Effect of the pull-down force magnitude on the external work during running in weightlessness on a treadmill

Gosseye, Thierry;Heglund, Norman;Willems, Patrick
(2008) 4th European Conference of the International Federation for Medical and Biological Engineering - ECIFMBE 2008 — Location: Antwerp, Belgium (23.November.2008)

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  • Gosseye, Thierryorcid-logoUCLouvain
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  • Heglund, NormanUCLouvain
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  • Willems, PatrickUCLouvain
    Author
Abstract
Astronauts exposed to extended periods of weightlessness perform exercises to prevent bone decalcification and muscular atrophy. One of the countermeasures is running on a treadmill equipped with a subject loading system that simulates gravity. The bone stress and muscular work generated during this exercise are important physiological cues for maintaining bone and muscular mass. Unfortunately, in space this exercise is sufficiently uncomfortable that astronauts use a pull-down force equivalent to only about half of their weight on Earth. In this study, we compare the mechanics of running at zero g with a pull-down force of body weight to running at zero g with a pull-down force of half body weight. We designed a treadmill that incorporates force transducers and a loading system. The external work required to maintain the movements of the center of mass of the body relative to the surroundings was calculated from the measured ground reaction forces. Experiments were conducted during a ESA parabolic flight campaign. We analyzed 614 steps from two subjects running in weightlessness on the treadmill at 2 and 3m s/sup -1/ at 0.5g and 1g simulated gravity. Bone stress is reduced at 0.5g relative to lg, since the maximal ground reaction force decreases by 19-36%. Hypogravity also decreases the external work done each step by 3143%. Although the time of contact does not change dramatically at 0.5g compared to 1g (-15% to +10%), the aerial phase is increased by 82-131%. Since, at a given speed, the work done each step is reduced and the step length is increased, the external work per unit distance is decreased by 45-57%. Therefore, as compared to running on Earth, running on a treadmill in space at 0.5g reduces bone stress and muscular work by 20-60%. Consequently the physiological benefits of this exercise are likely to be less than desired.
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Gosseye, T., Heglund, N., & Willems, P. (2008). Effect of the pull-down force magnitude on the external work during running in weightlessness on a treadmill. In Vander Sloten, J.; Nyssen, M.; Verdonck, P.; Haueisen, J.; (ed.), 4th European Conference of the International Federation for Medical and Biological Engineering - ECIFMBE 2008 (p. p. 2116-2119). Springer verlag. https://hdl.handle.net/2078.5/228964