Introduction The physical and mental training load can be high during military service. Therefore, tailored preconditioning programmes based on assessment of physical fitness could increase readiness for military service, especially among those ones with lower baseline fitness level. The purpose of present study was to investigate how self-assessed health behaviour, physical activity and muscle fitness can predict physical fitness in young male and female military cohorts.

Methods Demographics, health behaviour and daily physical activity preceding military service were surveyed by a questionnaire. Thereafter, physical fitness was assessed during the military service by the tests of 12 min running, 1 min push-ups and sit-ups. Explosive power of the lower extremities was studied by maximal standing long jump. Measurements of body anthropometry consisted of body mass, height, and waist circumference.

Results The two strongest individual predictors of objectively measured running distance in 12 min were self-reported physical activity and physical readiness in both men and women. Self-reported physical activity, readiness for military service, sitting time, education, smoking and body anthropometrics together explained 52% of the variance in the 12 min running test result (R²=0.52, mean absolute percentage error (MAPE) 8.8%, mean absolute error (MAE) 207 m) in men, while for women the predictive values were weaker. Addition of muscle fitness results to the adjusted regression model further improved the model, which explained 59% of the variance in the 12 min running tests result of male conscripts (R²=0.59, MAPE 7.8%, MAE 181 m).

Conclusion In the present study, self-reported physical activity, muscle fitness, physical readiness for military service, sitting time, education, smoking and body anthropometrics predicted inadequately the measured endurance capacity among recruits. The present questionnaire-based variables do not accurately predict physical fitness of recruits and thus, they are not either suitable for practical use for preconditioning programmes or preselection before entering the military service.