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It is known that muscular force is reduced in old age. We investigate what are the effects of this phenomenon on the mechanics of running. We hypothesized that the deficit in force would result in a lower push, causing reduced amplitude of the vertical oscillation, with smaller elastic energy storage and increased step frequency. To test this hypothesis, we(More)
The landing-take-off asymmetry of running was thought to derive from, or at least to be consistent with, the physiological property of muscle to resist stretching (after landing) with a force greater than it can develop during shortening (before take-off). In old age, muscular force is reduced, but the deficit in force is less during stretching than during(More)
In an ideal elastic bounce of the body, the time during which mechanical energy is released during the push equals the time during which mechanical energy is absorbed during the brake, and the maximal upward velocity attained by the center of mass equals the maximal downward velocity. Deviations from this ideal model, prolonged push duration and lower(More)
During walking, the centre of mass of the body moves like that of a 'square wheel': with each step cycle, some of its kinetic energy, E(k), is converted into gravitational potential energy, E(p), and then back into kinetic energy. To move the centre of mass, the locomotory muscles must supply only the power required to overcome the losses occurring during(More)
The bouncing mechanism of human running is characterized by a shorter duration of the brake after 'landing' compared with a longer duration of the push before 'takeoff'. This landing-takeoff asymmetry has been thought to be a consequence of the force-velocity relation of the muscle, resulting in a greater force exerted during stretching after landing and a(More)
Human running at low and intermediate speeds is characterized by a greater average force exerted after 'landing', when muscle-tendon units are stretched ('hard landing'), and a lower average force exerted before 'takeoff', when muscle-tendon units shorten ('soft takeoff'). This landing-takeoff asymmetry is consistent with the force-velocity relation of the(More)
Step frequency and energy expenditure are greater in backward running than in forward running. The differences in the motion of the centre of mass of the body associated with these findings are not known. These differences were measured here on nine trained subjects during backward and forward running steps on a force platform at 3-17 km h(-1). In contrast(More)
A long-lasting challenge in comparative physiology is to understand why the efficiency of the mechanical work done to maintain locomotion increases with body mass. It has been suggested that this is due to a more elastic step in larger animals. Here, we show in running, hopping and trotting animals, and in human running during growth, that the resonant(More)
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