Meeting Abstract
It is clear that humans have a speed at which their energetic costs are minimized when traveling a given distance, either when running or walking. Early studies further showed that humans chose to walk at their optimum speed, when walking alone, unburdened, and on a level surface. In recent years, a variety of studies looking at various perturbations of the original walking work have suggested there are nuances pertaining to human choice, particularly when tasks increase in difficulty as well as when people are walking with others. “Increase in difficulty” appears to be anything that makes the overall cost of transport (CoT) curve increase or shift—for example, walking on an incline, running, carrying a burden, and being of an increased mass. When humans walk on inclines and are of larger body masses, they are more likely to choose a speed closer to the optimum speed as their preference—this is reasonable because both the CoT curvature is more acute (so penalties for moving away from the optimum are increased) as well as because the overall cost is high. Interestingly, while carrying novel burdens, females seem to have an ability to deviate from the optimum speed; this may be due to changes in thermoregulation, kinematic cues, as well as to the fact that females have a broader CoT curvature generally. These preferences can shift in the context of group walking however; whereas females seem more likely to maintain optimality when walking with other females, their speed increases when walking with (larger, faster) males. Males conversely change their speeds continually when walking with others—speeding up when walking with other men and slowing down to various degrees when walking with females. Thus, the social dynamics of walking are such that physiological and kinematic cues can be ignored, at least for a time.
