ABSTRACT
Standing on two legs is the exception rather than the rule in the animal kingdom. Animals that do stand on two legs normally exhibit anatomical adaptations to overcome the stability problems caused by bipedalism. The long tail of the kangaroo counterbalances its upper body weight when the animal moves and acts as a third leg when it is stationary. Modern humans exhibit interesting anatomical adaptations, notably the lumbar lordosis, to overcome the stability and energy requirements of erect bipedalism. Fatigue, when it does occur, is unlikely to be the result of increased cardiovascular load (Grandjean, 1980). Venous pooling, static loading of ligaments and compression of soft tissues are more likely causes of fatigue in standing. According to Hellebrandt (1938):
“Standing is cheap in terms of energy cost…. From this point of view, normal standing on both legs is almost effortless.”
