Force-Velocity Profiles and Optimal Loads During Sled Towing in Rugby Players

Earnshaw, Kristy-Anne
Earnshaw, Kristy
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Master of Sport and Exercise
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Auckland University of Technology

Recent research has focussed on improving and developing on-field sport-specific measurement technologies and methodologies to enhance sprint performance. As a result of this, resisted overground sprinting has gained popularity recently as both a training method and sprint assessment method. Researchers and strength and conditioning coaches have paid particular interest to the ability to profile athletes force-velocity (F-V) capabilities using sled resisted overground sprinting. This information can be used to determine the optimal training load for maximal power output. However, this has only been investigated in a limited number of sporting cohorts, primarily recreational and sprint-trained athletes. The aim of this thesis was two-fold, 1) to evaluate current sled tow research focussing specifically on the technologies and methodologies currently used to assess sprint performance in field-based sports, and 2) to provide initial benchmark information for strength and conditioning coaches on positional demands for semi-elite male rugby union players using the newly introduced instrumented sled as the sprint assessment tool. Chapter 2 presents a narrative review of the current sled tow literature in court and field-sport athletes and highlights the need for research that streamlines methodological approaches. The review draws attention to the need to provide new and updated technology that can accurately assess sprint performance variables within a range of sporting cohorts. Consequently, chapter 3 presents a relatively new sprint assessment tool being an instrumented sled and which was used to determine the F-V and power-velocity (P-V) relationships within male rugby union players. The accuracy of the instrumented sled to measure sprint performance variables was determined by fitting the F-V relationship with linear regressions and the P-V relationship fitted with polynomial quadratic regressions (second-order), with both relationships being near perfect (F-V: R2= 0.983, P-V: R2= 0.986). Subsequently, chapter 4 compared sprint performance variables measured from the instrumented sled by position (forwards vs. backs) within semi-elite male rugby players. The research found there to be significant positional differences between the forwards and backs for F0 (P≤ 0.02, ES= -0.75, %difference= 12.4%) and Pmax values (P≤ 0.01, ES= 0.82, %difference= 8%) with forwards displaying more force dominant profiles than backs. These differences were likely influenced by physical attributes and positional demands. Relative to body weight the optimal loads on average were 55.87%BW for the forwards and 61.1%BW (ES=0.37) for the backs. This result is important to note as it highlights how individualised optimal loading is to not only each sporting cohort but also to the positional groups within each sport. Given the promising results of these early studies using the instrumented sled, strength and conditioning coaches and researchers should consider the use of such technology as an accurate sprint performance assessment and training tool.

Sled Tow , Force-Velocity Profile , Resisted Sprinting , Instrumented Sled , Acceleration , Optimal Loads
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