Sprint and distance swimmers: the same animal?

In this talk the techniques of sprint and distance swimmers are discussed with a view to informing coaches of the similarities and differences between these groups. In the past it has been reported that sprint and distance swimmers are different in several aspects of technique. However, previous comparisons were at the respective race pace and sprint and distance specialists have not been compared when swimming at the same pace. Therefore it is difficult for coaches to know whether to teach the swimmers the same way when developing good technique. This talk presents new information based on recent scientific research conducted at the Centre for Aquatics Research and Education (CARE). The variables of interest were: average swim speed, stroke length, stroke frequency, stroke index, hand stroke pattern, foot range of motion, elbow angle, shoulder and hip roll angle and stroke phase durations. Interesting and unexpected findings emerged that have implications for the way specialist sprint and distance swimmers should be coached

Reliability of Three-Dimensional Angular Kinematics and Kinetics of Swimming Derived from Digitized Video

The purpose of this study was to explore the reliability of estimating three-dimensional (3D) angular kinematics and kinetics of a swimmer derived from digitized video. Two high-level front crawl swimmers and one high level backstroke swimmer were recorded by four underwater and two above water video cameras. One of the front crawl swimmers was digitized at 50 fields per second with a window for smoothing by a 4(th) order Butterworth digital filter extending 10 fields beyond the start and finish of the stroke cycle (FC1), while the other front crawl (FC2) and backstroke (BS) swimmer were digitized at 25 frames per second with the window extending five frames beyond the start and finish of the stroke cycle. Each camera view of one stroke cycle was digitized five times yielding five independent 3D data sets from which whole body centre of mass (CM) yaw, pitch, roll, and torques were derived together with wrist and ankle moment arms with respect to an inertial reference system with origin at the CM. Coefficients of repeatability ranging from r = 0.93 to r = 0.99 indicated that both digitising sampling rates and extrapolation methods are sufficiently reliable to identify real differences in net torque production. This will enable the sources of rotations about the three axes to be explained in future research. Errors in angular kinematics and displacements of the wrist and ankles relative to range of motion were small for all but the ankles in the X (swimming) direction for FC2 who had a very vigorous kick. To avoid large errors when digitising the ankles of swimmers with vigorous kicks it is recommended that a marker on the shank could be used to calculate the ankle position based on the known displacements between knee, shank, and ankle markers

A temporal investigation into the butterfly kick placement following a breaststroke start and turn

The purpose of this study was to determine whether an early or late placement of the butterfly kick during the arm pull-down is more effective in terms of breaststroke start and turn performance between female and male swimmers. Overall the timing of the kick placement does not appear to influence the effectiveness of the underwater phase following a breaststroke start or turn. Therefore the style selected by swimmers may be as a result of individual preference. Females overall start performance was improved by using an early placement

Effects of 50m and 400m Race Paces on Three-Dimensional Kinematics and Linear Kinetics of Sprint and Distance Front Crawl Swimmers

Many authors have proposed that sprint and distance front crawl swimmers differ in their stroke characteristics, however little three-dimensional quantitative data is provided to support these assumptions. It is currently unknown whether sprint and distance swimmers exhibit distinct stroke characteristics when swimming at the same pace. There were two main purposes of this study: 1) to determine whether there are distinct kinematic and kinetic differences between sprint and distance front crawl swimmers, and 2) to investigate whether stroke characteristics of front crawl swimmers, in terms of kinematic and kinetic variables change with swimming speed. Fifteen male national/international front crawl swimmers (17.87 +/- 2.33yrs; 73.87 +/- 8.72kg; 183.02 +/- 6.84cm) volunteered to participate in this study. This sample was composed of seven sprint (SG) and eight distance (DG) swimmers. Each testing session required swimmers to perform four 25m sprints and one 400m max effort (front crawl), with no pacing strategy, in a randomised order. Each trial was performed through a 6.75m3 calibrated space and recorded by six gen-locked JVC KY32 CCD cameras (4 below and 2 above water) sampling at a frequency of 50 fields per second. All trials were processed using ‘APAS’ software to obtain 3D coordinate data. Anthropometric measures were quantified using the elliptical zone method. Both data sets were entered into a bespoke MATLAB program which output: average swim velocity (Vav), stroke length (SL), stroke frequency (SF), stroke index (SI), vertical and lateral displacement for each segment, shoulder and hip roll angle, and elbow joint angle variables (1st back, shoulder x, end back, hand exit and recovery elbow angle). Stroke phase (entry, pull, push and recovery) durations (%) were quantified at instants corresponding to percentiles of the stroke cycle. Centre of mass position data were obtained from the digitised 3D data using a 14 segment rigid link body model in conjunction with the body segment parameter data obtained by the elliptical zone method. Component whole body velocity (VCOMHor), acceleration (accCOM) and net force (forceCOM) were derived from the centre of mass position data. Variables were statistically analysed in SPSS v.14.0, using a General Linear Model, repeated measures analysis of variance. The results indicated that the groups differed (p<0.05) with respect to the duration of the pull phase, the occurrence of max left and right shoulder roll and the temporal sequencing of the shoulders and hips rolling at both sprint and distance pace. Other variables approached significance between the groups, particularly when distance swimming, such as the duration of the push phase (p=0.082), the Vav (p=0.071) and average VCOMHor (p=0.071). The stroke kinematic variables that changed between paces (p<0.05) were the duration of the entry, pull, push, hand exit and recovery phases; the elbow angle at the end back position and the push phase range; total shoulder and hip roll; the sum average vertical displacement of the foot; the time to max vertical and lateral displacement of the finger; the time at max right elbow extension; the average VCOMHor, Min VCOMHor and Max VCOMHor. The stroke kinetic variables that changed between paces (p<0.05) were the Min accCOM, Max accCOM, range of accCOM, min forceCOM and max forceCOM. Other variables approached significance between the paces such as the entry elbow angle (p=0.084), the max right elbow extension (p=0.056), the finger lateral range (p=0.067) and the time to max accCOM (p=0.079). The SG displayed shorter durations of the pull and push phases than the DG for both paces, which was linked to the faster horizontal velocity and/or vertical acceleration of the hand. The sequencing order of the shoulders and hips changed between groups and paces, which was speculated to be controlled by the magnitude of the leg-kick. The main changes between paces were the greater magnitude of elbow angle at both the end back position and the push phase range, which contributed to the adjustment of kinetic variables. SL, SF, SI, Vav and the duration of the all the stroke phases changed between sprint and distance pace in order to meet the physiological requirements of the race distance. The prolonged duration of the entry phase, when distance swimming, resulted in a delayed attainment of the catch position and maximum stroke depth. Moreover, the magnitude of shoulder and hip roll increased at distance compared to sprint pace, which in turn influenced the magnitude of average vertical and range of lateral displacement of the finger between paces. In conclusion, contrary to the literature, SG and DG differed only with respect to the duration of the pull and push stroke phases and the sequencing order of the shoulders and hips. All swimmers adjust the majority of kinematic and kinetic variables depending on the swim pace in order to optimise performance for that race distance

MAGNITUDE OF MAXIMUM SHOULDER AND HIP ROLL ANGLES IN BACK CRAWL AT DIFFERENT SWIMMING SPEEDS

The purpose of this study was to identify the characteristics of maximum shoulder and hip roll angles in back crawl at different swimming speeds. Ten male elite swimmers performed back crawl at four different swimming speeds. The swimming trials were filmed by a total of six digital video cameras and three-dimensional coordinates of swimmer's anatomical landmarks were calculated using the three-dimensional direct linear transform. The data were input to a MATLAB programme to calculate linear and angular kinematics. Among the four speed trials, maximum shoulder and hip roll angles were unchanged, and maximum shoulder roll angle was significantly larger than maximum hip roll angle in all trials. In conclusion, the swimming speed does not affect swimmer's shoulder and hip roll angles in back crawl swimming