22C H A P T E R

Neuromuscular Anatomy and Adaptations to ConditioningNeuromuscular 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 UnitTwitch, 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.

Motor 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

The 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.

Proprioceptors are specialized sensory

receptors that provide the central nervous

system with information needed to maintain

muscle tone and perform complex coordinated

movements.

Muscle SpindleMuscle Spindle

Golgi TendonOrganGolgi TendonOrgan

Table 2.3 Major Adaptations to Resistance Versus Aerobic Endurance Training

Variable Resistance Aerobictraining endurance training

Size of muscle Increase No changefibers

Number of muscle No change No changefibers

Movement speed Increase No change

Strength Increase No change

Aerobic capacity No change Increase

Anaerobic capacity Increase No change

Adaptations to resistance training are

specific to the type of exercise performed.

Moreover, resistance training has no meaningful

impact on aerobic power.

Although 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.