The Comparison of Ground Reaction Force Between Dominant and Non-Dominant Legs During Ten-sao in Khon Masked Dancers.

Introduction: Leg asymmetry is common in many sports, including dance. Ten-sao, a fundamental practice movement in Khon masked dance, involves symmetrical continuous movements where dancers perform strong stomping actions.

Objectives: to compare ground reaction forces (GRFs) and calculate the absolute symmetry index (ASI) between dominant and non-dominant legs during Ten-sao in Khon masked dancers.

Methods: Fifteen healthy male Khon masked dancers with at least 5 years of experience participated in the study. Each dancer performed Ten-sao continuously for 10 cycles. The GRFs of each leg were assessed using two force plates, capturing in the vertical, antero-posterior, and medio-lateral directions during different phases of the Ten-sao dance. The ASI was calculated to assess symmetry in GRF distribution.

Results: A significant difference in vertical GRF was found during the single-leg stance phase, with the dominant leg exhibiting greater force than the non-dominant leg (P = .023). The median and interquartile range (IQR) for the dominant leg was 90.005 N/kg (IQR 9.73), while the non-dominant leg exhibited a median of 57.494 N/kg (IQR 8.401). These findings highlight the asymmetry in force production between the dominant and non-dominant legs. The ASI showed asymmetries in the antero-posterior direction during double-leg support (DLS), and in the antero-posterior and medio-lateral directions during peak GRF (pGRF). Further asymmetries were observed in the antero-posterior, medio-lateral, and vertical directions during single-leg standing (SLS).

Conclusion: The study reveals significant leg asymmetry in vertical GRF between the two legs among Khon dancers performing Ten-sao. The dominant leg demonstrates higher vertical force during SLS, and various asymmetries are presented in both DLS and SLS phases. Addressing these asymmetries in training programs is crucial for enhancing performance and reducing injury risk for Khon masked dancers.