Hormonal contraceptive use and physical performance, body composition, and musculoskeletal injuries during military training

Purpose: To investigate associations between hormonal contraceptive use and physical performance, body composition, and musculoskeletal injuries in basic military training. Methods: 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. Results: 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). Conclusions: Hormonal contraceptive use was not associated with performance or injury outcomes in military training.