title: Accelerometer output and its association with energy expenditure during manual wheelchair propulsion.
abstract: METHODS
  This is an experimental design.
  
  
  OBJECTIVE
  This study examined the association between rates of energy expenditure (that is, oxygen consumption (VO2)) and accelerometer counts (that is, vector magnitude (VM)) across a range of speeds during manual wheelchair propulsion on a motor-driven treadmill. Such an association allows for the generation of cutoff points for quantifying the time spent in moderate-to-vigorous physical activity (MVPA) during manual wheelchair propulsion.
  
  
  METHODS
  The study was conducted in the University Laboratory.
  
  
  METHODS
  Twenty-four manual wheelchair users completed a 6-min period of seated rest and three 6-min periods of manual wheelchair propulsion on a motor-driven wheelchair treadmill. The 6-min periods of wheelchair propulsion corresponded with three treadmill speeds (1.5, 3.0 and 4.5 mph) that elicited a range of physical activity intensities. Participants wore a portable metabolic unit and accelerometers on both wrists. Primary outcome measures included steady-state VO2 and VM, and the strength of association between VO2 and VM was based on the multiple correlation and squared multiple correlation coefficients from linear regression analyses.
  
  
  RESULTS
  Strong linear associations were established between VO2 and VM for the left (R=0.93±0.44; R2=0.87±0.19), right (R=0.95±0.37; R2=0.90±0.14) and combined (R=0.94±0.38; R2=0.88±0.15) accelerometers. The linear relationship between VO2 and VM for the left, right and combined wrists yielded cutoff points for MVPA of 3659 ±1302, 3630±1403 and 3644±1339 counts min(-1), respectively.
  
  
  CONCLUSIONS
  We provide cutoff points based on the linear association between energy expenditure and accelerometer counts for estimating time spent in MVPA during manual wheelchair propulsion using wrist-worn accelerometry. The similarity across wrist location permits flexibility in selecting a location for wrist accelerometry placement.
authors.affiliation: Department of Kinesiology and Community Health, University of Illinois at Urbana Champaign, Urbana, IL, USA.
authors.forename: Y C
authors.initials: YC
authors.lastname: Learmonth
authors.affiliation: Department of Kinesiology and Community Health, University of Illinois at Urbana Champaign, Urbana, IL, USA.
authors.forename: D
authors.initials: D
authors.lastname: Kinnett-Hopkins
authors.affiliation: Department of Kinesiology and Community Health, University of Illinois at Urbana Champaign, Urbana, IL, USA.
authors.forename: I M
authors.initials: IM
authors.lastname: Rice
authors.affiliation: Department of Kinesiology and Community Health, University of Illinois at Urbana Champaign, Urbana, IL, USA.
authors.forename: J L
authors.initials: JL
authors.lastname: Dysterheft
authors.affiliation: Department of Kinesiology and Community Health, University of Illinois at Urbana Champaign, Urbana, IL, USA.
authors.forename: R W
authors.initials: RW
authors.lastname: Motl
mesh_terms: D061725:Accelerometry / Q000295:instrumentation / Q000379:methods*; D000293:Adolescent; D000328:Adult; D001132:Arm / Q000503:physiopathology*; D004734:Energy Metabolism / Q000502:physiology*; D005080:Exercise Test; D006801:Humans; D009068:Movement; D010101:Oxygen Consumption / Q000502:physiology; D005082:Physical Exertion; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013223:Statistics as Topic; D014910:Wheelchairs; D055815:Young Adult