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Due to the difficulty of measuring forces and torques acting on a swimmer during mid-pool swimming, an inverse dynamics approach is required. Personalised body segment parameter (BSP) data enabling calculation of net forces and torques can be obtained using the elliptical zone method. The purpose of this study was to establish the reliability of estimating BSP data of swimmers by the elliptical zone method with segment outlines being traced manually on a personal computer screen. Five assessors digitised the segment landmarks and traced the body segments from front and side view digital photographs of 11 single arm amputee swimmers. Each swimmer was assessed five times by each of the five assessors. The order was fully randomised. Within assessor variability was less than 5% for the segment centre of mass position of all segments, for segment length except the neck (5.2%), and for segment mass except neck (11.9%), hands (Left: 8.1%; Right: 5.8%) and feet (Left: 7.3%; Right: 7.3%). Analysis of mean variability within and between assessors indicated that between assessor variability was generally as large or larger than within assessor variability. Consequently it is recommended that when seeking personalised BSP data to maximise the accuracy of derived kinetics and sensitivity for longitudinal and bilateral within-subject comparisons the individual should be assessed by the same assessor with mean values obtained from five repeat digitisations. This study established that using the elliptical zone method using E-Zone software is a reliable and convenient way of obtaining personalised BSP data for use in analysis of swimming.

Presently, no examination of arm stroke phases has been undertaken for swimmers with a single-arm amputation. It is likely that the roles of their affected- and unaffected-arm within the stroke cycle may differ. Understanding these would be of great practical importance. The aim of this study was to determine if the arm stroke phases used by competitive unilateral arm amputee crawl swimmers differed between their affected and unaffected sides and whether these phases altered with an increase in speed. METHODS: Thirteen (3 male & 10 female) highly-trained swimmers (age 16.9 ± 3.1 yrs) consented to participate. All were elbow level, single-arm amputees. Mean 50 m crawl best time was 32.7 ± 3.1 s. Participants completed five 25 m crawl trials, counterbalanced from slow to maximum swimming speed (SSmax). Trials were video-taped underwater from both sides using tracking camera systems. Three consecutive, non-breathing stroke cycles were analysed. Arm stroke phases for both the unaffected- and affected-arm were determined at 80%, 85%, 90%, 95% and 100% of SSmax. General linear modelling tests were used to compare the changes in arm stroke phases between the affected and unaffected arms across swimming speeds. Statistical significance was set at p < .05. RESULTS: Across swimming speeds, the affected-arm spent relatively longer (p < .05) in all arm stroke phases, with the exception of the Pull phase, compared to the unaffected-arm: Entry and Glide (38.3 ± 9.5% vs. 23.2 ± 8.0%); Pull (10.9 ± 2.8% vs. 23.1 ± 5.9%); Push (18.4 ± 6.4% vs. 13.8 ± 2.7%); Recovery (39.9 ± 3.5% vs. 35.9 ± 3.2%). With increasing speed: 1) the affected-arm’s Entry and Glide phase decreased significantly (p < .05), while the unaffected-arm’s Entry and Glide phase remained unchanged; 2) the unaffected-arm’s Pull phase decreased significantly (p < .05), while the affected-arm’s Pull phase remained unchanged; 3) both arms’ Push phase increased significantly (p < .05). DISCUSSION: With an increase in swimming speed the stroke phases of the affected and unaffected arms differed significantly. Such differences might be linked to how these swimmers organised the motor skills necessary to swim crawl. As swimming speed increased the relative durations of certain arm stroke phases changed. The single-arm amputees used a coordination strategy that asymmetrically adjusted their arm movements to maintain the stable repetition of their overall arm stroke cycle when swimming at different speeds.

Rotation about the body’s longitudinal axis in front crawl swimming or ‘bodyroll’ may serve many useful functions including: facilitating the breathing action, aiding arm recovery and reducing drag. The torque exerted by the buoyant force about the longitudinal axis, as the arm is recovered over the water, is an important mechanism for driving bodyroll. A single arm amputation may limit a swimmer’s ability to generate bodyroll. The purpose of this study was to quantify the buoyant torque experienced by single arm amputee front crawl swimmers about their longitudinal axis and its effect on their bodyroll. METHODS: The buoyant torque acting about the longitudinal axis depends on the positions of the whole body centre of mass (CM) and centre of buoyancy (CB) relative to this axis, and the magnitude of the buoyant force. These variables were calculated from body segment masses and volumes, and the position-time histories of each segment. Six female single arm (at-elbow) amputees performed nonbreathing front crawl trials at sprint pace. Trials were recorded above and below water with six video cameras. A thirteen-segment full body model of the swimmer was defined. One complete stroke cycle was digitised and 3D coordinates obtained. Body segment data were calculated from digital photographs of the participants, using the elliptical zone method. Bodyroll was described by the angular displacements of the upper trunk (shoulder roll) and lower trunk (hip roll). Buoyant torque was obtained from the cross product of the whole body CM— CB position vector and the buoyant force vector. RESULTS: Swimmers experienced significantly higher peak buoyant torques during recovery of the unaffected arm (8.1±1.4 N.m) than during recovery of the partially-amputated arm (3.5±0.9 N.m). Maximum body roll angles during the unaffected-arm recovery (shoulder: 41±8°; hip: 30±5°) were higher than those during recovery of the partially amputated arm (shoulder: 32±6°; hip: 23±6°). DISCUSSION: The buoyant torque always acted to decelerate the bodyroll from arm exit to mid-recovery and then to accelerate it from mid-recovery to arm entry. The considerable bilateral asymmetry in the buoyant torque could not account for the bodyroll patterns displayed by any of the swimmers. This indicates that the swimmers were utilising mechanisms other than the buoyant torque, such as external torques from non-propulsive fluid forces, to control their bodyroll.

Published in association with the British Association of Sport and Exercise Sciences, this is the only up-to-date, practical guide to using the range of biomechanics movement analysis machines, equipment and software available today. It includes detailed explanations of the key theory underlying biomechanics testing, along with advice concerning choice of equipment and how to use your laboratory equipment most effectively. The book covers the following important topics in detail: * motion analysis using video and on-line systems * measurement of force and pressure in the laboratory and field * measurement of power using isokinetic dynamometry * electromyography * computational simulation and modelling of human movement * research methodologies, data processing and data smoothing. Contributors include world leading researchers and pioneers such as Roger Bartlett, Carl Payton, Vasilios (Bill) Baltzopoulos, Adrian Burden, John H. Challis, and computer modelling maestro Fred Yeadon. Biomechanical Evaluation of Movement in Sport and Exercise is a must-have text for all biomechanics laboratories and students undertaking research.

The purpose of this study was to determine the effect of repeated sprint performance and fatigue on the kinematics of butterfly swimming. Six experienced national youth male butterfly swimmers undertook a maximal effort repeated sprint test set, during which swimmers were filmed with two underwater and two above water cameras (oblique plane) at 50Hz. The whole body was digitised during a full stroke cycle for each view, with the three-dimensional coordinates being obtained using a DLT algorithm. The results of this study indicate that as swimming speed decreased (i) stroke rate decreased while stroke length remained relatively constant, (ii) hand movement patterns remained similar while changes in elbow angle suggested that the effectiveness of joint flexors and extensors may have been reduced, (iii) the Upsweep, Recovery and Catch appear to the critical stroke phases when swimmers become fatigued.