# Incidence and Risk Factors for the Development of Stress Fractures in Military Recruits and Qualified Personnel: A Systematic Review

## TL;DR

Stress fractures are common in military personnel, especially recruits, with risk factors including high physical workload, low fitness, and poor nutrition.

## Contribution

This systematic review synthesizes high-quality evidence on stress fracture incidence and risk factors in military populations.

## Key findings

- Stress fracture incidence is much higher in recruits (13.7–1713 per 1000 person-years) than in qualified personnel (2.7–56.9 per 1000 person-years).
- Common fracture sites include the tibia, fibula, and metatarsals, with older and female personnel at higher risk.
- Risk factors for recruits include alcohol consumption, low BMI, lack of prior exercise, and low vitamin D levels.

## Abstract

Stress fractures are a major force preservation risk in military organisations. Although incidence rates and risk factors have been widely examined, a synthesis of high-quality evidence has been lacking. This review aimed to synthesise findings from studies examining stress fracture incidence and risk factors in military populations. The protocol was registered on the Open Science Framework and reported in accordance with PRISMA guidelines. Three databases were searched, and data on incidence, risk factors, and risk ratios were extracted. Study quality was assessed using Joanna Briggs Institute appraisal tools. Seventy studies were included. The incidence of stress fractures in military recruit/trainee populations was substantially higher than among qualified personnel (13.7–1713 vs. 2.7–56.9 per 1000 person-years). Fractures occurred most often in the tibia, fibula, and metatarsals. Higher-risk sub-populations included older and female personnel. Recruits/trainees faced additional risks, such as the following: consuming >10 alcoholic drinks per week; underweight BMI; beginning training without prior exercise of ≥3 sessions/week or ≥7 h/week in the previous year; low serum 25(OH)D levels; prior use of non-steroidal anti-inflammatory drugs; and the initial training stages with the greatest physical loading. Military personnel, particularly recruits, experience high stress fracture incidence, with physical workload and other risk factors contributing to elevated risk.