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Table 3 Effect of activity monitor removals during sleep on the prediction of physical activity and total energy expenditure.

From: Estimates of adherence and error analysis of physical activity data collected via accelerometry in a large study of free-living adults

  Physical Activity
  counts·min-1·day-1 log (counts·min-1·day-1)
Simulation Mean (SD) CV (%) Mean (SD) CV (%)
24 HR 228.4 (97.2) - 5.35 (0.40) -
A1 220.5 (97.6)* 3.1 5.30 (0.45)* 0.7
B1 332.9 (151.3)* 26.0 5.71 (0.43)* 4.8
C1 228.2 (98.8) 1.6 5.35 (0.42) 0.3
  Total Energy Expenditure
  MJ·day-1 log (MJ·day-1)
Simulation Mean (SD) CV (%) Mean (SD) CV (%)
24 HR 11.2 (3.3) - 2.38 (0.29) -
A1 11.2 (2.8) 9.0 2.37 (0.24) 4.1
B1 11.8 (4.2) 9.9 2.41 (0.26) 4.0
C1 11.2 (2.9) 9.0 2.38 (0.24) 4.0
  1. *p < 0.05 vs. 24 HR
  2. 24 HR: physical activity data from subset of highly adherent subjects (n = 35). Simulation A1: simulation of activity monitor removal during sleep by imputing zeroes. Simulation B1: simulation of compensating for activity monitor removal during sleep by measuring waking hours only (sleeping physical activity deleted). Simulation C1: simulation of compensating for activity monitor removal during sleep by imputing a constant (23.1 counts/min) CV(%)= coefficient of variation = ((standard deviation of 24 HR – Simulation A1/B1/C1)/(mean of 24 HR and Simulation A1/B1/C1)) × 100.