Biomechanics and Medicine in Swimming XI

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Repeated measures general linear modelling tests were used to compare the changes in the relative durations of the Entry and Glide, Pull, Push and Recovery phases between the affected and unaffected arms and between the percentage swimming speeds. In all comparisons, the level of statistical significance was set at p < .05. results There were significant differences (p < .05) between the affected- and unaffected-arm for the relative durations of each arm stroke phase across the five percentage speed increments (Fig. 2). The affected-arm on average spent relatively longer in all arm stroke phases, with the exception of the Pull phase, when compared to the unaffected-arm. The mean relative duration of the Entry and Glide phase (A) for the affected and unaffected arms did not significantly change as the participants increased their swimming speed. While the unaffected-arm’s relative Entry and Glide phase duration remained relatively constant (23.2 ± 8.0% vs. 23.1 ± 6.8%, for 80% and 100% of SS max respectively) with an increase in swimming speed, there was a slight reduction in the affectedarm’s relative Entry and Glide phase duration between 80% and 100% of SS max (38.3 ± 9.5% vs. 36.2 ± 11.6%). The mean relative duration of the Pull phase (B) for the unaffectedarm, but not for the affected-arm, changed significantly (p < .05) as the participants increased their swimming speed. While the affected-arm’s relative Pull phase duration remained relatively unchanged (10.9 ± 2.8% vs. 11.0 ± 2.3%, for 80% and 100% of SS max respectively) with an increase in swimming speed, there was a significant reduction (p < .05) in the unaffected-arm’s relative Pull phase duration between 80% and 100% of SS max (23.1 ± 5.9% vs. 20.5 ± 4.9%). The mean relative duration of the Push phase (C) for both the affected and unaffected arms changed significantly (p < .05) as the participants increased their swimming speed. At 80% of SS max , the mean Push phase durations were 18.4 ± 6.4% and 13.8 ± 2.7% for the affected- and unaffected-arm respectively. At 100% of SS max , the mean Push phase durations were 19.4 ± 5.3% and 15.4 ± 3.9% for the affected- and unaffected-arm respectively. The mean relative duration of the Recovery phase (D) for the affected and unaffected arms did not significantly change as the participants increased their swimming speed. Figure 2. Means and standard deviations of relative arm stroke phase durations for both the affected- and unaffected-arms (* Differences between arms are statistically significant p < .01). Bold bars indicate affected-arm. dIscussIon The purpose of this study was to determine whether the arm stroke phases used by competitive unilateral arm amputee front crawl swim- chaPter2.Biomechanics mers differed between their affected and unaffected sides and whether these phases changed with an increase in swimming speed. At all swimming speeds, the stroke phases of the affected and unaffected arms differed significantly. Whilst all swimmers pulled their affected-arm through the water fastest, the affected-arm on average spent relatively longer in all arm stroke phases, with the exception of the Pull phase, when compared to the unaffected-arm. Unfortunately, it is not possible to directly compare these findings with those for able-bodied swimmers or other swimmers with various loco-motor disabilities, since arm stroke phases are only reported in the literature as mean values of both arms (e.g., Chollet et al., 2000; Potdevin et al., 2006; Satkunskiene et al., 2005). As a consequence of their physical impairment, at all swimming speeds the arm amputees used an asymmetrical strategy for coordinating their affected-arm movement with their unaffected-arm. It was apparent that the amputees held their affected-arm stationary in the Entry and Glide phase before pulling it rapidly under the shoulder. As the affected-arm was then pushed towards the hip, its motion slowed before the Recovery phase commenced. Conversely, the amputees’ unaffectedarm moved steadily though the Entry and Glide phase and the Pull phase before being rapidly pushed into the Recovery phase. Such different bi-lateral motor control strategies might be linked to how these swimmers learnt to organise the motor skills necessary to swim front crawl. As swimming speed increased the relative durations of certain arm stroke phases changed. With increasing speed: 1) the affected-arm’s Entry and Glide phase decreased, while the unaffected-arm’s Entry and Glide phase remained unchanged; 2) the unaffected-arm’s Pull phase decreased, while the affected-arm’s Pull phase remained unchanged; and 3) both arms’ Push phase increased. Both Chollet et al. (2000) and Potdevin et al. (2006) showed that for able-bodied swimmers, the relative duration of the Entry and Catch phase (mean of both arms) decreased, while the relative durations of the Pull and Push increased with increasing swimming speed. The authors suggested that in making these adaptations, able-bodied swimmers were able to take advantage of longer periods of propulsive force application. In the current study propulsion was not measured. However, as a consequence of task (e.g., swimming faster), physical (e.g., single-arm amputation) and environmental (e.g., larger resistive forces at higher speeds) constraints, the unilateral arm amputee front crawl swimmers asymmetrically adjusted their arm movements to maintain the stable repetition of the overall arm stroke cycle. conclusIon The results from this study show that at all swimming speeds the stroke phases of the affected and unaffected arms differed significantly. The affected-arm on average spent relatively longer in all arm stroke phases, with the exception of the Pull phase, when compared to the unaffected arm. Such differences might be linked to how these swimmers learnt to organise the motor skills necessary to swim front crawl. As swimming speed increased, the duration of the affected-arm’s Entry and Glide phase and the unaffected-arm’s Pull phase significantly decreased, while the duration of both arms’ Push phase significantly increased. The arm amputees used a coordination strategy that asymmetrically adjusted their arm movements in order to maintain the stable repetition of their overall arm stroke cycle when swimming at different speeds. reFerences Chollet, D., Chalies, S., & Chatard, J.C. (2000). A new index of coordination for the crawl: Description and usefulness. International Journal of Sports Medicine, 21(1), 54-59. Maglischo, C.W., Maglischo, E.W., Higgins, J., Hinrichs, R., Luedtke, D., Schleihauf, R.E., & Thayer, A. (1988). A biomechanical analysis of the 1984 U.S. Olympic freestyle distance swimmers. In B.E. Ungerechts, K. Wilke, K. Reischle (Eds.), Swimming Science V, Champaign, IL: Human Kinetics, 351-360. 141
BiomechanicsandmedicineinswimmingXi Osborough, C.D., Payton, C.J., & Daly, D. (2009). Relationships between the front crawl stroke parameters of competitive unilateral arm amputee swimmers, with selected anthropometric characteristics. Journal of Applied Biomechanics, 25(4), 304-312. Potdevin, F., Bril, B., Sidney, M., & Pelayo, P. (2006). Stroke frequency and arm coordination in front crawl swimming. International Journal of Sports Medicine, 27(3), 193-198. Satkunskiene, D., Schega, L., Kunze, K., Birzinyte, K., & Daly, D. (2005). Coordination in arm movements during crawl stroke in elite swimmers with a loco-motor disability. Human Movement Science, 24(1), 54-65. AcKnoWledGeMents The authors would like to acknowledge the following: British Disability Swimming for their support in this project; Professor Ross Sanders for the use of his facilities at the Centre for Aquatics Research and Education, The University of Edinburgh; and Miss Casey Lee for her assistance during data collection. 142 Co-ordination Changes during a Maximal Effort 100 m Short Course Breaststroke Swim oxford, s. 1 , James, r. 1 , Price, M. 1 , Payton, c. 2 1 Coventry University, UK 2 Manchester Metropolitan University, UK The aim of the study was to establish the changes in co-ordination that occur during a 100 m breaststroke swim from a water start by: 1) measuring the kinematic changes that occur as the swimmer progressed through the four laps and, 2) analysing the co-ordination of the arms and legs (transition phase) corresponding to the time between the end of the leg propulsion and the start of the arm propulsion phases. Breaststroke participants (n=8, females and n=18, males) performed a 100 m maximal swim in a 25 m pool. They were recorded underwater using three 50 Hz cameras (one at each end of the pool and one mounted on a trolley). The last three strokes prior to turns were analysed. Significant changes in clean swim speed (p
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Figure 1. General biomechanical par
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average VO2 measured during resting
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Figure 2. Repeatability of the LTin
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Pahlen Norge AS Pahlen Norge AS Cha
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