Acute Cross?over Effects of Lower Limb Muscle Fatigue on Movement Strategies of Young Adults During Upright Standing

Abstract

Research Question: Are there acute cross-over effects of lower limb muscle fatigue on movement strategies of young adults during upright standing?

Background and Significance: Our study made use of three major concepts: the cross-education phenomenon, muscle fatigue, and postural control. The crosseducation phenomenon pertained to the effects of training one side of the body to the untrained contralateral or opposite side. Muscle fatigue was the decrease in maximal force as a response to contractile activity. Lastly, postural control was the ability that allowed one to maintain upright standing. Looking at these three components¿the cross-education phenomenon, muscle fatigue, and postural control¿that have been studied over the last century, we developed a research idea that used the influence these three had on each other. Our research generated a quantitative analysis of the cross-educational phenomenon on postural control by observing contralateral muscle fatigue.

Materials and Methods: Twenty individuals (17 males, 3 females) were enrolled in the study. Participants were healthy young adults, with no lower extremity injuries, normal or corrected-tonormal vision, no known balance disorder, and no neuromuscular disorder or impairment. Postural control data was collected with a force plate (OR6-7, AMTI, Advanced Mechanical Technology, Inc., Watertown, MA) that recorded forces and moment data. Participants performed pre- and post-fatigue balance assessments on a force plate, including single-legged standing with variations of the dominant and nondominant leg and stable and unstable surface types. Following the initial balance assessment, a fatigue task of single-leg standing calf raises was performed until exhaustion. Data from the pre-fatigue balance task and post-fatigue balance task were analyzed and compared.

Results: The Coefficient of Variation in the Anterior-Posterior (CVAP) direction for the fatigued Dominant Leg exhibits steep variability, indicating significant sway during the post-fatigue balance task, as expected. The CVAP for the unfatigued Nondominant Leg also shows an increase in variability, though not as steep, which can be attributed to the crossover effect (p=0.043).

Conclusion: Acute fatigability on one of the lower limbs in our subjects influenced contralateral postural stability and control during upright standing. This was supported objectively by measurements of the muscle activity from the force plate device. As for impact, we increased our understanding of postural control training through cross-education and provided additional evidence via objective data. Future work can include increased power, more diverse subjects, or, or other limbs. We hope that our study has provided valuable insights for various applications, such as physical rehabilitation or performance training.