Effectiveness of Polar Activity Computer on Physical Activity in Daily Life

Introduction Feedback and monitoring physical activity (PA) may have a role decreasing sedentary behavior. The aim of this study was to test the effectiveness of a Polar Activity Computer (FA20, Polar Electro Oy, Kempele, Finland) in increasing PA in daily life over 6 month.

Method 50 volunteer healthy subjects were randomly assigned to an intervention (IG) (13 men, 13 women, 48.9 ± 2.3 y, 25.8 ± 7.5 kg/m²) and control group (CG) (14 men and 11 women, 45.8 ± 2.2 y, 24.9 ± 7.6 kg/m²) after baseline measurements. At baseline, all subjects wore an accelerometer (GT1M, Actigraph, Florida, USA) for 8 days and completed an online questionnaire on health and PA habits. After these measures the groups were randomised and the IG was given a general information on PA and provided with a Polar FA20. FA20 detects activity based on in-built accelerometer and gives the user feedback about active time spent in health and fitness related activity, accumulated steps and energy expenditure. The CG did receive only general information on PA. After one week and after two, four and six months, 8 days activity measures with the GT1M and the survey were repeated in both groups. The averaged GT1M data over the week (counts/min) was taken as mean PA per week. GT1M data was assigned to sedentary when activity was less than 100 counts. The remaining activity data was classified as light, moderate or vigorous according to Swartz et al (1). The data was analysed using Mixed Models to determine time and group effects on mean PA per week and time spent in moderate and vigorous activity (MVPA).

Results The mean daily PA in the IG and CG was 350±138 and 365±109 counts/min at baseline, respectively. Time spent in MVPA was 144±51 and 142±37 min at baseline in the IG and CG, respectively. Mean daily PA and MVPA did not change over 6 months. There were no significant differences in PA between the groups at any measurement period. However, wearing the FA20 during the whole trial increased time spent in moderate activity (p=0.007) and nearly increased overall mean weekly PA (p=0.0591). There was no effect of wearing the FA20 on light or vigorous activity.

Discussion Mean daily PA at baseline was comparable to a population study (376 counts/min) (2) indicating that the participants of the present study are active at an average. Polar FA20 seems not to have a major effect on the general activity behaviour. However, wearing the FA20 regularly could increase moderate PA significantly over time in moderately active adults.

References (1)Swartz, A. M., S. J. Strath, D. R. Bassett, JR., W. L. O’Brien, G. A. King, and B. E. Ainsworth: Estimation of energy expenditure using CSA accelerometers at hip and wrist sites. Med Sci Sports Exerc 32: S450-S456, 2000. (2)Hagströmer M, Oja P, Sjöström M: Physical Activity and Inactivity in an Adult Population Assessed by Accelerometry. Med Sci Sports Exerc 39: 1502-08, 2007.