The mechanics of running while approaching and jumping over an obstacle

Abstract

When leaping an obstacle, the runner increases the vertical velocity of his/her centre of mass (COM) at takeoff to augment the amplitude and duration of the aerial phase over it. This study analyses the modification of the bouncing mechanism of running when approaching a barrier. The forces exerted by the feet on the ground are measured by a 13-m-long force platform during the four to nine running steps preceding the jump over a 0.45- to 0.85-m-high barrier, at an approaching speed between 9 and 21 km h(-1). The movements of the COM are evaluated by time-integration of the forces and the stiffness of the bouncing system by computer simulation. The running mechanism is modified during the two steps preceding the barrier. During the contact period, two steps before the barrier, the leg-spring stiffness decreases; consequently, the COM is lowered and accelerated forward. Then during the contact period preceding the obstacle, the leg-spring stiffness increases and the COM is raised and accelerated upwards, whereas its forward velocity is reduced. During this phase, the leg-spring acts like a pole, which stores elastic energy and changes the direction of the velocity vector to release this energy in a vertical direction. At high speeds, this storage-release mechanism of elastic energy is sufficient to provide the energy necessary to leap the obstacle. On the contrary, at low speeds, the amount of elastic energy stored and released in the leg-spring is not sufficient to jump over the obstacle and additional positive muscular work must be done.

The rebound of the body during uphill and downhill running at different speeds

“…The fact that E ext decreases shows that the loss in E f is greater than the gain in E v ; part of the E ext lost is stored in the elastic element of the MTU to be released during the second part of contact to increase the kinetic and potential of the COM. Note that the same phenomenon during the running step preceding the jump over an obstacle was described by Mauroy et al (2013).…”

Determinants of optimal leg use strategy: horizontal to vertical transition in the parkour wall climb

“…A distinctively horizontal TD trajectory entering the beginning of the transition is used by both the model and the participants, and is followed by a much steeper angle at TO from the ground. This asymmetrical trajectory has been observed in individuals jumping over obstacles during running (Mauroy et al, 2013). Also common between the model and participants is the use of a leg angle above horizontal at wall contact.…”

Kinematic primitives for walking and trotting gaits of a quadruped robot with compliant legs

“…As mentioned earlier, animals feature components of (simple) in-series leg compliance (Alexander, 1984; Gregersen et al, 1998). This morphological feature works also well for robots.…”

“…Physical, biological leg compliance was found to function as energy recoil mechanism, allowing animals to re-use negative work, and reduce metabolic cost of locomotion (Alexander, 1984, 1990, 1991; Biewener and Blickhan, 1988). Sources of compliance were found both in muscles and muscle complexes (Witte et al, 1994; Labeit and Kolmerer, 1995; Wilson et al, 2003), and in tendons and aponeuroses (Alexander, 1977; Witte et al, 1997; Biewener, 1998; Gregersen et al, 1998; Lichtwark et al, 2007).…”