Comparison of MTI Accelerometer Cut-points For Predicting Time Spent in Physical Activity
- Published on May 2003
The purpose of this study was to establish the accuracy of five published accelerometer regression equations that predict time spent in different intensity classifications during free-living activities.
Ten participants completed physical tasks in a field setting for a near-continuous 5 – 6 h-period while oxygen uptake and accelerometer data were collected. The amount of time spent in resting/light, moderate and hard activity was computed from 3 and 6 MET cut-points associated with five existing regression formulas relating accelerometer counts·min-1 to energy expenditure.
The Freedson cut-points over-estimated resting/light activity by 34 min (13%) and under-estimated moderate activity by 38 min (60%). The Hendelman cut-points for all activities underestimated resting/light activity by 77 min (29%), and overestimated moderate activity by 77 min (120%). The Hendelman cut-points developed from walking activities over-estimated resting/light activity by 37 min (14%) and under-estimated moderate activity by 38 min (60%). Estimates from the Swartz cut-points for estimating time spent in resting/light, moderate and hard intensity activity were not different from the criterion measure. The Nichols cut-points over-estimated resting/light activity by 31 min (12%) and under-estimated moderate activity by 35 min (55%). Even though the Swartz method did not differ from measured time spent in moderate activity on a group basis, on an individual basis, large errors were seen. This was true for all regression formulas. These errors highlight some of the limitations to using hip-mounted accelerometers to reflect physical activity patterns.
The finding that different accelerometer cut-points gave substantially different estimates of time spent data has important implications for researchers using accelerometers to predict time spent in different intensity categories.
Link to Abstract: http://www.ncbi.nlm.nih.gov/pubmed/12784173
- Strath, S. J.
- Bassett, D. R. Jr
- Swartz, A. M.
International Journal of Sports Medicine