Journal of Applied Biomechanics
High-level swimmers kinematic efficiency during the underwater phase of a grab start
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Manuscript ID: Manuscript Type:
draft Technical Note
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Keywords:
Journal of Applied Biomechanics
swimming performance, start, underwater, kinematic energy
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Re Human Kinetics, 1607 N Market St, Champaign, IL 61825
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Journal of Applied Biomechanics
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Title:
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underwater phase of a grab start
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Authors:
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Affiliations:
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swimmers
kinematic
efficiency
during
the
Elipot, M.1,2, Dietrich, G.2, Hellard, P.1, Houel, N.1
Département Recherche Fédération Française de Natation, Pôle Natation
INSEP, 11 Avenue du Tremblay, 75012 Paris, France. 2
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High-level
Laboratoire Ergonomie Comportement et Interaction, EA 4070 – LAMA,
Université Paris Descartes, France.
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Type of manuscript: Technical note.
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Key words: swimming performance, start, underwater, kinematic energy.
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Email:
[email protected]
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Mailing address:
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Phone number: +33 610 32 06 75
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Number of tables: 3.
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Number of figures: 3.
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Number of words (main text): 1890 (max: 2000).
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Number of words (abstract): 190 (between 150 and 200).
Human Kinetics, 1607 N Market St, Champaign, IL 61825
Journal of Applied Biomechanics
ABSTRACT The purpose of the present work was to study swimmers’ efficiency during the underwater
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phase of the grab start. Eight high-level swimmers participated in this study. They performed
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two types of start: a regular grab start (with underwater leg propulsion after the glide) and a
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grab start with no underwater movement (swimmers had to remain in a streamlined position).
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Four cameras filmed the entire underwater phase of all starts. Nine anatomic landmarks were
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identified on the swimmers’ bodies and their positions were calculated using a modified
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double plan DLT technique. From these positions and Dempster’s anthropometric data, the
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centre of mass position and velocity were also determined. Kinematic energies were also
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calculated. This velocity and kinematic energies for the two types of start were compared.
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Swimmers began underwater leg propulsion 1.69 m too soon. The global and external
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energies were significantly higher for the start with underwater leg propulsion. Nevertheless,
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swimmers’ velocities were equivalent for both starts. These results suggest that the swimmers
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did not use the underwater phase of the start efficiently: By kicking too soon, they did not
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succeed in producing higher velocities and thus wasted energy.
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INTRODUCTION The start is an important part of swimming events. It can account for 0.5 and 11% of the total
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event time, as observed for the 1000-yard and 50-yard freestyle events, respectively (Hay,
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1986). The importance of the start is further emphasised by the observation that the
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differences between the individual performances of high-level swimmers are quite small. For
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example, during the 50-m freestyle event at the Athens Olympic Games (2004), the difference
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between the three Olympic medallists was only 0.11 s at the end of the race but had already
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reached 0.1 s at the 15th meter. Differences in starting efficiency could explain nearly all of
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the small differences in final time.
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Start performance is defined as the performance observed between the start signal and the
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moment when the swimmer’s head reaches the 10th (Alves, 1993; Arellano et al., 1996) or the
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15th meter (Mason & Cossor, 2000; Issurin & Verbitsky, 2002). The global analysis of starts
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has shown that the underwater phase is determinant to achieve a good start performance
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(Clothier et al., 2000; Cossor & Mason, 2001; Shin & Groppel, 1986). Guimaeres & Hay
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(1985) showed that 95% of the differences observed between swimmers’ starts could be
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explained by differences in the underwater phase, yet surprisingly few studies have focused
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on this phase (Blanksby et al., 1996; Lyttle et al., 1998; Clothier et al., 2000; Lyttle et al.,
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2000).
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The underwater phase of the start is divided into the glide and underwater undulatory
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swimming. An optimised underwater phase aims to maintain the velocity created during the
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aerial phase up to the resumption of arm stroking. To achieve the best performance, the
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transition between the glide and underwater undulatory swimming is determinant (Lyttle et
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al., 2000). Blanksby et al. (1996) showed that swimmers can lose time by kicking too late or
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too soon after the glide phase. Swimmers starting underwater undulatory swimming too soon
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Human Kinetics, 1607 N Market St, Champaign, IL 61825
Journal of Applied Biomechanics
would create higher hydrodynamic resistance and would lose speed. Although these studies
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pointed out the benefits of an efficient underwater phase, none of them presented the optimal
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conditions for an efficient start.
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During the underwater phase of a start, swimmers create hydrodynamic resistances
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(Karpovich, 1933) that are directly influenced by the velocity and depth (Lyttle et al., 1998;
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Lyttle et al., 2000; Toussaint et al., 2002; Vennel et al., 2006). Hertel (1966) and Larsen et al.
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(1981) showed that the coefficient of drag decreases rapidly as the swimmer’s body depth
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increases. Vennel et al. (2006) showed that at underwater swimming velocities (i.e. about 2
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m.s-1) hydrodynamic resistances are 2.4 times smaller when the swimmer is fully immersed.
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The kinematic energy expended by athletes during sport performance has often been
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calculated as a means to assess their movement efficiency (Winter, 1990; Duboy, 1994)
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With Eg: The global kinematic energy
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Ei: The internal kinematic energy
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Ee: The external kinematic energy
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Ii: Segment mass moment of inertia
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ωi: Segment transversal rotation velocity
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mi: Segment weight 22
VGi/R*: Segment centre of mass velocity expressed in the centre of mass frame of reference
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VG/R: Body centre of mass velocity expressed in the global Galilean frame of reference. To our knowledge, however, this variable has never been used to study swimmer efficiency
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during the underwater phase of the start.
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Although some investigations have sought to optimise the underwater phase of the start, the
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efficiency of swimmers during this phase remains unknown. The aim of the present work was
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to study the swimmer efficiency during the underwater phase of the start. METHODS Eight high-level swimmers voluntarily participated in this study (Table 1). All were informed
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of the objectives and signed a consent form. The swimmers were asked to perform grab starts
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as efficiently as possible. They practised this type of start on a regular basis and used it for
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competitive racing. The swimmers had to perform six grab starts. Three starts had to be
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performed without any subsequent propulsion during the underwater phase of the start.
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During this phase, the swimmers maintained the streamlined position with no further
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propulsive movement. Three regular grab starts had then to be performed (i.e. with
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underwater leg propulsion). For each condition, the best start was analysed.
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Four mini-DV cameras (Panasonic NV-GS17 and Sony DCR-HC20E) were used to record the
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entire underwater phase of the start, i.e. from the start wall to the 15th meter. Three cameras
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(camera 1, 2 and 3) were placed behind portholes and the fourth was placed in waterproof
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housing (Figure 1). The cameras were positioned so as to minimise optical refraction effects
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(Snell’s law) (Kwon, 1999; Kwon & Casebolt, 2006): A large distance separated the cameras
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and the centre filmed zone. The optical axes of the cameras were perpendicular (± 5°) to the
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air-water interface plane. The angles between the principal axis of camera 1 and the other
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cameras were between 55° and 70°.
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The underwater experimental area was divided into three field of view measuring 5 × 2 × 2 m:
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The first zone was from the start wall to the 5th meter, the second zone from the 5th to the 10th
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meter, and the third zone from the 10th to the 15th meter. To limit the effects of image
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distortion (due to camera lens deformations) on reconstruction accuracy, particularly maximal
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Human Kinetics, 1607 N Market St, Champaign, IL 61825
Journal of Applied Biomechanics
error reconstruction, only the points within the 2/3 centre of the camera field were
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reconstructed (Figure 1). The sampling frequency was 25 frames per second. The video was
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interlaced scan and the odd and even fields were used. The cameras were synchronised using
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light signal.
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The entire underwater phase was recorded (i.e. from the instant at which the swimmers were
6
completely under water until the instant they broke the water surface, stopped gliding or
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began arm propulsion).
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To minimise errors during the digitizing process, the two sides of the swimmer’s body were
9
assumed to be symmetric. Only the right side was digitalized. Nine anatomic landmarks were
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identified on the swimmers: a toe, the lateral malleolus, the knee, the iliac spine, the
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acromion, a finger tip, the wrist, the elbow, and the centre of the head. A modified double
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plane direct linear transformation method (inspired from Drenk et al., 1999) was used to
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calculate the landmark coordinates in space. Space reconstruction accuracy was calculated as
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described by Kwon & Casebolt (2006) and was 6.2 mm (maximal reconstruction error was
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12.2 mm). These positions, together with Dempster’s anthropometric data (1959), were used
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to determine the trajectory of the centre of mass. Data were filtered with a Butterworth II
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filter (Winter, 1990). Cut-off frequencies were included between 5 and 7 Hz.
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During the entire underwater phase of the start, each swimmer’s centre of mass depth and
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velocity and swimmer’s kinematic energy were calculated.
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The results obtained (velocities, depths, external and internal kinematic energies) for starts
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with and without underwater leg propulsion were compared using one-way analysis of
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variance for repeated measures. These comparisons were made at specific instants (Figure 2):
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At T0, i.e. the instant at which the swimmer’s body was fully immersed.
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At Tini, i.e. the instant when the swimmer initiated underwater leg propulsion.
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Once leg propulsion began, every 0.5 m up to 3 m (Tini + 3 m) (6 comparisons). The centre of mass position was used to identify these positions.
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The compared parameters were the internal, external and global kinematic energies, the centre
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of mass velocity and depth, and the position and velocity at T0. The effect of underwater
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propulsion on depth was analysed using two-way analysis of variance for repeated measures.
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All statistical tests were performed with a level of confidence set at 99% (p < 0.01).
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RESULTS
Table 2 shows the optimal distance (from the start wall) for initiating underwater leg
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propulsion compared with the real distance at which the swimmers began propulsion. It
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appears that swimmers initiated underwater undulatory swimming 1.69 m too soon (SD =
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0.75).
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The comparison of the starts with and without underwater leg propulsion is presented in Table
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3. The analysis of variance revealed no significant difference in the distance covered at the
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instant of full immersion (DistT0) or the velocity at the same instant (VT0).
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The two starts significantly differed at each instant in terms of global kinematic energy (EgTX)
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and internal kinematic energy (EiTX), with the exception of the instant at which underwater
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leg propulsion began (Tini). The start with underwater leg propulsion showed significantly
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higher values than the start without propulsion.
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Significant differences between the two starts were also noted in the swimmers’ centre of
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mass velocity (VTX) and external kinematic energy (EeTX) 3 meters after underwater leg
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propulsion began (Tini + 3). At this instant, the start with underwater leg propulsion showed
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Human Kinetics, 1607 N Market St, Champaign, IL 61825
Journal of Applied Biomechanics
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significantly higher values than the start without. At the other instants, no significant
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differences were observed in these variables.
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Significant differences between the two starts were also observed at all instants for the
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swimmers’ centre of mass depth (DTX), with the exception of Tini and Tini + 0.5 m. The two-
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way analysis of variance revealed significant type of start–distance interactions from Tini + 1
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m (Figure 3). DISCUSSION
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Choosing the optimal instant to initiate underwater undulatory movement directly influences
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start performance. This choice has a direct impact on the decrease in underwater deceleration
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(caused by hydrodynamic resistance) and the decrease in energy expenditure (Lyttle et al.,
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2000).
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The combined results of the present study and the study of Lyttle et al. (2000) suggest that
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swimmers initiate underwater undulatory movement too soon. Our start comparison also
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showed that, at the first instant of full body immersion, the distance covered by the swimmers
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and their velocity seemed to be the same for starts with and without underwater leg
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propulsion (respectively, 3.8 m versus 3.73 m and 3.87 m.s-1 versus 3.61 m.s-1). Furthermore,
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none of the studied variables were significantly different at the instant when the swimmers
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initiated underwater undulatory movement (Table 3). This implies that the swimmers’ actions
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during the impulsion, aerial and gliding phases led to equivalent velocity, depth, and
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kinematic energy expenditure for the two types of start.
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In contrast, once underwater leg propulsion began, the swimmers’ global and internal
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kinematic energy expenditure was higher for the start with underwater leg propulsion. The
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swimmers did not, however, produce higher velocities and the external kinematic energy was
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equivalent. This indicates that the difference in global kinematic energy was due only to the
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internal kinematic energy difference. These results seem to suggest that the kinematic energy
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produced by all segment movements relative to the centre of mass did not contribute to centre
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of mass propulsion. This infers that, by beginning underwater undulatory movements too
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soon, the swimmers wasted energy.
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The results also showed that once underwater leg propulsion began, the swimmers’ depth
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quickly decreased. One meter after leg propulsion began, the type of start had an effect on the
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swimmer’s depth. Figure 3 shows that the start with underwater propulsion was characterised
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by quicker surface resumption. Previous studies of the hydrodynamic resistances of towed
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swimmers or mannequins have shown that hydrodynamic resistances are directly influenced
10
by centre of mass velocity and depth. Indeed, when the swimmers approach the water surface
11
with a high velocity, drag strongly increases (Hertel, 1966; Larsen et al., 1981; Lyttle et al.,
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1998; Toussaint et al., 2002; Vennel et al., 2006). By returning to the water surface too soon
13
(with too high velocity), swimmers are faced with higher hydrodynamic resistances. The
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energy waste observed in the present study could be explained by this effect of the start with
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underwater propulsion.
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In conclusion, the results of this study tend to suggest that swimmers do not use the
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underwater phase efficiently during competitive starts. Indeed, during underwater leg
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propulsion, the swimmers’ kinematic energy expenditure was higher during a glide velocities
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are the same.
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ACKNOWLEDGEMENTS 20
The authors wish to thank the “Ministère de la Jeunesse, des Sports et de la Vie Associative”
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and the “Fédération Française de Natation” for financing this study. The authors also wish to
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thank Frédéric Frontier, Frédéric Clerc, Isabelle Amaudry and the “INSEP” for logistic
Human Kinetics, 1607 N Market St, Champaign, IL 61825
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support, and Jean-Lyonel Rey, Stéphane Lecat, Eric Boissière and Yves Thomassin for their
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contributions. REFERENCES Alves, F. (1993). Analysis of swimming races. Proceedings of the XIVth Congress of
4
International Society of Biomechanics (pp. 88-89). Paris, France: International Society of
5
Biomechanics.
6
Arellano, R., Moreno, F. J., Martinez, M., & Ona, A. (1996). A device for quantitative
7
measurement of starting time in swimming. In J. P. Troup, A. P. Hollander, D. Strasse, S. W.
8
Trappe, J. M. Cappaert, & T. A. Trappe (Eds.), Biomechanics and Medicine in Swimming VII
9
(pp. 195-200). London, United Kingdom: E & FN Spon.
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3
Blanksby, B. A., Gathercole, D. G., & Marshall, R. N. (1996). Force plate and video analysis
11
of the tumble turn by age-group swimmers. Journal of Swimming Research, 11, 40-45.
12
Issurin, V. B., & Verbitsky, O., 2002. Track start vs. Grab start: evidence of the Sydney
13
Olympic Games. In J. C. Chatard (Ed.), Biomechanics and Medicine in Swimming IX (pp. 92).
14
Saint Etienne, France: Université de Saint-Etienne.
15
Clothier, P. J., Mac Elroy, G. K., Blansby, B. A., & Payne, W. R. (2000). Traditional and
16
modified exits following freestyle tumble turns by skilled swimmers. South African Journal
17
for Research In Sport Physical Education and Recreation, 22, 41-55.
18
Cossor, M. J., & Mason, B. R. (2001). Swim start performances at the Sydney 2000 Olympic
19
Games. In J. R. Blackwell (Ed.), Proceedings of XIX International Symposium on
20
Biomechanics in Sports (pp. 65-69). San Francisco, California: University of San Francisco.
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Dempster, W. T., Gabel, W. C., & Felts, W. J. L. (1959). The anthropometry manual work
2
space for the seated subject. American Journal of Physiology and Anthropometry, 17, 289-
3
317.
4
Drenk, V., Hildebrand, F., Kindler, M., & Kliche, D. (1999). A 3D video technique for
5
analysis of swimming in a flume. In R. H. Sanders, & B. J. Gibson (eds.), Proceedings of the
6
XVII International Symposium on Biomechanics in Sports (pp. 361-364). Perth, Australia:
7
Edith-Cowan University.
8
Gamaraes, A., C., S., & Hay, J., G. (1985). A kinematic analysis of the grab starting technique
9
in swimming. International Journal of Sport Biomechanics, 1, 25-35.
rP
Fo
1
Hay, J. G. (1986). Swimming biomechanics: a brief review. Swimming technique, 23, 15-21.
11
Hertel, H. (1966). Structure-Form-Movement. New York, New Jersey: Reinhold Publishing
12
Corporation.
13
Karpovich, P. V. (1933). Water resistance in swimming. Research Quarterly, 4, 21-28.
14
Kwon, Y. H. (1999). Object plane deformation due to refraction in two-dimensional
15
underwater motion analysis. Journal of Applied Biomechanics, 15, 396-403.
16
Kwon, Y. H., & Casebolt, J. B. (2006). Effects of light refraction on the accuracy of camera
17
calibration and reconstruction in underwater motion analysis. Sports Biomechanics, 5, 95-120.
18
Larsen, O., W., Yancher, R., P., & Baer, C., L., H. (1981). Boat design and swimming
19
performance. Swimming Technique, Aug-Oct, 38-44.
20
Lyttle, A., D., Blanksby, B., A., Elliott, B., C., & Lloyd, D., G. (1998). The role of drag in the
21
streamlined glide. Journal of Swimming Research, 13, 15-22.
iew
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Journal of Applied Biomechanics
Page 12 of 19
Lyttle, A., D., Blanksby, B., A., Elliott, B., C., & Lloyd, D., G. (2000). Net forces during
2
tethered simulation of underwater streamlined gliding and kicking techniques of the freestyle
3
turn. Journal of Sports Sciences, 18, 801-807.
4
Mason, B., & Cossor, J. (2000). What can we learn from competition analysis at the 1999 Pan
5
Pacific Swimming Championships? In R. Sanders & Y. Hong (Eds.), Proceedings of XVIII
6
Symposium on Biomechanics in Sports (pp. 75-82). Hong Kong, China: The Chinese
7
University of Hong Kong.
8
Shin, I., & Groppel, J. (1986). A comparison of the grab start and track start as utilized by
9
competitive swimmers. In D. L. Landers (Ed.), Sport and Elite Performers (pp. 171-175).
rP
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Champaign, Illinois: Human Kinematics Publishers.
11
Toussaint, H., M., van Stralen, M, & Stevens, E. (2002). Wave drag in front crawl swimming.
12
In Gianikellis, K. (Ed.), Proceedings of the XXth International Symposium on Biomechanics
13
in Sports (pp. 279-282). Extremadura, Spain: Universidad de Extremadura.
14
Vennell, R., Pease, D., & Wilson, B. (2006). Wave drag on human swimmers. Journal of
15
Biomechanics, 39, 664-671.
16
Winter, D., A. (2000). Biomechanics and motor control of human movement. New York, New
17
Jersey: A. Wiley-Interscience Publication.
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List of tables
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Tables 1 - Swimmers’ general characteristics
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Tables 2 - Lag between the optimal instant to initiate underwater leg propulsion and the
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instant at which swimmers really began leg propulsion
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Table 3 - Comparison between the start with underwater leg propulsion and the start without
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underwater leg propulsion
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List of figures
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Figure 1 - Experimental set-up
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Figure 2 - Comparison between the two types of start: With and without leg propulsion
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Figure 3 - Interaction effect of the distance covered and the type of start on the swimmer’s
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depth
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Tables
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Table 1
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Swimmers’ general characteristics
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Mean SD
Best performances (s) 50-m 100-m Body mass Height (m) 50-m freestyle (% 100-m freestyle (% (kg) freestyle (s) of the world freestyle (s) of the world record) record) 1.85 78.5 24.41 114.7 51.84 110 0.05 4.66 1.62 7.49 1.49 3.12
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Table 2:
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Lag between the optimal instant to initiate underwater leg propulsion and the instant at which
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swimmers really began leg propulsion
Distance at which Optimal distance to swimmers really initiated initiate underwater leg underwater leg propulsion propulsion (m)* (m) 4.9 4.28 3.81 3.97 4.82 3.51 3.82 3.59
-0.51 -0.97 -1.85 -1.83 -1.85 -2.09 -1.44 -2.99
4.09 0.53
-1.69 0.75
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Mean SD
5.41 5.25 5.66 5.8 6.67 5.6 5.26 6.58
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Subject 1 Subject 2 Subject 3 Subject 4 Subject 5 Subject 6 Subject 7 Subject 8
Lag (m)
The distance were calculated from the start wall
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* i.e. when the swimmer's centre of mass reached a velocity between 2.2 and 1.9 m.s-1 (Lyttle et al, 1998)
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Table 3
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Comparison between the start with underwater leg propulsion and the start without
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underwater leg propulsion Start without underwater undulatory movements
Start with underwater undulatory movements
Comparison
SD
Mean
SD
F
p
DistT0 VT0
3.8 3.87
0.26 0.55
3.73 3.61
0.19 0.31
0.33 1.3
n.s n.s
VTini VTini + 0.5 VTini + 1 VTini + 1.5 VTini + 2 VTini + 2.5 VTini + 3
3.36 2.93 2.53 2.19 1.91 1.68 1.51
0.49 0.52 0.46 0.39 0.33 0.3 0.27
3.11 2.7 2.46 2.18 2.07 1.95 1.92
0.44 0.41 0.29 0.3 0.24 0.23 0.2
1.13 0.95 0.13 0.004 1.29 3.77 10.18
n.s n.s n.s n.s n.s n.s s
DTini DTini + 0.5 DTini + 1 DTini + 1.5 DTini + 2 DTini + 2.5 DTini + 3
-0.92 -0.97 -1.03 -1.05 -1.06 -1.06 -1.04
0.18 0.15 0.12 0.14 0.16 0.18 0.2
-0.73 -0.82 -0.87 -0.85 -0.79 -0.73 -0.65
0.12 0.09 0.08 0.13 0.13 0.21 0.25
5.53 11.26 15.37 12.14 11.48 27.42 31.7
n.s n.s s s s s s
EgTini
34515
11546
56615
15548
2.44
n.s
EgTini + 0.5
15419
7988
36897
12709
14.79
s
EgTini + 1
9794
5100
32509
10506
30.26
s
EgTini + 1.5
7063
3832
32842
33.77
s
EgTini + 2
2741
32279
11767
40.48
s
EgTini + 2.5
4363
2138
32533
13228
30.93
s
EgTini + 3
3505
1643
322891
13758
31.48
s
EiTini
34050
11247
rR
11946
5100
56158
16548
2.444
n.s
EiTini + 0.5
15070
7990
36552
12747
14.72
s
EiTini + 1
9516
5118
32171
10509
30.04
s
EiTini + 1.5
6838
3853
32547
11963
EiTini + 2
4913
2761
32013
EiTini + 2.5
4205
2152
32292
EiTini + 3
3367
1657
32811
EeTini
464
148
457
EeTini + 0.5
348
105
389
EeTini + 1
278
73
EeTini + 1.5
224
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Mean
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s
40.07
s
13250
30.64
s
14074
30.21
s
108
0.01
n.s
92
0.64
n.s
338
70
2.81
n.s
60
294
59
5.36
n.s
EeTini + 2
190
50
266
55
8.23
n.s
EeTini + 2.5
167
55
231
57
4.48
n.s
EeTini + 3
138
40
223
50
12.12
s
iew
33.47
11789
With: DistT0 (m): The distance from the start wall when the swimmer is fully immersed -1
VTX (m.s ): The swimmer's velocity at T0, Tini, Tini + 0.5, 1, 1.5, 2, 2.5 and 3m DTx (m): The swimmer's depth at T0, Tini, Tini + 0.5, 1, 1.5, 2, 2.5 and 3m EgTX (J): The global mechanical energy at Tini, Tini + 0.5, 1, 1.5, 2, 2.5 and 3m EiTX (J): The internal mechanical energy at Tini, Tini + 0.5, 1, 1.5, 2, 2.5 and 3m
4
EeTX (J): The external mechanical energy at Tini, Tini + 0.5, 1, 1.5, 2, 2.5 and 3m
Human Kinetics, 1607 N Market St, Champaign, IL 61825
Page 17 of 19
Journal of Applied Biomechanics
1
Figures
2
Figure 1
3
Experimental set-up
5m
0m Zone 1
10 m Zone 2
15 m Zone 3
Start wall
rP
Fo Camera 4
Camera 1
Camera 2
: 2/3 centre of the camera field
4
iew
: Set of four calibration points
Camera 3
ev
Behind portholes
rR
ee
In waterproof housing
Human Kinetics, 1607 N Market St, Champaign, IL 61825
Journal of Applied Biomechanics
Page 18 of 19
1
Figure 2
2
Comparison between the two types of start: With and without leg propulsion Start wall First comparison
Second comparison
Third comparison
Start with underwater leg movements
etc
T0 :
rP
Fo
Start without any underwater movement
7
iew
6
Beginning of underwater undulatory swimming
ev
5
Dini + 0.5 m
rR
4
Dini
ee
The swimmer is fully immerged
3
Sixth comparison
8
9
10
11
12
Human Kinetics, 1607 N Market St, Champaign, IL 61825
Dini + 3 m
Page 19 of 19
Journal of Applied Biomechanics
1
Figure 3
2
Interaction effect of the distance covered and the type of start on the swimmer’s depth
-0,5 Tini
Tini + 0.5 m Tini + 1 m Tini + 1.5 m Tini + 2 m
Tini 2.5 m
Tini + 3 m
-0,7
-0,8
-0,9
No significant interaction (distance-type of start) on swimmer's depth
Start with underwater undulatory movement
Significant interaction (distance-type of start) on swimmer's depth
iew
ev
rR
ee
-1,2
rP
-1
-1,1
3
Start without underwater undulatory movement
Fo
Swimmer's centre of mass depth
-0,6
Human Kinetics, 1607 N Market St, Champaign, IL 61825