Leg Strength Declines with Advancing Age Despite Habitual Endurance Exercise in Active Older Adults.Marcell, Taylor J. Ph.D.; Hawkins, Steven A. Ph.D.; Wiswell, Robert A. Ph.D.Journal of Strength & Conditioning Research: Post Acceptance: September 14, 2013 doi: 10.1097/JSC.0000000000000208 Original Investigation: PDF Only Abstract 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, while 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 ([almost equal to] 4.8 yrs apart) was performed on 59 men (age at start of study: 58.6+/-7.3 yr) and 35 women (56.9+/-8.2 yr) who used endurance running as their primary mode of exercise. There were no changes in fat-free mass while 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 ([almost equal to]5%/yr) and knee flexion ([almost equal to]3.6%/yr) 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 while there were no changes in LBM 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. Copyright (C) 2017 by the National Strength & Conditioning Association.