At some point in the future, if mankind hopes to settle planets outside the
Solar System, it will be crucial to determine the range of planetary conditions
under which human beings could survive and function. In this article, we apply
physical considerations to future exoplanetary biology to determine the
limitations which gravity imposes on several systems governing the human body.
Initially, we examine the ultimate limits at which the human skeleton breaks
and muscles become unable to lift the body from the ground. We also produce a
new model for the energetic expenditure of walking, by modelling the leg as an
inverted pendulum. Both approaches conclude that, with rigorous training,
humans could perform normal locomotion at gravity no higher than 4
gEarth.Comment: 12 pages, 4 figures, to be published in The Physics Teache