Honors Theses

Date of Award

Spring 5-9-2020

Document Type

Undergraduate Thesis



First Advisor

Xin Ye

Relational Format



Downhill running exercise has shown damaging effects on the lower body muscles. However, its effects on the remote nonlocal upper limb muscle’s neuromuscular functions are not well studied. Purpose: To examine the potential effects of a 1-hour downhill running exercise on the elbow flexor muscle neuromuscular functions and performance. Methods: Seventeen healthy and physically active young adults (Control: n = 9; Running: n = 8) participated in and completed this study. The Control group rested for 30 minutes while the Running group performed 1-hour of downhill running at a 10% decline on a treadmill. Before (Pre), immediately after (Post), 24 hours (Post24), and 48 hours (Post48) after the Running or Control, dependent variables (knee extensor muscle soreness, passive knee extension range of motion [ROM], elbow flexor isometric strength, elbow flexor voluntary activation [VA], and the surface electromyography [EMG] amplitude of the biceps brachii during a submaximal isometric contraction at 50% of the Pre-testing maximal strength were measured. Separate two-way mixed factorial (time [ΔPost-Pre vs. ΔPost24-Pre vs. ΔPost48-Pre] × group [Control vs. Running]) analyses of variance (ANOVAs) were used to examine the potential changes in the dependent variables. Results: Knee extensor muscle soreness level was significantly greater in the Running than that in the Control group following the downhill running exercise and remained elevated throughout the entire 48 hours after the exercise. This was accompanied by the knee extension isometric strength response (time merged marginal mean ± SE: Running = -6.9 ± 3.5% vs. Control = 1.0 ± 3.2%). There was no two-way time × group interaction, nor the main effect for group for the ROM, elbow flexion isometric strength, and elbow flexor VA. However, there was a main effect for group (p = 0.005) for the elbow flexion resting twitch force (time merged marginal mean ± SE: Running = -19.6 ± 6.3% vs. Control = 8.7 ± 5.9%). Conclusions: The 1-hour downhill running exercise did induce muscle damage on the knee extensor muscles. In addition, the damaging exercise influenced the remote upper limb elbow flexor muscles at a peripheral level lasting a prolonged period.

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Creative Commons Attribution 4.0 International License
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