Choice of Activity-Intensity Classification Thresholds Impacts upon Accelerometer-Assessed Physical Activity-Health Relationships in Children

BACKGROUND It is unknown whether using different published thresholds (PTs) for classifying physical activity (PA) impacts upon activity-health relationships. This study explored whether relationships between PA (sedentary [SED], light PA [LPA], moderate PA [MPA], moderate-to-vigorous PA, vigorous PA [VPA]) and health markers differed in children when classified using three different PTs. METHODS 104 children (63 girls) aged 10-14 years wore an RT3 triaxial accelerometer for seven days and measures of adiposity and cardiometabolic risk markers were taken. RESULTS Significant associations (p< .05) in boys were found between LPA and body mass index z-score and waist circumference z-score for the Rowlands et al PT only (β =  .459 and.401, respectively) and body fat% (BF%) for the Chu et al PT only (β = .322) and in girls with BF% for the Rowlands et al PT only (β =  .303) and systolic BP and blood glucose for the Vanhelst et al PT only (β = -.298 and -.283, respectively). MPA was significantly (p<.05) associated with BF%, diastolic BP, and cardiorespiratory fitness (CRF) for the Chu et al PT only in girls (β = -.436, -.529, and .446, respectively). SED was significantly (p<.05) associated with triglycerides (β = .492) for the Rowlands et al PT only in boys and VPA with CRF (p<.05) for the Rowlands et al and Vanhelst et al PTs only in girls (β = .416 and .352, respectively). CONCLUSIONS The choice of PT impacted upon activity-health relationships. A consensus on appropriate accelerometer thresholds for quantifying PA intensity and sedentary behaviour is needed in order to make accurate evidence-based recommendations for health promotion.