2 2 C H A P T E R Neuromuscular Anatomy and Adaptations to Conditioning

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 EventType IType II 100-m sprintLowHigh 800-m runHighHigh MarathonHighLow Olympic weightliftingLowHigh Barbell squatHighHigh SoccerHighHigh Field hockeyHighHigh Football wide receiverLowHigh Football linemanHighHigh BasketballLowHigh Distance cyclingHighLow

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. 

Muscle Spindle

Golgi Tendon Organ

Table 2.3 Major Adaptations to Resistance Versus Aerobic Endurance Training VariableResistanceAerobic trainingendurance training Size of muscleIncreaseNo change fibers Number of muscleNo changeNo change fibers Movement speedIncreaseNo change StrengthIncreaseNo change Aerobic capacityNo changeIncrease Anaerobic capacityIncreaseNo 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. 