Incidence of Injury and Physical Performance Adaptations During Military Training

Objective: Strenuous physical activity, such as military training, is known to demand a high degree of physical perfor-mance and to cause overuse injuries. However, the exact rela-tion between injury incidence and physical fitness level and the influence of military training on measures of functional perfor-mance, such as intermittent endurance capacity and maximal jump performance, are not fully described. Methods: A total of 330 military conscripts were prospec-tively followed during military basic training. They were di-vided into 4 self-assessed physical fitness level groups (well trained, trained, less trained, and untrained) and underwent physical performance tests together with registration of injury incidence. Results: Twelve weeks of military basic training was found to result in an overall injury rate of 28%, with an inverse relation between physical fitness level and incidence of overuse injury (P < 0.0001). Furthermore a fourfold higher injury rate was observed in the previously untrained soldiers compared with the well-trained soldiers. An increase in intermittent en-durance capacity (20-m intermittent shuttle run test) was seen in all groups, (13 to 62%, P < 0.05), whereas only the previ-ously untrained group of soldiers improved in aerobic capacity (8 and 16%, P < 0.05; maximal oxygen uptake and Coopers 12-minute running test). Maximal jump performance, both with and without backpack loading (15 kg), decreased (5 to 13%, P < 0.05) in 93 % of the soldiers despite weight loss. Conclusions: Military basic training has a positive effect on intermittent endurance capacity but a detrimental effect on jump performance. Furthermore, low levels of physical fitness are strongly associated with proneness toward overuse injury development in soldiers going through intense training. Key Words: functional muscle strength—intermittent en-durance capacity—overuse injury—training statu