Adjusting step count recommendations for anthropometric variations in leg length.

Recent public health recommendations for step frequency over a given timeframe (steps min(-1)) associated with moderate-intensity physical activity (MPA) have been developed. The recommendation suggests 100 steps min(-1). This estimate overlooks the impact of anthropometric differences between individuals, notably leg length, which is related to step frequency. Therefore this study examined the impact of leg length on steps min(-1) associated with MPA. Twenty adults age 20-40 years (age 26.4+/-4.6 years, 9 males) walked over-ground at five walking speeds (0.5m s(-1), 0.75m s(-1), 1.0m s(-1), 1.25m s(-1), and 1.5m s(-1)), lasting 6 min each, while wearing a portable gas analyser. Participants' step frequency (steps min(-1)) for each walking speed was determined using a hand-tally counter. Random effects models were used to predict steps min(-1) from METs and participant anthropometric measures (body mass index and leg length [cm]). Model estimates were used to predict steps min(-1) corresponding to heights ranging from 5ft. to 6ft. 6in. (6 in increments). Overall, 100 steps min(-1) corresponded to expending 3 METs (SEE 3.49 steps min(-1), R(2)=0.68). As leg length increased estimated steps min(-1) decreased by -1.15 steps min(-1) (95CI -2.19 to -0.10 steps min(-1)). Based on leg length for individuals 5ft to 6ft 6in., steps min(-1) ranged from 111 to 85, respectively. Established steps min(-1) cutpoints associated with MPA are general public health guidelines and anthropometric differences in leg length should be accounted for when developing step frequency recommendations for physical activity or weight loss studies that include individuals of varying height.