presented for application in sled-resisted sprinting. Chapter 4 implements ..... Custom built LabVIEW program for application of exponential decay, and analysis ...
FORCE-VELOCITY PROFILING IN SLED-RESISTED SPRINT RUNNING: DETERMINING THE OPTIMAL CONDITIONS FOR MAXIMIZING POWER
Matthew R. Cross MSpEx
A thesis submitted to Auckland University of Technology in fulfilment of the requirements for the degree of Master of Sport and Exercise
2016 School of Sport and Recreation
I
ABSTRACT The measurement of power-velocity and force-velocity relationships offers valuable insight into athletic capabilities. The qualities underlying maximum power (i.e. optimal loading conditions) are of particular interest in individualized training prescription and the enhanced development of explosive performance. While research has examined these themes using cycle ergometers and specialized treadmills, the conditions for optimal loading during over-ground sprint running have not been quantified. This thesis aimed to assess whether force-velocitypower relationships and optimal loading conditions could be profiled using a sled-resisted multiple-trial method overground, if these characteristics differentiate between recreational athletes and highly-trained sprinters, and whether conditions for optimal loading could be determined from a single sprint. Consequently, this required understanding of the friction characteristics underlying sled-resisted sprint kinetics. Chapter 3 presents a method of assessing these characteristics by dragging an instrumented sled at varying velocities and masses to find the conversion of normal force to friction force (coefficient of friction). Methods were reliable (intraclass correlation [ICC]>0.99; coefficient of variation [CV]5%. Inter-test reliability of each variable was quantified by the coefficient of variation (CV in %), intra-class correlation (ICC), and the standardized change in the mean (ES; using threshold values described) between the two testing occasions (Hopkins, 2000).
Results Tables 6 and 7 display the descriptive and between-groups comparative statistics for Fv and Pv relationships, respectively. Values of !, , &, , -, , '()* , '()* 2, d23 , !789 , &789 and -789 78
are presented in respect to the relationship from which they were determined. Where possible, values were also expressed as relative to BM. Table 8 presents test-retest reliability. For all cases in both athlete groups, Fv relationships were well fitted by linear regressions (R2 ranging from 0.994 to 0.999 for sprinters and from 0.995 to 0.999 for mixed sport athletes, all P69-96% BM). In any case, sled training should factor as part of a periodized holistic program including varying degrees of technical, unloaded, resisted and assisted sprint work and general conditioning practices. Practically, concerns of technical alterations resultant of optimally loaded sled training could be mitigated by intelligent programming, where emphasis is placed 86
on multiple capacities in the effort of producing a well-rounded program targeting multiple factors of sprinting performance. The method used to quantify mechanical capabilities intrinsically shapes the interpretation of output variables. The current work uses methods from early sprint cycling studies (Vandewalle, Peres, Heller, et al., 1987), with optimal loading conditions computed at the instance of -3 months pre-testing), and familiar with the testing procedures. Athletes were allowed to wear whatever footwear they generally perform maximal sprinting efforts in, resulting in sprinters wearing spikes and recreational athletes wearing standard athletic footwear. Following a detailed warm-up protocol, athletes performed one unloaded sprint followed by 5 or 6 sprints of towing a sled, loaded with a selection of masses, on a Mondo athletics track. The testing was preceded, and each following trial interceded, with 5 min passive rest. Equipment To provide resistance, athletes were harnessed (0.34 kg; XLR8, Model: SA1PM, Wellington, NZ; attachment point mid-low back via a 3.3 m non-elastic nylon tether) to a heavy duty sprint sled (5.64 kg; GetStrength, Model: HT 50 mm Sled, Auckland, NZ) loaded with a selection of calibrated powerlifting plates (Model: PL Comp Discs, Eleiko Sport, Halmstad, SWE). Sprinting performance was measured by a sports radar gun (Model: Stalker ATS II, Applied Concepts, Dallas, TX, USA), attached to a tripod at 5 m at a height of 1 m, collecting outward bound information at 46.9 Hz. Velocity-time data were collected using the manufacturer supplied software. Loading selection and sprint distance A maximum of seven loading protocols were prescribed to provide a sufficient span of stimuli to promote peak power production (unloaded, 20, 40, 60, 80, 100 and 120% of BM). 94
Following an unloaded sprint, loading was increased until greater than a 50% decrement in unloaded -
