Estimating MET values using the ratio of HR for persons with paraplegia

The current compendium of physical activity (CPA) cannot be applied to persons with disabilities due to the lack of physical activity (PA) they are regularly engaged in and inaccurate MET values when applied to persons with disabilities.

The purposes of this study were (a) to determine whether HR ratio during PA and resting can be used to accurately predict MET values of PA in persons with paraplegia, (b) to compare individual calibration (IC) with group calibration (GC) in error reduction, and (c) to examine prediction generalizability through a cross-validation design.

Twenty-seven participants (aged 18-45 yr) with complete and incomplete paraplegia at T6 to L4 participated in this study. Oxygen uptake (VO2) and HR were measured simultaneously at rest and during 10 PA using indirect calorimetry and a Polar HR monitor. Predicted METs were calculated using the HR ratio for six activities by applying regression analysis by group (GC) and individuals (IC), respectively. The derived equations were then cross-validated using the four other activities, and corresponding METs were calculated. Absolute error rates (AC), paired t-test, and correlation (r) were used to determine the absolute and relative difference between observed and predicted METs.

The overall correlation coefficient (r) between HR ratio and observed METs was 0.77 using group regression and 0.93 +/- 0.05 using individual regression. GC (R2 = 0.59, AC = 0.07%-65.25%) was less accurate than IC (R2 = 0.90 +/- 0.10, AC = 1.64%-10.26%). Cross-validation results also showed higher correlations for IC (r = 0.90 in IC and 0.72 in GC) between observed and predicted METs.

HR ratio was able to accurately predict METs of persons with paraplegia. IC estimated METs more accurately than GC.