Date of Award
1-5-2018
Degree Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Kinesiology and Health
First Advisor
J. Andrew Doyle
Second Advisor
Gordon L. Warren
Third Advisor
Christopher P. Ingalls
Fourth Advisor
Jeff S. Otis
Abstract
PURPOSE: The aim of this study was to determine if knee extensor injury induced by 1 h of downhill running attenuated force production in uninjured skeletal muscle (e.g., elbow flexors). METHODS: Recreationally active subjects (n = 12) completed a two group (injury vs control) repeated measures design with the injury group running downhill for 1 h and the control group performing only the measurement procedures. Strength and percent voluntary muscle activation were measured using an isokinetic dynamometer and electrical stimulation of the elbow flexors and knee extensors before and after a fatigue protocol at the following time points in relation to the downhill run: 15 min pre, 15 min post, 24 h post, and 48 h post. Blood samples were collected at the same time points to measure IL-1β and TNF-α concentrations. RESULTS: Knee extensor strength was significantly reduced by 53.5±9.9% immediately post-injury and remained reduced for up to 48 h in the injury group. Elbow flexor strength was significantly reduced immediately and 24 h post-injury by 13.2±3.9% and 17.3±4.0% respectively in the injury group. Elbow flexor electrically stimulated strength was not found to be different at any time point (P = 0.561). Elbow flexor activation was significantly reduced compared to control at 24 and 48 h post-injury by 22.9±9.1% and 13.5±5.7% respectively. No differences were observed in IL-1β or TNF-α between groups. CONCLUSION: A 1 h downhill run significantly injured the knee extensors. The elbow flexor muscles remained uninjured based on electrically stimulated strength, but voluntary strength of these muscles was impaired due to reduced activation. This suggests an injury to the knee extensors can impair strength in uninjured muscles by reducing voluntary activation. The mechanism behind this reduction remains undetermined.
INDEX WORDS: Downhill running, Muscle injury, Central nervous system, Inflammation
DOI
https://doi.org/10.57709/11228933
Recommended Citation
Brandenberger, Kyle, "Downhill running impairs activation and strength of the elbow flexors." Dissertation, Georgia State University, 2018.
doi: https://doi.org/10.57709/11228933
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