Is There a Valid App for That? Validity of a Free Pedometer iPhone Application

Background: This study examined the validity of a selected free pedometer application (iPedometer; IP) for the iPhone that could be used to assess physical activity. Methods: Twenty college students (10 men, 10 women; mean age: 21.85 +/- 1.57 yrs) wore an iPhone at 3 locations (pocket, waist, arm) and a Step Watch 3 Step Activity Monitor (SW) on their right ankle while walking on a treadmill at 5 different speeds (54, 67, 80, 94, 107 m.min(-1)). A research assistant counted steps with a tally counter (TC). Results: Statistical significance between the TC, SW, and IP was found during every condition except IF in the pocket at 107 m-min(-1) (F-2,F-38 = .64, P = .54). Correlations involving the IP revealed only 1 positive correlation (IP on arm at 54 m.min(-1)) for any of the conditions (r = .46, P = .05). Conclusion: The IP application was not accurate in counting steps and recorded significantly lower step counts than the SW and TC. Thus, the free pedometer application used is not a valid instrument for monitoring activity during treadmill walking.