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Title: CAN DUAL ENERGY X-RAY ABSORPTIOMETRY PROVIDE A VALID ASSESSMENT OF CHANGES IN THIGH MUSCLE MASS WITH STRENGTH TRAINING IN OLDER ADULTS?

Author
item DELMONICO, MATTHEW - UNIV OF MD, COLLEGE PARK
item KOSTEK, MATTHEW - UNIV OF MD, COLLEGE PARK
item JOHNS, JOSHUA - UNIV OF MD, COLLEGE PARK
item HURLEY, BEN - UNIV OF MD, COLLEGE PARK
item Conway, Joan

Submitted to: European Journal of Clinical Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/18/2007
Publication Date: 8/8/2007
Citation: Delmonico, M.J., Kostek, M.C., Johns, J.R., Hurley, B.F., Conway, J.M. 2007. Can dual energy x-ray absorptiometry provide a valid assessment of changes in thigh muscle mass with strength training in older adults? European Journal of Clinical Nutrition. Available: doi:10.1038/sj.ejcn.1602880.

Interpretive Summary: Strategies to reduce the loss of skeletal muscle (SM) mass in older adults include both aerobic and strength training (ST). A longitudinal ST intervention study was conducted in fifty previously sedentary, relatively healthy men between the ages of 50 and 83 years. One part of the study determined how well a relatively non-invasive and less expensive method of determining muscle mass, dual-energy x-ray absorptiometry (DXA), compares to the gold-standard of computed tomography (CT) for measuring changes in total thigh SM mass with ST. After approximately 10 weeks of single-leg ST of the thigh muscles there was a statistically significant increase in thigh SM mass with ST measured by both CT (3.0 plus or minus 0.4 percent) and DXA (3.9 plus or minus 0.6 percent) methods, and there was no significant difference in percent change between the two methods. Additionally, graphic analyses indicate that the percent changes between CT and DXA methods were not significantly different in the trained leg (mean difference = 0.89 percent) or untrained leg (mean difference = 0.13 percent). These results suggest that DXA-estimated changes in thigh skeletal muscle mass with ST are similar to the changes in skeletal muscle mass as measured by multi-slice CT. Since DXA is a readily available technology that is easier, less invasive, and less expensive, it can be used in studies of large populations where cost and availability are important limitations. These data will be of interest to epidemiologists and also health care practitioners who are responsible for monitoring muscle mass changes in older adults.

Technical Abstract: A longitudinal strength training (ST) intervention study was conducted in fifty previously sedentary, relatively healthy men (n = 23, 60 [SD=7.5] yr) and women (n = 27, 60 [SD=9.3] yr). One part of the study determined how dual-energy x-ray absorptiometry (DXA) compares to computed tomography (CT) for measuring changes in total thigh skeletal muscle (SM) mass with ST. After approximately 10 weeks of unilateral (single-leg) ST of the knee extensors there was a significant increase in thigh SM mass with ST measured by both CT (3.0 plus or minus 0.4 percent) and DXA (3.9 plus or minus 0.6 percent) methods (both P less than 0.001), and there was not a significant difference in percent change between the two methods, although there was a substantial absolute difference in SM mass between the two methods at baseline. Additionally, Bland-Altman plots indicate that the percent changes between CT and DXA methods were not significantly different in the trained leg (mean difference = 0.89 percent, 95 percent Confidence Interval = -0.151 to 1.940) or untrained leg (mean difference = 0.13 percent; 95 percent Confidence Interval = -0.817 to 1.069). These results suggest that DXA-estimated changes in thigh skeletal muscle mass with ST are similar to the changes in skeletal muscle mass as measured by multi-slice CT.