Light-intensity activities are important for estimating physical activity energy expenditure using uniaxial and triaxial accelerometers.

This study evaluated the validity of the total energy expenditure (TEE) estimated using uniaxial (ACCuni) and triaxial (ACCtri) accelerometers in the elderly. Thirty-two healthy elderly (64-87 years) participated in this study. TEE was measured using the doubly labeled water (DLW) method (TEE(DLW)). TEE(ACCuni) (6.79 +/- 1.08 MJ day(-1)) was significantly lower than TEE(DLW) (7.85 +/- 1.54 MJ day(-1)) and showed wider limits of agreement (-3.15 to 1.12 MJ day(-1)) with a smaller correlation coefficient (r = 0.703). TEE(ACCtri) (7.88 +/- 1.27 MJ day(-1)) did not differ from TEE(DLW) and showed narrower limits of agreement (-1.64 to 1.72 MJ day(-1)) with a larger correlation coefficient (r = 0.835, P < 0.001). The estimated intensities of light activities were significantly lower with ACCuni. Greater mediolateral acceleration was observed during 6-min walk tests. The results suggest that ACCtri is a better choice than ACCuni for assessing TEE in the elderly.