2 C H A P T E R Neuromuscular Anatomy and Adaptations to Conditioning Robert T. Harris and Gary Dudley
Chapter Outline Neuromuscular anatomy and physiology Motor unit recruitment patterns during exercise Proprioception Neuromuscular adaptations to exercise
Twitch, Twitch Summation, and Tetanus of a Motor Unit (a) Single twitch, (b) force resulting from summation of two twitches, (c) unfused tetanus, and (d) fused tetanus.
M otor units are composed of muscle fibers with morphological and physiological characteristics that determine their functional capacity.
Table 2.2 Relative Involvement of Muscle Fiber Types in Sport Events Event Type I Type II 100-m sprint Low High 800-m run High High Marathon High Low Olympic weightlifting Low High Barbell squat High High Soccer High High Field hockey High High Football wide receiver Low High Football lineman High High Basketball Low High Distance cycling High Low
T he force output of a muscle can be varied by changing the number of activated motor units or by changing the frequency of activation of individual motor units.
P roprioceptors are specialized sensory receptors that provide the central nervous system with information needed to maintain muscle tone and perform complex coordinated movements.
Table 2.3 Major Adaptations to Resistance Versus Aerobic Endurance Training Variable Resistance Aerobic training endurance training Size of muscle Increase No change fibers Number of muscle No change No change fibers Movement speed Increase No change Strength Increase No change Aerobic capacity No change Increase Anaerobic capacity Increase No change
A daptations to resistance training are specific to the type of exercise performed. Moreover, resistance training has no meaningful impact on aerobic power.
A lthough aerobic endurance training increases aerobic power, it does not enhance muscle strength or size. In fact, intense aerobic endurance training can actually compromise the benefits of resistance training.