Watching the grainy movie images of Neil Armstrong and Buzz Aldrin skipping light-footed across the surface of the Moon, it is clear that reducing the effect of gravity dramatically alters how we walk and run. Delyle Polet, from the University of Calgary, says ‘a person should be able to take higher leaps in running’, as the runner is released from the effects of gravity. However, when Polet and colleagues Ryan Schroeder and John Bertram asked 10 young volunteers to run in a harness that reduced the strength of gravity on their bodies, they were surprised that instead of bobbing higher up, the bounce seemed to be taken out of the runners’ strides. ‘This gait modification seems paradoxical’, says Polet.

Thinking the problem through, Bertram, Schroeder and Polet reasoned that people running with a flatter trajectory in low gravity might push off from the ground more slowly; this would allow them to save energy with each push. In addition, they should be able to remain aloft for longer than they would in normal gravity, providing more time to swing their legs with ease. And, when the trio analysed the volunteers’ movements, it was clear that they were pushing off more slowly, while also taking significantly longer strides.

However, Polet says that it is still unclear why the Apollo astronauts tended to skip instead of run, and how runners would move at lower and higher speeds in low gravity. ‘We hope to investigate these questions with further experiments, as well as more sophisticated, predictive energetic models’, he says.

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R. T.
J. E. A.
Reducing gravity takes the bounce out of running
J. Exp. Biol.