Predicting Physical Activity Energy Expenditure in Manual Wheelchair Users

Purpose To assess the influence of anatomical placement of an accelerometer on physical activity energy expenditure (PAEE) prediction in manual wheelchair users.

Methods Ten accelerometer units (Actigraph GT3X+) were attached to a multi-axis shaker table and subjected to a sinusoidal oscillation procedure to assess mechanical validity and reliability. Fifteen manual wheelchair users (mean +/- SD, age: 36 +/- 11 years, body mass: 70 +/- 12 kg) then completed five activities, including deskwork and wheelchair propulsion (2, 4, 6, 8 km.hr-1). Expired gases were collected throughout. GT3X+ accelerometers were worn on the right wrist, upper arm and waist. The relationships between physical activity counts (PAC) and metabolic rate were subsequently assessed and bias +/- 95% limits of agreement (LoA) calculated.

Results During mechanical testing, CV ranged from 0.2 to 4.7% (intra-unit) and 0.9 to 5.2% (inter-unit) in all axes. During human exercise testing, PAC at each anatomical location was significantly (P < 0.01) correlated with metabolic rate (wrist; r = 0.93, upper arm; r = 0.87, waist; r = 0.73). The SEE for each correlation was 3.34, 4.38, and 6.07 kJ.min-1 for wrist, upper arm and waist, respectively. The absolute bias +/- 95% LoA values were 0.0 +/- 6.5 kJ.min-1, 0.0 +/- 8.5 kJ.min-1 and 0.0 +/- 11.8 kJ.min-1 for wrist, upper arm and waist, respectively.

Conclusion The Actigraph GT3X+ is a reliable tool for determining mechanical movements within the physiological range of human movement. Of the three anatomical locations considered, a wrist-mounted accelerometer explains more of the variance and results in the lowest random error when predicting PAEE in manual wheelchair users.