Evaluation of the SenseWear Activity Monitor During Exercise in Cystic Fibrosis and in Health

Objective: Determine the SenseWear Pro3 Armband (SWA) accuracy for estimating energy expenditure (EE) and step count during treadmill walking in cystic fibrosis (CF) compared to healthy adults.

Hypothesis: SWA estimation of EE would be less accurate for CF, than for healthy subjects, due to interference with the SWA skin sensors caused by the high salt concentration in the sweat of CF subjects.

Methods: 17 CF (mean age 26 yr; FEV1 54% predicted) and 17 age-matched control subjects walked slightly faster than their comfortable pace on a treadmill for 20 min, whilst simultaneously wearing the SWA and breathing through an open-circuit indirect calorimetry (IC) system. Subjects' steps were manually counted.

Results: Combined EE data from all subjects showed no significant difference in EE measured by IC (6.0+/-3.4 kcal min(-1)) compared to the SWA estimate (6.3+/-2.5 kcal min(-1)), however the SWA significantly overestimated EE at low exercise intensities and underestimated EE at high exercise intensities. Correlations between EE values, estimated by the SWA and measured by IC, were greater than 0.85 (p<0.001) for both the CF and control group. Standard multiple regression showed that diagnosis of CF independently predicted less than 0.1% of the difference between the IC measure of EE and the SWA estimate. The SWA recorded slightly but significantly fewer steps (113+/-12 steps min(-1)) than the manual count (119+/-9 steps min(-1)).

Conclusion: Diagnosis of CF had no significant negative impact on the accuracy of the SWA estimate of EE. The SWA provided a reasonably accurate estimate of EE and step count during treadmill walking.