Evaluating the Validity of the SENS Motion® System for Measuring Physical Activity Intensity and Type Across Different Wear Locations

This study evaluated the validity of the SENS motion® system (SENS) for classifying activity intensity (sedentary, light, moderate-to-vigorous [MVPA]) and type (sedentary, standing, walking, running, cycling) across four wear locations: thigh, hip, non-dominant, and dominant wrist. In healthy adults (n = 62), SENS classifications were compared to activity intensity from compendium-derived MET levels for structured activities in a laboratory setting. The thigh placement showed excellent agreement for classifying activity intensity (κ=0.89, 95% CI: 0.86–0.93, p < .001; 90.9% agreement) and type (κ=0.81, 95% CI: 0.76–0.86, p < .001; 90.5% agreement). Sedentary and MVPA activities were classified with excellent accuracy (means = 97.7% and 83.8%, respectively), while light activities showed mixed results (42.6–87.9%). In contrast, the hip and wrist placements showed fair-to-slight agreement (κ≤0.30) and poor accuracy for light activities. These findings support the thigh as the optimal wear location and identify performance reductions for other locations. Further research should validate the SENS in free-living conditions and diverse populations.