Author(s): SAŠEK, M., CVJETICANIN, O., ŠARABON, N., Institution: UNIVERSITY OF PRIMORSKA: UNIVERZA NA PRIMORSKEM, Country: SLOVENIA, Abstract-ID: 1229

INTRODUCTION:
Resisted sprint training improves sprint acceleration performance [1,2], therefore it is commonly used as a training method for enhancing sprint speed [3]. However, the optimal magnitude of external loads for training remains debatable [4,5]. In practice various devices are employed to apply the resistance while sprinting, including sleds, motorised devices, pulley systems, or other friction-based assemblies [6]. Most devices, except from motorised and sleds, do not allow for horizontal force production assessment [7], hindering the adjustment of load towards the most optimal one [8]. Therefore, this study aimed to introduce a novel hydraulic resistance device (HRD), a cost-effective solution that enable precise application of resistance and measurement of performance during sprinting. Because the dynamics of resisted sprints with HRD remains unknown, this study assessed the differences in sprint velocity and force-velocity profiles with low, medium and hight HRD loads.
METHODS:
Participants (28) performed three 20-m resisted sprints at low (~15 N), medium (~50 N) and high (~130 N) HRD resistance loads. Magnetic encoders and pressure sensors embedded in the HRD were used to acquire instantaneous sprinting velocity and control the resistance force magnitude, respectively. Maximal sprinting velocity (Vmax) was obtained, and the decrease in sprint velocity (Vdrop) with medium and high HRD load was calculated as a percentage of low load Vmax. Furthermore, the f-v profile variables (F0, V0, Pmax, and Sfv) of resisted sprints were calculated based on the resistance force produced by the HRD and sprint acceleration at particular HRD load. The effect of HRD resistance on Vmax and the f-v profile was tested with one-way ANOVA. To distinguish between low, medium and high HRD loads, Bonferroni post-hoc test was used. The significance level was set at P<0.05.
RESULTS:
The Vmax under low HRD load ranged from a minimum of 6.07 to a maximum of 8.33 m/s. A significant effect of HRD load on Vmax were observed (F1.4,38.6 = 947, P < 0.001, partial η2 = 0.97). When adding medium and high HRD loads, Vmax decreased for 10.7±3.3% and 32.9±6.5%, respectively (p < 0.001). The HRD load had a significant impact on all f-v profile variables. Post-hoc comparisons showed a steeper Sfv at a high load compared to medium and low (-110.0 vs. -87.9 vs. 78.2 N/kg/s/m, respectively), greater F0 at high and medium load compared to low load (9.6 vs. 9.1 vs 8.5 N/kg, respectively), and greater Pmax of low and medium loads compared to high load (16.4 vs. 16.5 vs 14.8 W/kg, respectively).
CONCLUSION:
The Vdrop as a consequence of medium and high HRD loads is comparable to previously reported values in the literature [9], therefore, we encourage the utilization of hydraulic resistance for resisted sprint training purposes. Using a medium HRD load when aiming to target high power production during 20-m sprints is recommended, whereas high HRD loads are advised to increase horizontal force production capacity.