WAVE CHARACTERISTICS OF BUTTERFLY SWIMMING

Citation
Rh. Sanders et al., WAVE CHARACTERISTICS OF BUTTERFLY SWIMMING, Journal of biomechanics, 28(1), 1995, pp. 9-16
Citations number
10
Categorie Soggetti
Engineering, Biomedical",Biophysics
Journal title
ISSN journal
00219290
Volume
28
Issue
1
Year of publication
1995
Pages
9 - 16
Database
ISI
SICI code
0021-9290(1995)28:1<9:WCOBS>2.0.ZU;2-P
Abstract
In this study it was hypothesized that elite butterfly performance is characterized by wave motions with particular frequency, amplitude, an d phase characteristics. Particular emphasis was accorded the question of whether 'waves' travel along the body during the butterfly stroke. Selected body landmarks and the center of mass (CM) of eight elite ma les and eight elite female swimmers were quantified. Fourier analysis was conducted to determine the frequency, amplitude, and phase charact eristics of the vertical undulations of the vertex of the head, should ers, hips, knees, and ankles, The differences in phase between these l andmarks for the first (H1) and second (H2) Fourier frequencies were i nvestigated to establish whether waves travelled along the body in a c audal direction. The absolute average velocity of H1 wave travel from vertex to ankle was found to be a mean of 0.34 m s(-1) faster than the forward velocity of the CM for the male swimmers and 0.17 m s(-1) fas ter for the female swimmers. There was a very strong relationship (p < 0.01) between velocity of H1 wave travel and CM velocity. There was n o evidence to suggest that elite swimmers timed their actions to minim ise vertical CM displacement to reduce mechanical work. In fact, the p hase relationships among adjacent segments suggested that energy gaine d by raising the CM was transmitted caudally and contributed to a prop ulsive 'whip-like' action.