Original Research: PDF OnlyDownhill Running Impairs Activation and Strength of the Elbow FlexorsBrandenberger, Kyle J.1,3; Warren, Gordon L.2; Ingalls, Christopher P.1; Otis, Jeff S.1; Doyle, J. Andrew1Author Information 1Kinesiology and Health, Georgia State University, Atlanta, Georgia; 2Physical Therapy, Georgia State University, Atlanta, Georgia; and 3Department of Respiratory Therapy, Georgia State University, Atlanta, Georgia Address correspondence to Kyle J. Brandenberger, Kbrandenberger1@gsu.edu. Journal of Strength and Conditioning Research: March 15, 2019 - Volume Publish Ahead of Print - Issue - doi: 10.1519/JSC.0000000000003111 Buy PAP Metrics Abstract Brandenberger, KJ, Warren, GL, Ingalls, CP, Otis, JS, and Doyle, JA. Downhill running impairs activation and strength of the elbow flexors. J Strength Cond Res XX(X): 000–000, 2019—The purpose of this study was to determine if knee extensor injury induced by 1 hour of downhill running attenuated force production in the elbow flexors. Subjects completed either downhill running for 1 hour (injured group; n = 6) or sedentary behavior (control group; n = 6). Strength and voluntary activation (%VA) were measured by isometric twitch interpolation of the elbow flexor and knee extensor muscles at the following time points in relation to the injury: before injury (Pre), after injury (Post), 24 hours after injury (24Post), and 48 hours after injury (48Post). Mean (±SE) knee extensor strength was significantly reduced (53.5 ± 9.9%) Post and remained reduced at 24Post and 48Post in the injury group. Knee extensor muscle twitch strength was reduced Post and 24Post after the downhill run (p < 0.022). Elbow flexor muscle strength was significantly reduced Post (13.2 ± 3.9%) and 24Post (17.3 ± 4.0%). Elbow flexor muscle twitch strength was not significantly different at any time point. Elbow flexor muscle %VA was not significantly reduced compared with Pre, at Post (16.2 ± 5.1%), 24Post (20.9 ± 6.7%), or 48Post (12.9 ± 4.5%). A 1-hour downhill run significantly injured the knee extensors. The elbow flexor muscles remained uninjured, but strength of these muscles was impaired by reduced %VA. These data suggest muscle injury can lead to prolonged strength deficits in muscles distant from the injury and should be accounted for when scheduling training that may lead to delayed-onset muscle soreness. Copyright © 2020 by the National Strength & Conditioning Association.