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Brendan Burkett, Rebecca Mellifont, and Bruce Mason

This study compared the components of the 15-m swimming start for 20 international male Olympic and Paralympic swimmers. The time, distance, and velocity components for freestyle swimming were measured. There were significantly (p < .05) different absolute and relative swim start measures among the swimming groups. Using stepwise regression three variables significantly influenced the start to 15-m time: (i) underwater velocity, (ii) free swim velocity, and (iii) whether the swimmer had cerebral palsy. This new knowledge provides useful information for swimmers and coaches on which components to prioritize, along with the practical applications of improving the streamline position to increase underwater velocity and to ensure that the transition from underwater to surface breakout occurs at the optimal time for maximum free swim velocity.

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Danielle P. Formosa, Mark Gregory Leigh Sayers, and Brendan Burkett

This study explored and quantified gender differences in passive drag and instantaneous net drag force profile for elite backstroke swimmers (FINA points 938 ± 71). Nine female and ten male backstroke swimmers completed eight maximum speed trials. During the passive drag condition participants were towed at the speed achieved within the maximum effort backstroke swimming trials, while holding a supine stationary streamline position. The remaining trials, swimmers performed their natural swimming stroke, while attached to an assisted towing device. Male participant’s passive (P < .001) and mean net drag force (P < .001) were significantly higher compared with female participants. In addition, there were no significant differences by gender between either the minimum or maximum net drag forces produced during the left and right arm strokes. Instantaneous net drag force profiles demonstrated differences within and between individuals and genders. The swimmers who recorded the fastest speed also recorded the smallest difference in net drag force fluctuations. The instantaneous net drag force profile within elite backstroke swimming provides further insight into stroke technique of this sport.

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Andrew A. Dingley, David B. Pyne, and Brendan Burkett

Disabilities in Paralympic swimming could impact a swimmer’s ability to execute an effective swim-start. We examined how swim-start performance differed between severity and type of physical disability. Swim-starts were measured in 55 elite Paralympic swimmers from eight different Paralympic classes; S14, S13, S10-S6, S3 grouped as no- (classes S13 & S14), low- (S9 & S10), mid- (S7 & S8) or high- (≤ S6) severity of physical disability and also by type of physical disability (upper, lower, and palsy) to provide meaningful comparisons. The swimmer’s competitive level was determined by the international point score (IPS). Swimmers with no physical disability were significantly faster in most swim-start phases compared with those with physical disabilities, as were swimmers with low-severity disabilities compared with the mid- and high-severity groups. Block velocity was highly negatively correlated (r = –0.57 to –0.86) with 15-m swimming time for all groups except high-severity disabilities. Free-swim velocity is a priority area for improving swim-starts for swimmers regardless of disability, given large correlations between this measure and IPS. Swimmers with lower body or high-severity disabilities spent a smaller percentage of time overall in the underwater phase. Assessment of four specific phases of the swim-start highlight distinctive priorities for coaches working with Paralympic swimmers in an applied biomechanical manner.

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Danielle P. Formosa, Huub M. Toussaint, Bruce R. Mason, and Brendan Burkett

The measurement of active drag in swimming is a biomechanical challenge. This research compared two systems: (i) measuring active drag (MAD) and (ii) assisted towing method (ATM). Nine intermediate-level swimmers (19.7 ± 4.4 years) completed front crawl trials with both systems during one session. The mean (95% confidence interval) active drag for the two systems, at the same maximum speed of 1.68 m/s (1.40–1.87 m/s), was significantly different (p = .002) with a 55% variation in magnitude. The mean active drag was 82.3 N (74.0–90.6 N) for the MAD system and 148.3 N (127.5–169.1 N) for the ATM system. These differences were attributed to variations in swimming style within each measurement system. The inability to measure the early catch phase and kick, along with the fixed length and depth hand place requirement within the MAD system generated a different swimming technique, when compared with the more natural free swimming ATM protocol. A benefit of the MAD system was the measurement of active drag at various speeds. Conversely, the fixed towing speed of the ATM system allowed a natural self-selected arm stroke (plus kick) and the generation of an instantaneous force-time profile.

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Brendan Burkett, James Smeathers, and Timothy M. Barker

For amputees to perform an everyday task, or to participate in physical exercise, it is crucial that they have an appropriately designed and functional prosthesis. Past studies of transfemoral amputee gait have identified several limitations in the performance of amputees and in their prosthesis when compared with able-bodied walking, such as asymmetrical gait, slower walking speed, and higher energy demands. In particular the different inertial characteristics of the prosthesis relative to the sound limb results in a longer swing time for the prosthesis. The aim of this study was to determine whether this longer swing time could be addressed by modifying the alignment of the prosthesis. The following hypothesis was tested: Can the inertial characteristics of the prosthesis be improved by lowering the prosthetic knee joint, thereby producing a faster swing time? To test this hypothesis, a simple 2-D mathematical model was developed to simulate the swing-phase motion of the prosthetic leg. The model applies forward dynamics to the measured hip moment of the amputee in conjunction with the inertial characteristics of prosthetic components to predict the swing-phase motion. To evaluate the model and measure any change in prosthetic function, we conducted a kinematic analysis on four Paralympic runners as they ran. When evaluated, there was no significant difference (p > 0.05) between predicted and measured swing time. Of particular interest was how swing time was affected by changes in the position of the prosthetic knee axis. The model suggested that lowering the axis of the prosthetic knee could reduce the longer swing time. This hypothesis was confirmed when tested on the amputee runners.