Influence of Age and Body Mass Index on Measures of Physical Fitness in U.S. Army Soldiers

Abstract

This study describes associations between age, body mass index (BMI), and performance on three common measures of physical fitness: maximum pushups in 2 min, maximum sit-ups in 2 min, and 3.2-km run for time. Subjects were 5,346 healthy male soldiers, ages 18 to 53 years. Before age 30, there were few age-related differences between the youngest and the older age groups on any test; after age 30, performance declined as age increased, averaging 16%, 17%, and 7% per decade for push-ups, sit-ups, and the run, respectively. Regression analysis showed that age accounted for 10%, 15% and 9% of the variance in push-up, sit-up, and run performances, respectively. When BMI was added to the regression model it increased the variance accounted for in the run to 16% (age plus BMI) but did not explain variance in push-ups or sit-ups. There are systematic age-related declines in the performance of push-ups, sit-ups, and 3.2-km running, with age alone accounting for only 9% to 15% of the total performance variance in this sample of healthy men.