The Application of Neuromuscular Electrical Stimulation Training in Various Non-neurologic Patient Populations: A Narrative Review

In the last 2 decades, neuromuscular electrical stimulation has been used increasingly in deconditioned patients with the aim of increasing muscle force. Much basic research has been conducted in the area of increasing a muscle's fatigue resistance by neuromuscular electrical stimulation but similarly thorough research with regard to increasing maximal force is missing. Insufficient clinical and basic knowledge exists on the selection of stimulation parameters that will optimize muscle hypertrophy and gains in muscle force. For volitional training, established stimuli for muscle hypertrophy (which more or less parallels maximal muscle force) are muscle tension, metabolic stress, and muscle damage. The present review summarizes findings from clinical and basic research in terms of muscle mechanical as well as acute and chronic physiologic effects of different stimulation protocols, explains the role of the various stimulation parameters in determining the effect of NMES training protocols, and gives clinical recommendations for the choice of stimulation parameters for different patient populations with different training goals, such as increasing muscle force, mass, endurance, or energy consumption. We limit this review to non-neurologic patients, because training goals of neurologic patients are specific to their functional deficits.