PED 1323 Motor Control & Motor Learning

Alwyn is also recognized and certified by the

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Alwyn is also recognized and certified by the National Academy of Sports Medicine, the American College of Sports Medicine, the British Association of Sports And Exercise Sciences, Kingsports International Australia, the Society for Weight Training Injury Specialists, USA Weightlifting and the Chek Insitute of Corrective High Performance Exercise Kinesiology. Visit Alwyns site at... ***********************************************
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Motor Control Section 3: Motor control aspects of resistance training Unit 7: Additional exercise science applications of spinal reflexes The SSC and fatigue If you maximally jump up & down 20X, why do you progressively jump lower? What is the physiological basis of the muscle fatigue? Review: The combined contribution of decending voluntary drive and reflex activation of motoneurons Exhaustive SSC fatigue (e.g., 100 jumps) can dramatically reduce the reflex contribution to force production through deterioration in the sensitivity of the reflex after fatigue because of decreased pH: direct inhibition of muscle spindle firing activating other chemical sensitive afferent nerve endings, to act through inhibitory interneuron, to inhibit homonymous motoneuron INHIBITORY (-) = DECREASE THE PROBABILITY THAT THE POSTSYNAPTIC CELL WILL FIRE AN ACTION POTENTIAL hyperpolarize the cell away from threshold for firing an AP + + + - + - + + threshold Muscle fiber contractile activity inhibition What is the physiological basis of a reduction in force production with repeated SSC movements (e.g., jumping, hitting etc.)? Where are GOLGI TENDON ORGANS? What do GOLGI TENDON ORGANS detect? Type Ib afferent carries information from tendon organ
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Motor Control Section 3: Motor control aspects of resistance training Unit 7: Additional exercise science applications of spinal reflexes What happens when Golgi tendon organs (GTOs) are firing action potentials? OR “What is the GTO reflex?” 1. GTOs serve as "safety devices" that help prevent excessive force during muscle contraction 2. Inhibitory influences of the GTO could be gradually reduced in response to strength training (Exercise Physiology, Powers & Howley, 4th ed, 2001) Similar statements in: Exercise Physiology, Brooks, Fahey, White & Baldwin, 3rd ed, 2000 Biomechanics, Kreighbaum & Barthels, 4th ed, 1996 Fleck and Kraemer, Designing resistance training programs, 1997 Baechle & Earle (eds), Essentials of Strength Training and Conditioning, 2 nd ed, 2000 What do GTOs really do when they are activated by muscle tension? F r o m n e u r o p h y s i o l o g y r e s e a r c h a r t i c l e s 1) GTOs do not always inhibit the homonymous muscle. Ib afferents rarely inhibit ankle flexor motor neurons and inhibit only some extensor motor neurons (Eccles et al., J Physiol, 138:227,1957) 2) GTOs can excite the homonymous and heteronymous muscles Sample experimental results: “during walking Ib activity(force feedback) of (ankle) extensors can reinforce the ongoing extensor activity and prevent initiation of flexor activity.” (1,7,8,9) WHILE WALKING: in stance phase of locomotion when ankle extensor contracts, Ib firing excite
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