The effect of ankle flexibility on the relationship between knee isokinetic strength and the speed of underwater dolphin kicks in male competitive swimmers

Article type: Research Article

Authors: Shen, Yupeng^{a; b} | Fu, Yanqing^a | Ge, Yu^a | Wen, Yuhong^{c; *}

Affiliations: [a] The School of Physical Education and Sports Science, South China Normal University, Guangzhou, Guangdong, China | [b] The College of Swimming, Beijing Sports University, Beijing, China | [c] The College of Recreation Sport and Tourism, Beijing Sports University, Beijing, China

Correspondence: [*] Corresponding author: Yuhong Wen, The College of Recreation Sport and Tourism, Beijing Sports University, Beijing, China. E-mail: wyhswim@126.com.

Abstract: BACKGROUND: Lower-extremity muscle strength and ankle flexibility play key roles in underwater swimming movements. OBJECTIVES: To investigate the relationship between knee isokinetic strength and the speed of underwater dolphin kicks (UDK-S) in competitive male swimmers and identify whether ankle flexibility affects the association between knee isokinetic strength and UDK-S. METHODS: Fifty-two highly trained male swimmers participated in this study. The speed at which the participants travelled 15 m performing UDKs was calculated as UDK-S. Knee flexor and extensor concentric isokinetic strength at fast (240∘/s) and slow (60∘/s) velocities and ankle flexibility were evaluated. Bayesian framework analysis was conducted to examine the relationship between these variables and determine whether this relationship is influenced by ankle flexibility. RESULTS: There was strong-to-extremely strong evidence (Bayes factor = 24.4 to 198.3) that knee extensor (60∘/s) and knee flexor (60∘/s and 240∘/s) strength are positively and generally moderately correlated with UDK-S. Ankle plantar flexion flexibility was identified to be a moderator between knee extensor strength (60∘/s) and UDK-S. CONCLUSIONS: Knee extensor and knee flexor strength were significantly correlated with UDK-S, and the relationship between knee muscle strength and UDK-S was influenced by ankle plantar flexion flexibility in male competitive swimmers.

Keywords: Knee muscle strength, underwater dolphin kick, ankle flexibility, male, Bayesian approach

DOI: 10.3233/IES-200255

Journal: Isokinetics and Exercise Science, vol. 30, no. 1, pp. 61-68, 2022