The landing–take-off asymmetry of human running is enhanced in old age

Abstract

SUMMARYThe 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 shortening. The greater loss in concentric versus eccentric strength with aging led us to hypothesize that older versus younger adults would increase the landing-take-off asymmetry in running. To test this hypothesis, we measured the within-step changes in mechanical energy of the centre of mass of the body in old and young subjects. The difference between the peaks in kinetic energy attained during the fall and during the lift of the centre of mass is greater in the old subjects. The difference between the time to lift and accelerate the centre of mass (positive work) and to absorb the same amount of energy during the downward displacement (negative work) is also greater in the old subjects. Both these findings imply a difference in force between stretching and shortening during the bounce, which is greater in the old subjects than in the young subjects. This is qualitatively consistent with the more asymmetric force-velocity relation found in aged muscle and supports, even if does not prove, the hypothesis that the landing-take-off asymmetry in running derives from the different response of muscle to stretching and shortening.

Symmetry and Asymmetry in Bouncing Gaits

“…We hypothesized that the greater force exerted during stretching relative to shortening by aged muscle would increase the landing-takeoff asymmetry in running. As described below, this in fact what we found in experiments comparing the landing-takeoff asymmetry of eight old subjects (average age 73.6 ± 5.5 years) with that of eight young subjects (average age 20.8 ± 1.6) (36). Figure 22 and 23 show that the lift of the center of mass taking place in contact with the ground is greater in the old subjects than in the young subjects.…”

“…Old subject's curves are reproduced in grey on the right panel for comparison. Modified from [36]. Figure 24 shows that the ratio R int,down /R int,up is much larger in the old subject than in the young subject.…”

“…The procedure followed to determine the curves in Figure 6 and 7, and the external work, has been described in detail in several studies [34][35][36]. In short: the horizontal force and the vertical force minus the body weight were integrated electronically to determine the instantaneous velocity of the center of mass of the body to yield the instantaneous kinetic energy, E k = E kf + E kv .…”

“…The deviation from Blickhan's symmetrical model has recently been determined [36,58,59] by measuring the kinetic and the gravitational potential energy of the center of mass of the body during its lift and descent at each bouncing step (Figure 17). The aim of these experiments was to determine if and to what extent a possible different response of the muscle-tendons units to stretching and shortening affects the timing of negative and positive work performance during their stretchshortening cycles ( Figure 5).…”

Características fisiológicas e biomecânicas na corrida do triatlo: uma revisão narrativa

“…Os métodos para avaliação das determinantes fisiológicas e biomecânicas do desempenho não se modificaram, e este ponto abre um campo de novas possibilidades de análise para a corrida no triatlo. Por exemplo os avanços nos métodos de análise biomecânicos, como da determinação das assimetrias contato-despregue 52,53 e da determinação da eficiência mecânica, tendo em consideração a contra-parte anaeróbica no seu denominador, 54 e o trabalho mecânico interno no seu numerador. 55 Estas novas possibilidades podem melhorar a análise dos fatores determinantes fisiológicos e biomecânicos da corrida do triatlo.…”