title: Body Acceleration as Indicator for Walking Economy in an Ageing Population.
abstract: BACKGROUND
  In adults, walking economy declines with increasing age and negatively influences walking speed. This study aims at detecting determinants of walking economy from body acceleration during walking in an ageing population.
  
  
  METHODS
  35 healthy elderly (18 males, age 51 to 83 y, BMI 25.5±2.4 kg/m2) walked on a treadmill. Energy expenditure was measured with indirect calorimetry while body acceleration was sampled at 60Hz with a tri-axial accelerometer (GT3X+, ActiGraph), positioned on the lower back. Walking economy was measured as lowest energy needed to displace one kilogram of body mass for one meter while walking (WCostmin, J/m/kg). Gait features were extracted from the acceleration signal and included in a model to predict WCostmin.
  
  
  RESULTS
  On average WCostmin was 2.43±0.42 J/m/kg and correlated significantly with gait rate (r2 = 0.21, p<0.01) and regularity along the frontal (anteroposterior) and lateral (mediolateral) axes (r2 = 0.16, p<0.05 and r2 = 0.12, p<0.05 respectively). Together, the three variables explained 46% of the inter-subject variance (p<0.001) with a standard error of estimate of 0.30 J/m/kg. WCostmin and regularity along the frontal and lateral axes were related to age (WCostmin: r2 = 0.44, p<0.001; regularity: r2 = 0.16, p<0.05 and r2 = 0.12, p<0.05 respectively frontal and lateral).
  
  
  CONCLUSIONS
  The age associated decline in walking economy is induced by the adoption of an increased gait rate and by irregular body acceleration in the horizontal plane.
authors.affiliation: Department of Human Biology, Maastricht University, Maastricht, The Netherlands.
authors.forename: Giulio
authors.initials: G
authors.lastname: Valenti
authors.affiliation: Personal Health Solutions, Philips Research Laboratories, Eindhoven, The Netherlands.
authors.forename: Alberto G
authors.initials: AG
authors.lastname: Bonomi
authors.affiliation: Department of Human Biology, Maastricht University, Maastricht, The Netherlands.
authors.forename: Klaas R
authors.initials: KR
authors.lastname: Westerterp
mesh_terms: D000054:Acceleration; D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D005260:Female; D005684:Gait; D006801:Humans; D008297:Male; D008875:Middle Aged; D016138:Walking / Q000502:physiology*