LAUSR

INTRODUCTION The menopause transition yields significant physiologic alterations. The purpose was to characterize lean soft tissue (LST), muscle size (muscle cross-sectional area; mCSA), muscle quality (echo intensity; EI), and strength across the menopause transition. A secondary aim was to evaluate whole body protein turnover in a subsample of women. METHODS Seventy-two healthy women were enrolled in this cross-sectional study based on menopause stage (PRE: n = 24; PERI: n = 24; POST: n = 24). Whole-body LST was measured via dual-energy x-ray absorptiometry and muscle characteristics (mCSA and EI) were measured via B-mode ultrasound of the vastus lateralis. Maximal voluntary contractions (MVC; Nm) of the knee extensors were evaluated. Physical activity (min per day) was accounted for using the International Physical Activity Questionnaire. A sub-sample of women (n = 27) ingested 2.0 g of 15N-alanine to determine whole-body net protein balance (NB; g/kg BM/day). RESULTS Significant differences were evident in LST (p = 0.022), leg LST (p = 0.05) and EI (p = 0.018) between menopause stages. Bonferroni post-hoc comparisons revealed greater LST in PRE vs PERI (mean difference [MD] ± SE: 3.8 ± 1.5 kg; p = 0.048) and POST (3.9 ± 1.5 lbs; p = 0.049). Similarly, EI was significantly higher in PERI PRE (MD: 18.3 ± 7.1 a.u.; p = 0.036.). There was no significant difference in mCSA (p = 0.082) or in MVC (p = 0.167). NB was significantly different across groups (p = 0.026); NB was greater in PRE compared to PERI (MD: 0.39 ± 0.17 g/kg; p = 0.090), and from PRE to POST (MD: 0.46 ± 0.17 g/kg; p = 0.042). Physical activity was not significantly different across groups but demonstrated a linear increase from PRE to POST. CONCLUSIONS The current findings suggest that LST, muscle quality, and protein balance may be negatively influenced by the menopause transition.