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Effects of Exercise Modality on Insulin Resistance and Functional Limitation in Older AdultsA Randomized Controlled Trial
Lance E. Davidson, PhD;
Robert Hudson, MD, PhD;
Katherine Kilpatrick, MD;
Jennifer L. Kuk, PhD;
Kathleen McMillan, MSc;
Peter M. Janiszewski, MSc;
SoJung Lee, PhD;
Miu Lam, PhD;
Robert Ross, PhD
Arch Intern Med. 2009;169(2):122-131.
Background Authorities advocate that resistance and aerobic exercise are essential for reducing risk factors for chronic disease and disability in older adults. However, the incremental effects of combined resistance and aerobic exercise compared with either modality alone on risk factors for disease and disability is generally unknown.
Methods Participants were 136 sedentary, abdominally obese older men and women recruited from September 30, 2002, through November 15, 2006, at Queen's University. Participants were randomized to 1 of the following 4 groups for 6 months: resistance exercise, aerobic exercise, resistance and aerobic exercise (combined exercise), or nonexercise control. Primary outcomes were analyzed by an intent-to-treat model and included changes in insulin resistance by hyperinsulinemic-euglycemic clamp and functional limitation using the average change in 4 tests combined (average z score).
Results After controlling for age, sex, and baseline value, insulin resistance improved compared with controls in the aerobic exercise and the combined exercise groups but not in the resistance exercise group. Improvement (mean [SE]) in the combined exercise group was greater than in the resistance exercise group (9.2 [1.3] vs 1.8 [1.3] mg/mL/µIU per kilogram of skeletal muscle per minute x100 [P < .001]) but not in the aerobic exercise group (9.2 [1.3] vs 6.5 [1.3] mg/mL/µIU per kilogram of skeletal muscle per minute x100 [P = .46]). Functional limitation improved significantly in all groups compared with the control group. Improvement in the combined exercise group was greater than in the aerobic exercise group (0.5 [0.1] vs –0.0 [0.1]; standard units, z score [P = .003]) but not in the resistance exercise group. Improvement in the resistance exercise group was not different from the aerobic exercise group.
Conclusion The combination of resistance and aerobic exercise was the optimal exercise strategy for simultaneous reduction in insulin resistance and functional limitation in previously sedentary, abdominally obese older adults.
Trial Registration clinicaltrials.gov Identifier: NCT00520858
Author Affiliations: School of Kinesiology and Health Studies (Drs Davidson, Hudson, Kilpatrick, Kuk, Lee, and Ross; Ms McMillan; and Mr Janiszewski), Divisions of Endocrinology and Metabolism (Drs Hudson and Ross) and Geriatrics (Dr Kilpatrick), Department of Medicine, and Department of Community Health and Epidemiology (Dr Lam), Queen's University, Kingston, Ontario, Canada; New York Obesity Research Center, St Luke’s-Roosevelt Hospital and the Institute of Human Nutrition, Columbia University, New York, New York (Dr Davidson); School of Kinesiology and Health Science, York University, Toronto, Ontario, Canada (Dr Kuk); Weight Management and Wellness Center, Children's Hospital of Pittsburgh, University of Pittsburgh, Philadelphia (Dr Lee).
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