Milk-based proteins are a common choice of post-exercise nutrition to enhance exercise recovery and adaptation. Peri-exercise milk protein ingestion may attenuate exercise-induced muscle damage (EIMD), which is a particular risk to untrained individuals. However, most research has been conducted with males, and due to potential sex differences in EIMD, research with both sexes is required. This parallel-group randomized controlled trial examined the impact of milk protein ingestion on recovery from EIMD. Untrained males and females performed a single bout of leg-based resistance exercise and consumed a milk protein (MILK-PRO: n = 4 males, n = 8 females) or isoenergetic control (CON: n = 4 males, n = 8 females) supplement over 4 days post-exercise (17 doses total). Maximum strength was assessed ≥3 wk pre- and 72 and 168 h post-exercise, and measures of leg circumference, range of motion, muscle soreness, pressure-pain threshold (PPT), and serum creatine kinase concentration ([CK]) were conducted pre-, immediately post-, and 24, 48, 72, and 168 h post-exercise. Resistance exercise induced mild muscle damage that was not attenuated with MILK-PRO relative to CON. Peak increases in [CK] and reductions in PPT were greater in males compared with females. Changes in other markers were comparable between sexes. We conclude that moderate resistance exercise in naïve individuals induces muscle damage without compromising muscle strength. We support sex differences in EIMD and emphasize the need for further research with both sexes. Milk protein ingestion was not beneficial for recovery from EIMD, thus alternative management strategies should be investigated. This trial was prospectively registered at ClinicalTrials.gov PRS (protocol ID: 290580A).
Keywords: exercise; exercise recovery; milk protein; muscle damage; protein supplementation; resistance exercise; sex differences.