Why is walker-assisted gait metabolically expensive?

Walker-assisted gait is reported to be ∼200% more metabolically expensive than normal bipedal walking. However, previous studies compared different walking speeds. Here, we compared the metabolic power consumption and basic stride temporal–spatial parameters for 10 young, healthy adults walking without assistance and using 2-wheeled (2W), 4-wheeled (4W) and 4-footed (4F) walker devices, all at the same speed, 0.30 m/s. We also measured the metabolic power demand for walking without any assistive device using a step-to gait at 0.30 m/s, walking normally at 1.25 m/s, and for repeated lifting of the 4F walker mimicking the lifting pattern used during 4F walker-assisted gait. Similar to previous studies, we found that the cost per distance walked was 217% greater with a 4F walker at 0.30 m/s compared to unassisted, bipedal walking at 1.25 m/s. Compared at the same speed, 0.30 m/s, using a 4F walker was still 82%, 74%, and 55% energetically more expensive than walking unassisted, with a 4W walker and a 2W walker respectively. The sum of the metabolic cost of step-to walking plus the cost of lifting itself was equivalent to the cost of walking with a 4F walker. Thus, we deduce that the high cost of 4F walker assisted gait is due to three factors: the slow walking speed, the step-to gait pattern and the repeated lifting of the walker.