Temporal changes in the physical fitness of US Army recruits.

This article defines physical fitness and then reviews the literature on temporal trends in the physical fitness of new US Army recruits. Nineteen papers were found that met the review criteria and had published recruit fitness data from 1975 to 2003. The limited data on recruit muscle strength suggested an increase from 1978 to 1998 (20-year period). Data on push-ups and sit-ups suggested no change in muscular endurance between 1984 and 2003 (19-year period). Limited data suggested that maximal oxygen uptake (VO2max) [mL/kg/min] of male recruits did not change from 1975 to 1998 (23-year period), while there was some indication of a small increase in female recruit VO2max in the same period. On the other hand, slower times on 1-mile (1.6km) and 2-mile (3.2km) runs indicate declines in aerobic performance from 1987 to 2003 (16-year period). The apparent discrepancy between the VO2max and endurance running data may indicate that recruits are not as proficient at applying their aerobic capability to performance tasks, such as timed runs, possibly because of factors such as increased bodyweight, reduced experience with running, lower motivation and/or environmental factors. Recruit height, weight and body mass index have progressively increased between 1978 and 2003 (25-year period). Both the body fat and fat-free mass of male recruits increased from 1978 to 1998 (20-year period); however, body composition data on female recruits did not show a consistent trend. In this same time period, the literature contained little data on youth physical activity but there was some suggestion that caloric consumption increased. This article indicates that temporal trends in recruit fitness differ depending on the fitness component measured. The very limited comparable data on civilian populations showed trends similar to the recruit data.