2019 Volume 8 Issue 1 Pages 9-18
Objectives: This meta-analysis included two separate aims, 1) to perform a comprehensive search of the literature examining heterologous non-local muscle fatigue (i.e., decrement in force-production capacity of a heterologous unexercised muscle) and, 2) to determine the overall effects of non-local muscle fatigue on important parameters such as maximal voluntary force and spinal and supraspinal excitability. Design and Methods: Exploration of all published literature investigating non-local heterologous muscle fatigue was per formed. Primary requirements for data analysis were the inclusion of maximal voluntary force and spinal and supraspinal excitability measures. Using a random effects model, Hedge’s g effect sizes and 95% confidence intervals (CI) were computed. Results: A total of thirty-five effect sizes were computed from six studies. For all outcomes, a negative effect size indicates a decrement in the performance of the unexercised (heterologous) non-local muscle as a result of the fatiguing intervention. For the maximal voluntary force and spinal and supraspinal excitability outcomes, a trivial mean ES = -0.142 (95% CI = -0.164; -0.120, p < 0.001), and ES = -0.072 (95% CI = -0.096; -0.048, p < 0.001) were observed, respectively. Conclusions: Heterologous non-local muscle fatigue was evident, indicating that fatiguing exercises on one muscle group can induce minor decrements (from pre-fatigue baseline) in the maximal voluntary force and spinal and supraspinal excitability outcomes of the heterologous muscle group(s). This analysis provides important quantitative insight regarding the functional consequences of non-local muscle fatigue (i.e., reduced force output and efferent neural drive).