Physiological costs and temporo-spatial parameters of walking on a treadmill vary with body weight unloading and speed in both healthy young and older women

Walking on a treadmill with Body Weight Unloading (BWU), which has been successfully used on patients with neurological conditions, may also be used as a training tool to increase walking speed in healthy individuals. We hypothesised that BWU enables individuals to walk at a faster speed on a treadmill than they would do in normal gravity conditions without increasing their effort and with an increase in both stride length (SL) and stride frequency (SF). Oxygen uptake, heart rate (HR), SL and SF of six older women (mean ± SD; 70 ± 4 years) and six young women (26 ± 3 years) were measured during treadmill walking at three self-selected speeds (comfortable, slow and fast) and three different percentages of BWU (0, 20 and 40%). No significant differences were found between the groups in any self-selected walking speeds and any of the other variables. The combined data of the two groups showed that walking energy cost per unit of time (WECt) and HR at fast speed with 40% of BWU (258 ± 60 J kg⁻¹ min⁻¹ and 95 ± 15 beats min⁻¹, respectively) were similar to those measured at comfortable speed with no BWU (273 ± 47 J kg⁻¹ min⁻¹ and 101 ± 16 beats min⁻¹, respectively). Also SL and SF increased significantly with speed (P < 0.017) at any given percentage of BWU. The results suggest that 40% of BWU enables both young and older women to walk at a faster speed on a treadmill without increasing their effort and with an increase in both SL and SF.