Leg muscles design: the maximum dynamic output hypothesis.

It is well known that both individual muscle and muscle groups produce maximum power against particular external loads. Within the present review, we propose the hypothesis that the lower-limb muscles of physically active individuals are predominantly designed to provide the maximum dynamic output (MDO; assessed as power and momentum) in rapid movements like jumping and sprinting against the load imposed by the weight and the inertia of their own body. The evidence supporting the MDO hypothesis can be found in some general considerations (e.g., certain evolutionary aspects, muscular system design in animals, effects of athletic training) as well as in recent experimental findings. Specifically, here we show that the optimal load for the power and momentum production in vertical jumping in habitually active individuals (but not in strength/power-trained athletes) could be the subject's own body. This also implies that the performance of rapid movements corresponds to body-size-independent MDO of the lower-limb muscles. If supported by future research, MDO hypothesis could 1) provide a theoretical framework for relating both structure and function of the muscular system and for understanding long-term adaptation of the muscular system; 2) suggest that rapid movements, such as vertical jumps, performed without external load could be used for the assessment of MDO (power and momentum) of lower limbs in nonathletic population; and 3) simplify the assessment of physical abilities and neuromuscular function in general through the usage of simple and relatively inexpensive physical performance tests based on natural rapid movements.