Simple calibration procedures like step and walk tests captured 59-76% of between-individual variance in physical activity intensity, compared to >95% for reference treadmill calorimetry (P<0.001).
Observational (n=51)
Do less burdensome individual calibration procedures for heart rate and accelerometry accurately measure physical activity intensity compared to a reference calibration procedure with indirect calorimetry?
Simple calibration procedures for heart rate and accelerometry capture a substantial proportion of between-individual variance in physical activity intensity, making them feasible for large epidemiological studies.
p-value: p=<0.001
Combining accelerometry with heart rate (HR) monitoring may improve precision of physical activity measurement. Considerable variation exists in the relationships between physical activity intensity (PAI) and HR and accelerometry, which may be reduced by individual calibration. However, individual calibration limits feasibility of these techniques in population studies, and less burdensome, yet valid, methods of calibration are required. We aimed to evaluate the precision of different individual calibration procedures against a reference calibration procedure: a ramped treadmill walking-running test with continuous measurement of PAI by indirect calorimetry in 26 women and 25 men mean (SD): 35 (9) yr, 1.69 (0.10) m, 70 (14) kg. Acceleration (along the longitudinal axis of the trunk) and HR were measured simultaneously. Alternative calibration procedures included treadmill testing without calorimetry, submaximal step and walk tests with and without calorimetry, and nonexercise calibration using sleeping HR and gender. Reference accelerometry and HR models explained >95% of the between-individual variance in PAI (P < 0.001). This fraction dropped to 73 and 81%, respectively, for accelerometry and HR models calibrated with treadmill tests without calorimetry. Step-test calibration captured 62-64% (accelerometry) and 68% (HR) of the variance between individuals. Corresponding values were 63-76% and 59-61% for walk-test calibration. There was only little benefit of including calorimetry during step and walk calibration for HR models. Nonexercise calibration procedures explained 54% (accelerometry) and 30% (HR) of the between-individual variance. In conclusion, a substantial proportion of the between-individual variance in relationships between PAI, accelerometry, and HR is captured with simple calibration procedures, feasible for use in epidemiological studies.
Brage et al. (2007) conducted an observational in Physical activity measurement (n=51). Alternative calibration procedures (step, walk, nonexercise tests) vs. Ramped treadmill walking-running test with indirect calorimetry was evaluated on Between-individual variance in physical activity intensity explained by the models (p=<0.001). Simple calibration procedures like step and walk tests captured 59-76% of between-individual variance in physical activity intensity, compared to >95% for reference treadmill calorimetry (P<0.001).