PURPOSE: The overall physical demands placed on recruits completing United States Marine Corps (USMC) training is high and comes concomitantly with high rates of injuries. Load carriage with heavy loads is of particular concern. However, load carriage conditioning, if optimised, can reduce injury risk. METHODS: Retrospective injury data of recruits completing training informed this study. Data were drawn from recruits completing an original load carriage (OLC) program (n=2,363) and those completing a modified load carriage (LCMOD) program (n=681). Musculoskeletal injury data were drawn from the USMC San Diego sports medicine injury database. A population estimate of the OLC:LCMOD relative risk ratio (RR) was calculated. RESULTS: The proportion of injuries sustained by the LCMOD cohort (n=268; 39%) was notably lower than that sustained by the OLC cohort (n=1,372; 58%). The reoccurrence rate *f injury for LCMOD soldiers compared to the OLC was 0.68 (95% CI 0.61 to 0.75). The leading nature of injury (i.e., sprains and strains) was consistent between both cohorts (OLC: n=396; 29% vs. LCMOD: n=66; 25%). Inflammation (n=172; 13%) and fractures (n=144; 11%) were next most common for OLC recruits; while pain (n=58; 22%) and medial tibial stress syndrome (n=18; 8%) were next most common for LCMOD recruits. While stress reactions were proportionally higher in LCMOD (n=17; 6%) when compared to OLC (n=4; 0.3%), stress fractures were proportionality lower (LCMOD: n=9; 3% vs. OLC: n=114; 8%). Pre-existing / chronic injuries were higher in LCMOD (+5%) while new overuse injuries were lower (-7%). Totalling 65% (OLC) and 70% (LCMOD) of reported injuries the knee, lower leg, ankle, and foot were the top 4 bodily sites of injuries, although there were variations in the orders of presentations (See Table 1 for top 10 bodily sites). RELEVANCE: Careful periodisation and planning of a load carriage program can reduce injuries without reducing training outcomes
