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 StepWatch 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 IP in the pocket at 107 m·min(-1) (F(2,38) = .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.