title: Overground vs. treadmill walking on biomechanical energy harvesting: An energetics and EMG study.
abstract: A biomechanical energy harvester is a wearable device that generates electricity from human motion. Walking on a treadmill has been used almost exclusively by researchers for studying the energetic effects of biomechanical energy harvesters and wearable robotics. A treadmill provides the advantage of having long duration trials within a stationary motion capture volume. However, no consensus exists on whether the results from treadmill walking accurately represent overground walking. We aim to investigate how a biomechanical energy harvester performs overground compared to on a treadmill by measuring energy expenditure and muscle activity. Participants (n=15) walked both overground and on a treadmill with and without a lower limb-driven biomechanical energy harvester. Energy expenditure was measured using indirect calorimetry and muscle activity was collected with surface electromyograms on seven superficial lower limb muscles. We observed a similar increase in metabolic cost of transport (Δoverground: 0.28±0.24J/kgm, Δtreadmill: 0.30±0.24J/kgm) from normal walking (overground: 2.56±0.33J/kgm, treadmill: 3.39±0.31J/kgm) to harvester walking (overground: 2.83±0.35J/kgm, treadmill: 3.69±0.32J/kgm) in both walking modes (p>0.05). This was accompanied a significant increase in muscle activity of select muscle groups (p<0.05). There was also a significant increase observed during walking on a treadmill compared to overground walking (p<0.05). In conclusion, our results suggest that although the metabolic cost of transport and muscle activation for treadmill walking is higher than that of overground, when studying the effects of a biomechanical energy harvester, treadmill will give similar net increases when compared to a controlled walking condition, such as normal walking, on the same walking surface.
authors.affiliation: Bio-Mechatronics and Robotics Laboratory Department of Mechanical and Materials Engineering Queen's University Kingston, Ontario K7K 4A4, Canada. Electronic address: 8jpm4@queensu.ca.
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Martin
authors.affiliation: Bio-Mechatronics and Robotics Laboratory Department of Mechanical and Materials Engineering Queen's University Kingston, Ontario K7K 4A4, Canada. Electronic address: ql3@queensu.ca.
authors.forename: Qingguo
authors.initials: Q
authors.lastname: Li
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D004576:Electromyography; D004734:Energy Metabolism / Q000502:physiology*; D005080:Exercise Test; D006801:Humans; D035002:Lower Extremity / Q000502:physiology*; D008297:Male; D016059:Range of Motion, Articular; D012016:Reference Values; D016138:Walking; D055815:Young Adult
keywords: EMG; Energy harvesting; Metabolic cost; Overground; Treadmill; Wearable robotics