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Normalizing strength for body size differences in older adults


Medicine & Science in Sports & Exercise: May 1997 - Volume 29 - Issue 5 - p 713-717
Special Communications: Methods

The purpose of this study was to compare the normalization methods of ratio standards, allometry, and ANCOVA with knee extensor strength of older adults. The apparently healthy older volunteers were 71 men (mean ± SD: age, 71± 4 yr; body mass, 81 ± 10 kg; height, 174 ± 7 cm) and 77 women (71 ± 4 yr, 65 ± 8 kg, 160 ± 5 cm, respectively). Strength was defined as peak torque (N·m-1) and measured with a Cybex II isokinetic dynamometer. Body composition was estimated with dual energy x-ray absorptiometry. With allometry, the body mass exponent (0.74) was not statistically different from theory (0.67). Body mass adjusted strengths were 34.7% (allometry), 32.0% (ANCOVA), and 29.4% (ratio standards) greater in older men than women. Allometry revealed that the bone-free lean tissue mass exponent was not different from ratio standard exponent of 1.0. After adjustments by bone-free lean tissue mass, strength in men remained 16.0%(allometry and ratio standards) higher than in women, but strength differences between genders were eliminated with ANCOVA. The methods used to normalize strength yielded similar results with body mass but conflicting results with bone-free lean tissue mass.

Department of Medicine, Osteoporosis Center & Exercise Research Laboratory, University of Connecticut Health Center, Farmington, CT

Submitted for publication March 1996.

Accepted for publication October 1996.

The authors would like to express their gratitude to the research volunteers for their participation and to Bradley Biskup, David Immke, Sally Warner, and Augustus Mazzocca for their technical support.

This work was funded by a grant from USPHS 1U01-AG10382.

Address for correspondence: Michael J. Davies, Diabetes Institutes, Eastern Virginia Medical School, 855 West Brambleton Avenue, Norfolk, VA 23510.

©1997The American College of Sports Medicine