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Effect of Strength Training on Bone Mineral Content and Density in Premenopausal Women: 2040: Board #191 9:30 AM – 10:30 AM

Warren, Meghan; Petit, Moira A.; Hannan, Peter J.; Schmitz, Kathryn H. FACSM

Medicine & Science in Sports & Exercise: May 2006 - Volume 38 - Issue 5 - p S352
Thursday Morning Poster Presentations: Posters displayed from 7:30 a.m.-12:30 p.m.: One-hour author presentation times are staggered from 8:30-9:30 a.m. and 9:30-10:30 a.m.: C-36 Free Communication/Poster - Sports Medicine, Injury Prevention, Bone Health THURSDAY, JUNE 1, 2006 8:30 AM - 10:30 AM ROOM: Hall B

1University of Minnesota, Minneapolis, MN.

2University of Pennsylvania, Philadelphia, PA.

Email: warren@epi.umn.edu

PURPOSE: To determine the effect of a two-year, twice-weekly strength training program on bone mineral content and density (BMC and BMD) in healthy, premenopausal women.

METHODS: Participants were 148 overweight, premenopausal women aged 25–44 in the Strong, Healthy, and Empowered (SHE) Study. Women who became pregnant or used corticosteroids were excluded from these analyses. All participants were inactive and untrained at baseline. Participants were blocked by age and body fat percent, and were randomized to either a progressive strength-training program (ST, n=72) that stressed all major muscle groups or a standard care control group (C, n=76). Measurement visits were conducted at baseline, year 1, and year 2, and included body composition and anthropometry, muscle strength with bench and leg press one repetition maximum testing, food frequency questionnaire, and physical activity assessment using an accelerometer. Total body, proximal femur, and lumbar spine BMC and BMD were measured by dual energy x-ray absorptiometry (DXA, GE/Lunar Prodigy). Analyses were completed as intent-to-treat, and mixed models with a random intercept and slopes were used to assess the effect of strength training on the bone outcomes.

RESULTS:After adjustment for baseline height and weight, both the ST and C group showed increased BMC at the femoral trochanter (ST 2.2% vs. C 1.3%), total femur (ST1.0%vs. C 0.6%), and lumbar spine (ST 2.1% vs. C 1.0%) BMC. Between group differences for these sites were not significant. In contrast, femoral neck (FN) BMC showed a significant difference in the slopes between strength training and control groups (p= 0.04) with no change in the strength training group and a 1.9% decrease in the control group. BMD did not differ between groups at any site and was relatively stable in all sites over the two years. Muscle strength and fat-free mass increased more in the ST than in the C group (p=0.002 and p=0.03, respectively).

CONCLUSIONS: BMC, but not BMD increased in this cohort of premenopausal women except at the femoral neck region. Strength training increased muscle strength and fat free mass and prevented loss of BMC at the femoral neck. As FN BMD did not change, this suggests strength training influenced bone size. Two years of twice weekly strength training had no effect on lumbar spine or total femur bone outcomes.

© 2006 American College of Sports Medicine