Night Jumps with Equipment and Self-Reported Musculoskeletal Problems in Military Parachutists: A Cross-Sectional Study.

Background and Objectives: Military parachuting combines landing impact, carried load, and restricted visual information. This study examined the concurrent associations of two primary task exposures-recent jump volume and participation in at least one night jump with equipment-with self-reported parachuting-related musculoskeletal problems; individual characteristics were treated as adjustment variables or exploratory factors. Methods: A cross-sectional study was conducted in 105 parachutists from the Sapper Battalion of the Spanish Parachute Brigade. Exposure and outcome were both recalled for the same preceding 12 months, and their temporal sequence was not recorded. Prevalence was estimated with Wilson 95% confidence intervals, and the two primary exposures were entered simultaneously in Firth bias-reduced logistic regression adjusted for age and body mass index. A modified Poisson model with robust standard errors estimated adjusted prevalence ratios as a sensitivity analysis. Results: Forty-eight participants (45.7%) reported at least one parachuting-related musculoskeletal problem during the preceding year, most frequently at the knee, low back, and upper back or neck. Problems were reported by 79.4% of participants who had performed night jumps with equipment and by 29.6% of those who had not. Night jumps with equipment were associated with the outcome (odds ratio 7.13, 95% confidence interval 2.71-20.66), whereas recent jump volume was not. The adjusted prevalence ratio for the combined exposure was 2.44 (95% confidence interval 1.63-3.64). Conclusions: Night jumps with equipment showed a concurrent association with self-reported musculoskeletal problems, but the design cannot establish whether the exposure preceded the problem or separate the contributions of darkness and equipment. The findings should be treated as hypothesis-generating for prospective, jump-level surveillance.