title: Wave characteristics in breaststroke technique with and without snorkel use.
abstract: The purpose of this paper was to examine the characteristics of waves generated when swimming with and without the use of Aquatrainer® snorkels. Eight male swimmers performed two maximal bouts of 25 m breaststroke, first without the use of a snorkel (normal condition) and then using a snorkel (snorkel condition). The body landmarks, centre of the mass velocity, stroke rate, stroke length, stroke index, and Strouhal number (St) were quantified. Fourier analysis was conducted to determine the frequency, amplitude, and phase characteristics of the vertical undulations. We also determined the undulation period, the first and second harmonic wave percentage, and the contribution of these components to the power of each of the wave signals. The first wave harmonics had a frequency of 0.76 Hz (normal condition) and 0.78 Hz (snorkel condition), and the second wave harmonics had a frequency of 1.52 Hz (normal condition) and 1.56 Hz (snorkel condition). Under the normal conditions, the wave amplitude was higher on the vertex (0.72 m) and cervical (0.32 m) than that produced under snorkel conditions (0.71 m and 0.28 m, respectively). The lowest values were found in the hip (0.03 m in normal conditions, and 0.02 m in snorkel conditions) and in the trunk (0.06 m in normal conditions, and 0.04 m in snorkel conditions). It can be concluded that snorkel use seems to lead to slight changes in the biomechanical pattern in swimming velocity, as well as several stroke mechanical variables.
authors: Sport Sciences School of Rio Maior, Rio Maior, Portugal. ; Research Center in Sports Science, Health and Human Development, Vila Real, Portugal.
authors: Ana
authors: A
authors: Conceição
authors: University of Trás-os-Montes and Alto Douro, Vila Real, Portugal. ; Research Center in Sports Science, Health and Human Development, Vila Real, Portugal.
authors: António J
authors: AJ
authors: Silva
authors: INESC TEC - INESC Technology and Science (formerly INESC Porto) and ECT - School of Science and Technology, University of Trás-os-Montes e Alto Douro, Portugal.
authors: José
authors: J
authors: Boaventura
authors: Research Center in Sports Science, Health and Human Development, Vila Real, Portugal. ; University of Beira-Interior, Covilhã, Portugal.
authors: Daniel A
authors: DA
authors: Marinho
authors: Sport Sciences School of Rio Maior, Rio Maior, Portugal. ; Research Center in Sports Science, Health and Human Development, Vila Real, Portugal.
authors: Hugo
authors: H
authors: Louro
keywords: Fourier analysis; competitive swimming; stroke length; stroke rate; swimming snorkel; wave motion