Objectives: We aimed to investigate accelerometer output corresponding to physical activity intensity cut-points based on percentage of peak oxygen consumption (%VO2peak) and Metabolic Equivalent of Task (MET) value in women treated for breast cancer. Design: Laboratory study. Methods: Fifty female patients shortly after completion of treatment for breast cancer were included. VO2peak was determined during a cardiopulmonary exercise test. Subsequently, patients performed ten activities with different intensities while wearing an accelerometer on the right hip and a mobile oxycon to assess oxygen consumption. We studied the relationship between energy expenditure (expressed as %VO2peak and MET-value) and accelerometer output (in counts per minute (cpm)) with linear regression analyses. We determined accelerometer output corresponding to physical activity intensity cut-points (40% and 60%VO2peak; 3 and 6 MET) using regression equations. Results: VO2peak was 22.4 mL/kg/min (SD 5.2) and resting metabolic rate was 3.1 mL/kg/min (SD 0.6). Accelerometer output corresponding to the cut-points for moderate (40% VO2peak) and vigorous intensity (60% VO2peak) were 1123 and 1911, respectively. The analyses based on MET-values resulted in accelerometer output of 1189 cpm for the moderate (3 MET) and 2768 cpm for the vigorous intensity cut-point (6 MET). Conclusions: Accelerometer outputs for moderate and vigorous intensity physical activity were lower than commonly used cut-points (i.e. 1952 and 5724 cpm), irrespective of the method used to express energy expenditure (%VO2peak versus MET-value). Thus, categorizing physical activity intensities based on general-population cut-points, may underestimate physical activity intensities for women treated for breast cancer.
Sweegers, M. G., Buffart, L. M., Huijsmans, R. J., Konings, I. R., van Zweeden, A. A., Brug, J., ... Altenburg, T. M. (2020). From accelerometer output to physical activity intensities in breast cancer patients. Journal of Science and Medicine in Sport, 23(2), 176-181. https://doi.org/10.1016/j.jsams.2019.09.001