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Introduction/Background: Accelerometers are a useful tool for the monitoring of physical activity (PA). The purpose of this study was to evaluate the accuracy of the ActiGraph GT3X+ in the estimation of EE according to the placement site during light moderate-intensity physical activities (PA) in healthy young and elderly.

Material and method: Fifty-six participants completed a single session of 3 PA. The PA included biking at 70 watt, walking at 4.6 km.h^-1, and running at 6.4 km.h^-1 for young and at 5.8 km.h^-1 for elderly. Each participant wore 5 triaxial accelerometers GT3X+ and a portable gas analyzer, used as the criterion measure. The GT3X+ were placed on the wrists (GT3X+ W), the hip (GT3X+ H) and the ankles (GT3X+ A). EE was estimated in Metabolic Equivalence Task (MET).

Results: The GT3X+ W and GT3X+ H largely underestimated EE, regardless the PA intensity (bias ≤ −40.0%; 1.2≤ ES ≤3.4). The GT3X+ A largely underestimated the EE during running (bias = −45.2%; ES=2.0). Conversely, the GT3X+ A very largely overestimated the EE during biking (bias = 514.8%; ES=2.1) and largely overestimated during walking (bias = 87.7%; ES=0.8).

Conclusion: The GT3X+ does not provide accurate EE estimates across a range of locations during light and moderate-intensity PA. This device has limitations and should be cautiously used during PA.