ActivPAL accuracy in determining metabolic rate during walking, running and cycling

To evaluate the ActivPAL's (AcP) ability to estimate METs during walking, running and cycling. Twenty physically active participants performed two submaximal exercises using a treadmill and cycle ergometer. The treadmill session involved varying speeds with a fixed grade and varying grade at fixed walking and running speeds. The cycling session involved fixed power, while cadence was varied and fixed cadence, while power was varied. Four AcPs (two AcP3 & two AcP4) were worn. ActivPAL MET estimations were compared to METS determined via indirect calorimetry. The AcP MET estimations between units and models did not differ. The AcP underestimated (-15% to -61%) METs with increasing speed and was unable to detect an increase in metabolic rate with a change in grade for walking and running. The AcP underestimated (-33% to -60%) METs during cycling and was unable to detect increases in metabolic rate when cadence was fixed, while power increased. The AcP can identify when exercise occurs and provides consistent information across units/models. However, the current AcP algorithm does not provide accurate estimates of METs during walking, running and cycling in a controlled laboratory setting, which would suggest limited accuracy in the field.