Objectives: The purpose of this study was to examine the relationship between estrogen use and muscle strength, bone mineral density (BMD), and body composition variables in postmenopausal women. Forty healthy, untrained women participated in this study. Subjects (53-65 years) were > or =5 years postmenopausal and were categorized into either estrogen replacement therapy (ERT n=20) or non-estrogen replacement therapy (Non-ERT n=20) groups.
Methods: Muscular strength was measured by 1-RM testing using Cybex isotonic weight machines. Handgrip strength was measured using a handgrip dynamometer. Diagnostic Ultrasound was used to determine cross-sectional areas of the biceps brachii and rectus femoris muscle groups. BMD of the lumbar spine, proximal femur, and total body was assessed by Dual Energy X-Ray Absorptiometry (Lunar DPX-IQ). Body composition variables were obtained from the total body scan. Serum osteocalcin was measured as an indicator of bone remodeling.
Results: There were no significant differences (P>0.05) for isotonic muscular strength, muscle cross-sectional areas, handgrip strength, or percent fat between ERT and Non-ERT groups. ERT had significantly higher (P<0.05) BMD for the total body, femoral neck and Ward's Area. There were moderate positive relationships between lean body mass and the hip sites (r=0.61-0.70, P<0.05). Regression analyses determined that lean body mass was the strongest predictor of the hip BMD sites. Estrogen use also was a significant predictor for the femoral neck and Ward's Area sites.
Conclusion: Women taking estrogen exhibited similar muscular strength, muscle size, and body composition as their estrogen-deficient counterparts. Estrogen use was also associated with higher BMD for the total body and hip sites. Generally, body composition, specifically lean body mass, influenced hip BMD more than muscular strength or estrogen use.