Term of Award

Summer 2023

Degree Name

Master of Science in Kinesiology (M.S.)

Document Type and Release Option

Thesis (open access)

Copyright Statement / License for Reuse

Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.

Department

Department of Health Sciences and Kinesiology

Committee Chair

Nicholas Siekirk

Committee Member 1

Li Li

Committee Member 2

Andrew Flatt

Abstract

Hamstring injuries are common muscle-skeletal injuries with a high recurrence rate. While unmodifiable risk factors (e.g., previous injury) vary, recent evidence has questioned the utility of eccentric exercise in preventing hamstring strains. Furthermore, whether eccentric exercise can transfer to sprinting’s kinetic and kinematic requirements is of question. Therefore, this investigation examines exercise tempo (fast vs. slow eccentric phase), movement strategy (bilateral vs. unilateral), and external load characteristics (coupled vs. independent) bias concentric (CON) and eccentric (ECC) biceps femoris (BF) mean electromyography (mEMG). METHODS: Twenty college-aged students aged 18 – 33 (M = 23.4, SD = 3.12 years) with >3 months of targeted hamstring training >1x per week were recruited and completed two separate lab visits. Lab visits 1 (familiarization) and 2 (experimental protocol) were scheduled for approximately the same time of day, at least 72 hours apart. RESULTS: A main effect of side was detected for BF mEMG during ECC (F (1, 206) = 145.27, p < 0.001) and CON (F (1, 206) = 124.29, p < 0.001). A main effect of tempo was detected for BF (F (1, 206) = 4.144, p = 0.043). The fast tempo (M = 8.20 %MVC, 95% CI: 6.79 to 9.62 %MVC) elicited a higher mEMG when compared to the slow tempo (M = 7.24 %MVC, 95% CI: 5.83 to 8.65 %MVC). Post hoc comparison indicated that the mEMG showed significant differences between tempos (∆M = 0.963 %MVC), p = 0.043. A main effect of side was detected for Gmax ECC (F = (1, 209) 23.28, p < 0.001) and CON (F = (1, 209) 7.85, p = 0.006). CONCLUSION: The prone hamstring exercise resulted in biased recruitment of the contralateral Gmax and BF despite no differences in functional strength ratios (ECC HS [degrees per sec]/ CON Q [degrees per second]). Further investigation is warranted to decipher why this bias exists and whether this phenomenon is a training adaptation or a predictive mechanism for hamstring strain.

Research Data and Supplementary Material

Yes

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