PED 1323 Motor Control & Motor Learning

These results in the untrained limb are similar to

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These results in the untrained limb are similar to those seen in the first weeks of a strength training program, more force is exerted but with no hypertrophy. THE MECHANISMS FOR ABOVE STRENGTH INCREASES THAT ARE NOT PROPORTIONAL TO MUSCLE SIZE CHANGES MUST BE UNDERSTOOD, if we want to understand force production and training (to be answered below) 4) From Sale (1988) For the people who trained with a free squat: WHY is there less of an increase in knee extensor force under the different testing conditions using the same muscle? But… what exactly are the…“Neural adaptations to resistance training” that contribute to increased force production with training Neural adaptations likely to occur (based on study quality & quantity) in bold …. 1. Increased maximum EMG level seen, SOME studies in which MVC strength increases with training e.g. 3,4,9,12 , due to increased motor unit firing frequency , produces higher maximum force from muscle. Increases in neural drive are observed to be greater for lengthening contractions compared to shortening contractions 1 . See figures below BUT : a. Not all training studies show increased EMG with strength increases e.g., 9,13
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Motor Control Section 2: Muscles fibers types and their use Unit 6a: Neuromuscular adaptations with resistance training b. Increase in motor unit firing frequency with training has been found in only some studies 6, 9 c. Increase in maximal effort motor unit firing frequency with training has been found to be much higher in elderly & moderately higher in young adults 10 , OR has been found to occur in young, but NOT in elderly 11 . d. The use of surface EMG to measure muscle activation level (neural drive) has recently been questioned 4, 9 . 85% MVC FORCE EFFORT BEFORE RESISTANCE TRAINING HAS 100% RECRUIMENT (BUT LOW FIRING RATE IN LARGEST MOTOR UNITS) MAXIMUM FORCE EFFORT BEFORE RESISTANCE TRAINING 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 Force level being produced 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 85% MVC 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 MAXIMUM FORCE EFFORT AFTER RESISTANCE TRAINING 2. Increased RATE of rise of EMG at start of force development 1,2,4,6 (increased doublets in motor unit firing at start of contraction 1,6,9 , lower recruitment threshold for motor units so they are recruited earlier as force is increasing 9 ), produces increased maximum rate of force development .
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