resistance training. J Appl Physiol. 2002 Oct;93(4):1318-263 3- Hakkinen K et al., Changes in agonist-antagonist EMG, muscle CSA, and force during strength training in middle-aged and older people J Appl Physiol. 1998 Apr;84(4):1341-9 4- Duchateau et al. Training adaptations in the behavior of human motor units. J Appl Physiol. 2006 Dec;101(6):1766-75. 5- Holtermann et al., Changes in agonist EMG activation level during MVC cannot explain early strength improvement. Eur J Appl Physiol. 2005:94, 593-601 6- Gabriel DA, Kamen G, Frost G. Neural adaptations to resistive exercise: mechanisms and recommendations for training practices. Sports Med. 2006;36(2):133-49.
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