title: The relationship of the energetic cost of slow walking and peak energy expenditure to gait speed in mid-to-late life.
abstract: OBJECTIVE
  Peak energy expenditure is highly correlated with usual gait speed; however, it is unknown whether the energetic cost of walking is also an important contributor to usual gait speed when considered as a component of peak walking capacity.
  
  
  METHODS
  The energetic cost of 5 mins of slow treadmill walking (0.67 m/sec), peak overground walking energy expenditure, and usual gait speed over 6 m were assessed cross-sectionally in 405 adults aged 33 to 94 yrs in the Baltimore Longitudinal Study of Aging.
  
  
  RESULTS
  Mean (SD) energy expenditures during slow and peak sustained walking were 8.9 (1.4) and 18.38 (4.8) ml kg(-1) min(-1), respectively. Overall, the energetic cost of slow walking as a percentage of peak walking energy expenditure was strongly associated with usual gait speed (P < 0.001); however in stratified analyses, this association was maintained only in those with peak walking capacity below 18.3 ml kg(-1) min(-1) (P = 0.04), the threshold associated with independent living.
  
  
  CONCLUSIONS
  In older persons with substantially reduced peak walking capacity, the energetic cost of walking is associated with gait speed, particularly when peak walking capacity nears the minimum level considered necessary for independent living. Thus, optimal habilitation in older frail persons may benefit from both improving fitness and reducing the energetic cost of walking.
authors.affiliation: Longitudinal Studies Section, Clinical Research Branch, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, USA.
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Schrack
authors.forename: Eleanor M
authors.initials: EM
authors.lastname: Simonsick
authors.forename: Luigi
authors.initials: L
authors.lastname: Ferrucci
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D002153:Calorimetry, Indirect; D003430:Cross-Sectional Studies; D004734:Energy Metabolism / Q000502:physiology*; D005260:Female; D005684:Gait / Q000502:physiology*; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption / Q000502:physiology; D013997:Time Factors; D016138:Walking / Q000502:physiology*