Temporal changes in physical fitness in Norwegian male and female military conscripts between 2006 and 2020

Reduced physical fitness has been documented in Western children and adults over the past five decades. The same trend has been observed among soldiers, but the number of studies is scarce. Thus, the aim of the present study was to investigate temporal changes in physical fitness in Norwegian conscripts. All conscripts who performed entry fitness tests between 2006 and 2020 were included in the study (n = 105 100; 17% females). Endurance was measured with the 3000 m run, while push-ups, sit-ups, and pull-ups (2006-2016) and medicine ball throw, standing long jump, and pull-ups (2017-2020) were used to measure muscle strength. Mean (95% confidence intervals) 3000 m run time was reduced by 52 (47, 57) seconds in men, 90 (76, 105) seconds in women, and 16 (11, 20) seconds in both sexes combined. Muscle strength increased statistically significantly in four out of five tests in men, three out of six tests in women, and two out of five tests for both sexes combined. Effect sizes for statistically significant changes ranged from 0.06 to 0.82. In conclusion, Norwegian conscripts improved their cardiorespiratory endurance between 2006 and 2020, with improvements observed for most muscle strength tests. When analyzing both sexes combined, the improvements diminished. The latter is attributed to a sevenfold increase in relative number of female conscripts over the 15-year period. The present findings should not be generalized to all young Norwegian men and women since conscripts are selected based on fitness, and only ~15% of the population end up serving.