title: Anomalous centre of mass energy fluctuations during treadmill walking in healthy individuals.
abstract: Motorised treadmills are used to research and rehabilitate gait despite conflicting evidence that treadmill ambulation is equivalent to ground walking. It has been suggested that no mechanical differences should exist between these environments but there is little evidence to support this. During ground walking, the whole body centre of mass (COM) acts like an inverted pendulum recovering energy, thereby reducing the effort of locomotion. The energy recovery has a relationship with speed whereby maximum recovery occurs at intermediate speeds. In order to determine the relationship between energy recovery and speed during treadmill walking, we investigated estimated COM displacement in nine healthy individuals each walking on a treadmill at seven different speeds. In addition, we measured oxygen cost to determine the effort of walking. Our participants formed two distinct groups, those with normal COM energy recovery (N%R) that was similar to ground walking, and those with low COM energy recovery (L%R) that was different from typical ground walking. The low energy recovery in the L%R group was attributed to in-phase potential and kinetic energy fluctuations. Despite the low energy recovery values both groups produced the expected 'U'-shaped oxygen cost speed curve with no significant difference between groups (p<0.05), however, only N%R produced a significant relationship between energy recovery and oxygen cost (p<0.05). Although a useful tool, walking on a treadmill may not be a true representation of ground walking and therefore not the most effective way to research or rehabilitate gait.
authors.affiliation: Movement Science Group, School of Life Sciences, Oxford Brookes University, Headington, United Kingdom. jcollett@brookes.ac.uk
authors.forename: Johnathan
authors.initials: J
authors.lastname: Collett
authors.forename: Helen
authors.initials: H
authors.lastname: Dawes
authors.forename: Ken
authors.initials: K
authors.lastname: Howells
authors.forename: Charlotte
authors.initials: C
authors.lastname: Elsworth
authors.forename: Hooshang
authors.initials: H
authors.lastname: Izadi
authors.forename: Cath
authors.initials: C
authors.lastname: Sackley
mesh_terms: D000328:Adult; D015444:Exercise / Q000502:physiology*; D005260:Female; D005684:Gait / Q000502:physiology*; D006801:Humans; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology; D016138:Walking / Q000502:physiology*