A feedback-controlled treadmill (treadmill-on-demand) and the spontaneous speed of walking and running in humans

A feedback- controlled treadmill (treadmill-on-demand) and the sponta- neous speed of walking and running in humans. J Appl Physiol 95: 838–843, 2003. First published April 11, 2003; 10.1152/japplphysiol.00128.2003.—A novel apparatus, com- posed by a controllable treadmill, a computer, and an ultra- sonic range finder, is here proposed to help investigation of many aspects of spontaneous locomotion. The acceleration or deceleration of the subject, detected by the sensor and pro- cessed by the computer, is used to accelerate or decelerate the treadmill in real time. The system has been used to assess, in eight subjects, the self-selected speed of walking and run- ning, the maximum “reasonable” speed of walking, and the minimum reasonable speed of running at different gradients (from level up to 􏰁25%). This evidenced the speed range at which humans neither walk nor run, from 7.2 􏰂 0.6 to 8.4 􏰂 1.1 km/h for level locomotion, slightly narrowing at steeper slopes. These data confirm previous results, obtained indi- rectly from stride frequency recordings. The self-selected speed of walking decreases with increasing gradient (from 5.0 􏰂 0.8 km/h at 0% to 3.0 􏰂 0.9 km/h at 􏰁25%) and seems to be 􏰃30% higher than the speed that minimizes the meta- bolic energy cost of walking, obtained from the literature, at all the investigated gradients. The advantages, limitations, and potential applications of the newly proposed methodol- ogy in physiology, biomechanics, and pathology of locomotion are discussed in this paper.