title: Effect of imposing changes in kick frequency on kinematics during undulatory underwater swimming at maximal effort in male swimmers.
abstract: Undulatory underwater swimming (UUS) is an important swimming technique after a start and after turns. It was considered that a higher swimming velocity (U) resulted from a higher kick frequency (f), and greater propelling efficiency, i.e., Strouhal number (St) and Froude efficiency (ηF), resulted from a lower f. The aim of this study was to investigate whether changing f affected U and St, ηF plus other kinematics of UUS. Ten national-level male swimmers participated in the study. First, the swimmers performed maximal UUS (Pre; this f was defined as 100% F). Second, the swimmers synchronized their f with the sound of a metronome and with six frequencies (85% F, 90% F, 95% F, 105% F, 110% F, and 115% F) randomly presented. During the higher f sessions, kick amplitude (A) significantly decreased from Pre (115% F: -10.8%, p<.05); however, U was unchanged. In contrast, in lower f sessions, St and ηF were unchanged, but the wavelength per body length (λBL), which indicates UUS mode, significantly decreased (90% F: -1.3%, p<.05). In conclusion, these results suggest that increasing f for UUS would not affect U, but a decrease in f may be suitable for human undulation training.
authors.affiliation: Graduate School of Comprehensive Human Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8574, Japan. Electronic address: sashimimasayo0727@gmail.com.
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Shimojo
authors.affiliation: Faculty of Health and Sport Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8574, Japan. Electronic address: sengoku@taiiku.tsukuba.ac.jp.
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Sengoku
authors.affiliation: Graduate School of Engineering, Iwate University, 3-18-8 Ueda, Morioka, Iwate 020-8550, Japan. Electronic address: tmiyoshi@iwate-u.ac.jp.
authors.forename: Tasuku
authors.initials: T
authors.lastname: Miyoshi
authors.affiliation: Faculty of Health and Sport Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8574, Japan. Electronic address: tsubaki@taiiku.tsukuba.ac.jp.
authors.forename: Shozo
authors.initials: S
authors.lastname: Tsubakimoto
authors.affiliation: Faculty of Health and Sport Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8574, Japan. Electronic address: takagi@taiiku.tsukuba.ac.jp.
authors.forename: Hideki
authors.initials: H
authors.lastname: Takagi
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D001835:Body Weight; D006801:Humans; D007101:Immersion; D008297:Male; D011597:Psychomotor Performance / Q000502:physiology*; D013550:Swimming / Q000502:physiology*; D014867:Water; D055815:Young Adult
chemical_list: D014867:Water
keywords: Dolphin kick; Froude efficiency; Strouhal number; Swimming velocity