[Current knowledge on muscle training: endurance and strength yield complementary effects]

Both endurance and strength training are generally agreed to be necessary components of a balanced fitness programme. These two types of training are complementary; strength training improves neuromuscular function, prevents injuries, and is a prerequisite for effective endurance training. Whereas endurance training results in high energy expenditure during exercise, strength training, being associated with increased muscle mass, may result in increased energy expenditure at rest. In conjunction with endurance training, the most striking finding in skeletal muscle is its remarkable adaptability. Indeed, it is usually possible for the muscles to acquire the characteristics necessary to meet prevailing functional demands. This is true even if the demand is continuous contractile activity, 24 hours a day, week after week. The physiological effects of strength training are the result of hypertrophy of individual motor units, mostly comprising type II (fast-twitch) fibres, but are also secondary to neural changes affecting the recruitment and frequency modulation of motor units and co-ordination.