Energy transfer mechanisms as a compensatory strategy in below knee amputee runners

Czerniecki, Joseph M.; Gitter, Andrew; Beck, James C.

doi:10.1016/0021-9290(95)00173-5

Cited by 40 publications

References 12 publications

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“…The decrease of external work is overestimated because of disregarding the work done to move the snow sideways, a negligible component in DP from normal than do those of the latter. Below-knee amputees can run, and in many of them the locomotor patterns are not very different from normal (Enoka et al 1982); however the work done by the intact limb is 30% greater than that done by a limb of a normal subject, while the work done by the prosthetic limb is substantially equal (Czerniecki et al 1996). An increased energy transfer across the hip joint to the trunk during the swing phase can in part compensate for this difference.…”

Section: Enhanced Leg Locomotionmentioning

confidence: 97%

Biomechanical and physiological aspects of legged locomotion in humans

Saibene¹,

2003

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Walking and running, the two basic gaits used by man, are very complex movements. They can, however, be described using two simple models: an inverted pendulum and a spring. Muscles must contract at each step to move the body segments in the proper sequence but the work done is, in part, relieved by the interplay of mechanical energies, potential and kinetic in walking, and elastic in running. This explains why there is an optimal speed of walking (minimal metabolic cost of about 2 J.kg(-1).m(-1) at about 1.11 m.s(-1)) and why the cost of running is constant and independent of speed (about 4 J.kg(-1).m(-1)). Historically, the mechanical work of locomotion has been divided into external and internal work. The former is the work done to raise and accelerate the body centre of mass (m) within the environment, the latter is the work done to accelerate the body segments with respect to the centre of m. The total work has been calculated, somewhat arbitrarily, as the sum of the two. While the changes of potential and kinetic energies can be accurately measured, the contribution of the elastic energy cannot easily be assessed, nor can the true work performed by the muscles. Many factors can affect the work of locomotion--the gradient of the terrain, body size (height and body m), and gravity. The partitioning of positive and negative work and their different efficiencies explain why the most economical gradient is about -10% (1.1 J.kg(-1).m(-1) at 1.3 m.s(-1) for walking, and 3.1 J.kg(-1).m(-1) at between 3 and 4 m.s(-1) for running). The mechanics of walking of children, pigmies and dwarfs, in particular the recovery of energy at each step, is not different from that of taller (normal sized) individuals when the speed is expressed in dynamically equivalent terms (Froude number). An extra load, external or internal (obesity) affects internal and external work according to the distribution of the added m. Different gravitational environments determine the optimal speed of walking and the speed of transition from walking to running: at more than 1 g it is easier to walk than to run, and it is the opposite at less than 1 g. Passive aids, such as skis or skates, allow an increase in the speed of progression, but the mechanics of the locomotion cannot be simply described using the models for walking and running because step frequency, the proportion of step duration during which the foot is in contact with the ground, the position of the limbs, the force exerted on the ground and the time of its application are all different.

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Section: Enhanced Leg Locomotionmentioning

confidence: 97%

Biomechanical and physiological aspects of legged locomotion in humans

Saibene¹,

2003

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“…RSP allow considerable elastic energy return (Brü ggemann et al 2008) and thus emulate the spring-like behaviour of biological limbs during running (Ker et al 1987). However, unlike biological legs, passive prostheses cannot generate mechanical power de novo (Czerniecki et al 1996), nor can the prosthesis' stiffness be varied while running. At top speed, Oscar Pistorius had 22 per cent lower stance average vertical GRF than performance-matched intact sprinters (Weyand et al 2009).…”

Section: Introductionmentioning

confidence: 99%

Running-specific prostheses limit ground-force during sprinting

et al. 2009

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Running-specific prostheses (RSP) emulate the spring-like behaviour of biological limbs during human running, but little research has examined the mechanical means by which amputees achieve top speeds. To better understand the biomechanical effects of RSP during sprinting, we measured ground reaction forces (GRF) and stride kinematics of elite unilateral trans-tibial amputee sprinters across a range of speeds including top speed. Unilateral amputees are ideal subjects because each amputee's affected leg (AL) can be compared with their unaffected leg (UL). We found that stance average vertical GRF were approximately 9 per cent less for the AL compared with the UL across a range of speeds including top speed (p < 0.0001). In contrast, leg swing times were not significantly different between legs at any speed (p 5 0.32). Additionally, AL and UL leg swing times were similar to those reported for non-amputee sprinters. We infer that RSP impair force generation and thus probably limit top speed. Some elite unilateral trans-tibial amputee sprinters appear to have learned or trained to compensate for AL force impairment by swinging both legs rapidly.

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“…This causes the hip to move through a greater range of motion, which allows the athlete to lift the prosthesis through the swing phase. 10 However, this action is in direct contrast to what sprinting coaches teach their able-bodied sprinters, because it increases vertical force production while decreasing horizontal force production ( Table 1).…”

Section: Biomechanicsmentioning

confidence: 94%