Hormonal Contraceptive Use and Physical Performance, Body Composition, and Musculoskeletal Injuries during Military Training.

Abstract

To investigate associations between hormonal contraceptive use and physical performance, body composition, and musculoskeletal injuries in basic military training. Female British Army recruits ( n = 450) were grouped as nonusers ( n = 182), combined oral contraceptive users (COCP; n = 184), or progestin-only users (POC; n = 144). Physical performance (2.4-km run, lift strength, leg power), body composition, iron and vitamin D status, and bone metabolism were measured at the start (week 1) and end (week 13) of training. Lower body musculoskeletal injuries were recorded from medical records. Training decreased 2.4-km run time (-3.7%) and fat mass (-9.6%), and increased lift strength (4.5%), leg power (1.5%), lean mass (5.4%), and whole-body (0.9%), arms (1.8%), and legs (1.4%) areal bone mineral density ( P ≤ 0.015); the training response was not different between groups ( P ≥ 0.173). Lift strength was lower in COCP users than nonusers ( P = 0.044). Whole-body, trunk, and leg areal bone mineral densities were lower in POC users than nonusers and/or COCP users ( P ≤ 0.041). There were no associations between hormonal contraceptive use and musculoskeletal or bone stress injury ( P ≥ 0.429). Training did not change ferritin ( P = 0.968), but decreased hemoglobin and total 25-hydroxyvitamin-D, and increased parathyroid hormone, c-telopeptide cross-links of type 1 collagen (βCTX), and procollagen type 1 N-terminal propeptide (PINP; P ≤ 0.005); the training response was not different between groups ( P ≥ 0.368). Total 25-hydroxyvitamin-D was higher, and βCTX and PINP were lower, in COCP users than nonusers and POC users; parathyroid hormone was lower in COCP users than nonusers; and βCTX and PINP were higher in POC users than nonusers ( P ≤ 0.017). Hormonal contraceptive use was not associated with performance or injury outcomes in military training.