Abstract
Introduction: Perimenopause is associated with adverse body composition and strength changes, yet resistance training and creatine monohydrate (CM) remain underrepresented in this population. This study examined the effect of six-weeks of high-intensity resistance training (HIRT) with or without CM on body composition, muscle size and quality, strength, volume, and sleep in perimenopause. Methods: Fifty-one perimenopausal women (Age: 46.2±4.6 years; Body Mass Index: 25.4±4.0 kg/m2) were randomized to CM, placebo (PL), or control (CON). CM and PL completed a 5-day loading (CM: 20g/day; non-caloric PL: 14.5g/day), followed by a maintenance phase (CM 4.5g/day; PL gummies) combined with six-weeks of HIRT; CON maintained normal activity. Lean soft-tissue (LST; kg) was assessed from dual-energy x-ray absorptiometry. Muscle characteristics were determined from peripheral quantitative computed-tomography [muscle area (MuA); cm2; muscle density (MuD); mg/cm3]; and ultrasound [muscle cross-sectional area (mCSA): cm2; echo intensity (EI): a.u.]. Sleep was determined from a wrist-worn wearable. Results: CM resulted in increased LST compared to PL (mean difference±standard error: 0.380±0.431 kg, p=0.999) and CON (1.052±0.474 kg, p=0.096). Muscle size increased in CM compared to CON (MuA: 6.11±2.19 cm2; mCSA: 3.222±1.051 cm2; p=0.011-0.023), but not PL. No main treatment effects were observed for MuD or EI. Both lower (CM: 139.6±34.1 lbs; PL: 126.2±31.5 lbs; p< 0.001) and upper body (CM: 9.0±3.4 lbs; p=0.031; PL: 8.1±3.0 lbs; p=0.032) strength increased compared to CON, with no volume differences. No training by treatment interactions were observed for sleep. Conclusion: HIRT improved muscle outcomes, with CM adding 0.38 kg to LST and 148.6 lbs to strength.