Effects of Body Armor and Load Carriage on Lower Limb Joint Movement
STUDY DESIGN Prospective cohort study. OBJECTIVE To describe low back pain (LBP) sustained by soldiers deployed to Afghanistan and identify demographic, fitness, and occupational risk factors of LBP. SUMMARY OF BACKGROUND DATA LBP is the most common injury in deployed soldiers. It results in lost duty days, medical evacuations, and permanent disability. Risk factors for LBP have not been investigated in this population. METHODS This study investigated a US Army Brigade Combat Team deployed to Afghanistan for 1 year. Demographic, fitness, and occupational variables were recorded before and after deployment. Episodes of LBP were assessed using self-report data. Logistic regression was used to investigate predictors of (1) moderate or worse LBP developed during deployment and (2) all LBP developed during deployment. RESULTS The incidence of moderate or worse LBP was 22% in the 805 soldiers studied. Soldiers with elevated risk of LBP were male, in Cavalry or Infantry units, wore body armor for more than 6 hr/d, worked at a desk for 1 to 4 hours a day, spent 5 to 8 hr/d lifting, spent more than 1 hr/wk on walking patrol, spent 21 to 40 hr/wk in a tactical vehicle, or wore equipment. The most parsimonious set of significant predictors for moderate or worse LBP included age, OR = 1.04 (1.01-1.08); fitness score, OR = 0.99 (0.989-0.999); the amount of time spent wearing body armor, OR = 1.16 (1.10-1.23); the amount of time spent on walking patrol, OR = 1.01 (1.003-1.02); and weight of the equipment worn, OR = 1.01 (1.002-1.013). The incidence of all LBP (minor or worse) was 77%. The most parsimonious set of significant predictors for all LBP included age, OR = 1.06 (1.02-1.09); fitness score, OR = 0.99 (0.985-0.997); history of LBP, OR = 2.94, (1.87-4.62); equipment weight, OR = 1.008 (1.003-1.01); and time spent wearing body armor, OR = 1.13 (1.07-1.19). CONCLUSION This study found that being older, having lower fitness scores, wearing armor longer, and wearing heavier loads increased the risk of LBP in deployed soldiers. Units more likely to wear loads such as the Infantry and Cavalry and tasks commonly involving wearing loads such as patrolling all increased the risk of LBP as well.