This chapter describes how the nervous system and neuromuscular structures function to control movement and how this understanding is important to developing training or rehabilitation strategies. A key element for success is a motivation to move based on intrinsic and extrinsic rewards initiated within structures of the prefrontal cortex, limbic system, basal ganglia, cerebellum, supplementary motor cortex and other cortical areas. Once initiated the excitation or inhibition of the corticospinal and motoneuronal systems will determine if an appropriate series of motor units are activated to effect the anticipated movement. The force output and movement control are implemented by an array of factors, such as recruitment, rate coding, synchronization, co-contractions, and other factors, which can be augmented or diminished by alterations associated with balance and stability, fatigue, injury, and other stressors. Based on these factors, suggestions are presented on how to plan training and rehabilitation strategies.