Physiology and therapeutic implications of negative work. A review.

Energy efficiency is an important attribute of negative work (W neg). Eccentric muscle contractions characteristic of W neg can generate greater force at reduced oxygen cost and perceived exertion compared with concentric muscle contractions in positive work (W pos). Thus, activities incorporating W neg could have important implications in improving the functional capacity of an individual with limited physiologic reserves or ability to use these reserves. Other characteristics of W neg such as muscle trauma or soreness and increased total heat production and cutaneous blood flow, however, may be counter-therapeutic and even hazardous. The purpose of this review is to describe the physiology and therapeutic implications of W neg. Because the body of knowledge with respect to the therapeutic effects of W neg is relatively scant compared with W pos, clinical trials are needed to establish the indications, contraindications, possible limitations, guidelines for prescription, and therapeutic efficacy of W neg.