Public health recommendations to get 150 minutes per week of moderate-intensity physical activity could be met by walking 100 steps per minute in that time, but the number of steps needed varies depending on the height of the individual, preliminary data in a small study suggest.
Investigators measured the height, body mass index, and leg length of 20 healthy adults, then measured oxygen uptake by connecting them to a portable spirometer during five 6-minute walks at different speeds. One researcher set the pace in front of the subject using a distance-measuring wheel and cycle computer, and another followed behind to measure steps using a hand-operated counter.
They defined moderate-intensity activity as expending three metabolic equivalents (METs), with each MET defined as oxygen uptake of 3.5 mL/kg per minute. Using the subjects' mean values for body mass index and leg length, they estimated that 100 steps per minute would be needed to expend 3 METs, reported Michael W. Beets, Ph.D., of the University of South Carolina, Columbia, and his associates.
Individuals with longer legs, however, needed fewer the steps for moderate-intensity activity. The correlation between height and leg length suggests that to expend 3 METs, a 5-foot-tall person would need 111 steps per minute, someone who is 5 feet 6 inches tall would need 103 steps per minute, a 6-foot-tall person would need 94 steps per minute, and someone who is 6 feet 6 inches tall would need 85 steps per minute, the investigators said (J. Sci. Med. Sport 2010 [doi:10.1016/j.jsams.2009.11.002]).
The researchers extrapolated that, in order to get 30 minutes of moderate-intensity physical activity, a 5-foot person would need to take 3,330 steps, while a 6-foot person would need only 2,820 steps—a 510-step difference. To meet the public health goal of 150 minutes per week of moderate-intensity activity would require 16,650 steps within that time period for someone 5 feet tall, compared with 14,100 steps for someone 6 feet tall—a difference of 2,550 steps.
The small size of the study limits the ability to generalize the results, but some of the findings are supported by previous data suggesting that 100 steps per minute may be a useful marker on average for meeting moderate-intensity activity goals (Am. J. Prev. Med. 2009;36:410-5).
Disclosures: The investigators stated that they did not have any conflicts of interest.