Balance abilities in high dynamic-sport athletes with different maximal voluntary contraction

Background: Previous studies have shown that muscle force control during submaximal isometric contractions is associated with the ability of dynamic balance to a greater extent than static balance in healthy adults. However, the effect of maximal voluntary contraction (MVC) on balance abilities of athletes with high dynamicsport, which are most popular in Thailand, needs to be addressed. Objective: To determine static and balance abilities of high dynamic-sport athletes at different levels of MVC. Materials and methods: Three groups of high dynamic-sport athletes at different levels of maximal voluntary contraction (MVC), were voluntarily recruited using a sports matrix classification. Outcome measures comprised the Balance Error Scoring System (BESS) and the Star Excursion Balance Test (SEBT). Correlations between BESS and SEBT and confounding variables comprised of performance time of the Mcgill core endurance tests (Core), single-leg sit-to-stand (STS) test, and flexibility were investigated using Pearson’s correlation. After controlling for Core and STS, a factorial analysis of covariance (ANCOVA) was used to determine group differences in SEBT and BESS variables. Results: Athletes with high- and low- MVC had significantly different reaching distances in all SEBT directions (all, p<0.05). Significant differences between the high- and the moderate- MVC groups were observed in anterior and lateral directions (p<0.05). A significant difference between the moderate- and the low MVC groups was found in the medial direction (p<0.05). After controlling for Core and STS, the observed group differences disappeared, except in the posterolateral reaching distance between the high- and the low-MVC groups (p<0.05). A significant difference between the high- and the low-MVC groups was only observed in the total foam BESS scores with tandem stance (p<0.05) and then disappeared after adjusting for Core and STS (all, p>0.05). Conclusion: The observed differences in all SEBT directions among groups and the difference in the total BESS scores between the high- and the low- MVC, which were observed only in challenged conditions i.e., tandem-foam stance, suggested that dynamic, but not static balance performance of athletes with high dynamicsport appears to be associated with the magnitude of MVC. Core and STS, but not flexibility, are considered significant contributions to their balance performance.