Leg Strength Declines With Advancing Age Despite Habitual Endurance Exercise in Active Older AdultsMarcell, Taylor J.1,3; Hawkins, Steven A.2,3; Wiswell, Robert A.3Journal of Strength & Conditioning Research: February 2014 - Volume 28 - Issue 2 - p 504–513 doi: 10.1519/JSC.0b013e3182a952cc Original Research Abstract Author Information Abstract: Marcell, TJ, Hawkins, SA, and Wiswell, RA. Leg strength declines with advancing age despite habitual endurance exercise in active older adults. J Strength Cond Res 28(2): 504–513, 2014—Age-associated loss of muscle mass (sarcopenia) and strength (dynapenia) is associated with a loss of independence that contributes to falls, fractures, and nursing home admissions, whereas regular physical activity has been suggested to offset these losses. The purpose of this study was to evaluate the effect of habitual endurance exercise on muscle mass and strength in active older adults. A longitudinal analysis of muscle strength (≈4.8 years apart) was performed on 59 men (age at start of study: 58.6 ± 7.3 years) and 35 women (56.9 ± 8.2 years) who used endurance running as their primary mode of exercise. There were no changes in fat-free mass although body fat increased minimally (1.0–1.5%). Training volume (km·wk−1, d·wk−1) decreased in both the men and women. There was a significant loss of both isometric knee extension (≈5% per year) and knee flexion (≈3.6% per year) strength in both the men and women. However, there was no significant change in either isokinetic concentric or eccentric torque of the knee extensors. Our data demonstrated a significant decline in isometric knee extensor and knee flexor strength although there were no changes in body mass in this group of very active older men and women. Our data support newer exercise guidelines for older Americans suggesting resistance training be an integral component of a fitness program and that running alone was not sufficient to prevent the loss in muscle strength (dynapenia) with aging. 1Department of Kinesiology, California State University Stanislaus, Turlock, California; 2Department of Exercise Science, California Lutheran University, Thousand Oaks, California; and 3Department of Biokinesiology, University of Southern California, Los Angeles, California Address correspondence to Taylor J. Marcell, firstname.lastname@example.org. Copyright © 2014 by the National Strength & Conditioning Association.