What Are the Acute and Chronic Effects of Initial Military Training on Physiological and Neuromuscular Performance in Military Populations? A Narrative Review

Initial military training (IMT) is designed to physically and mentally transition recruits from civilian to military personnel, typically lasting 6-14 weeks. Accordingly, the content and focus of IMT appear variable, and it is important to understand what effects this training has on recruits. This study reviewed existing literature regarding the acute and chronic effects of IMT on physiological and neuromuscular performance. Using a systematic style search strategy (Google Scholar, EBSCO, PubMed, Medline), 28 relevant studies were identified, focusing on longitudinal (n = 26) and acute (n = 6) effects. The included studies were performed in various branches of the military, but primarily the army, across nations. They rarely disclosed the nature of activities involved, but tended to follow a progressive structure, culminating in scenario-based training specific to their respective branch, to emphasise skills learned earlier in the course. Findings indicate that training causes an acute decrease in strength and power, along with increased cardiovascular strain and maximal oxygen consumption, with these effects being more pronounced in females. Longitudinally, recruits demonstrated improvements in cardiorespiratory endurance, full-body strength and upper-body muscular endurance; however, performance gains typically plateaued by the eighth week. This plateau, most evident in recruits with higher baseline fitness, suggests potential fatigue accumulation from sleep restriction and high physical activity, or a late-stage shift in training focus that provides insufficient stimulus. These results underscore a critical need for standardised assessment protocols to address literature heterogeneity and enhance the comparability of training outcomes across military populations.