Author(s): JIMENEZ-REYES, P., GARCÍA-RAMOS, A., CROSS, M., CONCEIÇÃO, F., SAMOZINO, P., MORIN, J.B., Institution: REY JUAN CARLOS UNIVERSITY, MADRID, ESPAÑA, Country: SPAIN, Abstract-ID: 2304

INTRODUCTION:
Resisted sled sprinting (RSS) is widely used to enhance sprint acceleration and horizontal force production [1]. Current methods to individualize RSS loading typically rely on multiple-load load–velocity (L–v) profiling, which requires several resisted and unresisted maximal sprints [2,3]. While effective, this approach can be time-consuming, fatiguing, and impractical in high-performance environments. Simplified alternatives such as the 2-point method have shown validity in strength exercises, but their applicability to resisted sprinting remains unclear [4]. Therefore, this study aimed to examine and compare the concurrent validity of simplified 2-point and traditional multiple-point method to characterize individual resisted sprint load-velocity relationship and estimate maximal unloaded running velocity and maximal theoretical load.
METHODS:
Twenty-three international rugby sevens players were tested in two sessions separated by 48–72 h, performing in randomised order a multiple-load and a two-load resisted sprint protocol. The sprint L–v relationship was established using a multiple-point method (four loads corresponding to 25, 50, 75, and 100% of body mass [BM]) and a 2-point method (two loads at 25 and 75% BM). For each load, the peak velocity maintained for 2 s during maximal-effort sprinting was recorded and used to model the L–v relationship. Individual L–v relationships were obtained using full data from the multiple-point method and from both direct and indirect 2-point estimations.
RESULTS:
No significant differences were found between the multiple-point and 2-point methods for the estimation of L₀ and v₀. Trivial-to-small effect sizes (Cohen’s d ≤ 0.34), nearly perfect correlations (r ≥ 0.92), minor homoscedastic errors (r² ≤ 0.03), and no fixed or proportional bias according to ordinary least-products regression were observed between the standard method and both the direct and indirect 2-point methods. The level of agreement was consistent across participants, with low random error, indicating that the simplified 2-point method can provide comparable L–v profiling outcomes.
CONCLUSION:
In habituated athletes, the direct 2-point method is a practical tool for routinely assessing the L-v relationship during resisted sled sprinting and estimating both v0 and L0. This method offers several advantages over the standard multiple-load approach, including reduced testing time, lower fatigue, and decreased physical burden from unresisted sprints. Therefore, when appropriately implemented, the direct 2-point method can facilitate regular monitoring, estimation of maximal velocity from the L–v relationship, and individualized load prescription in applied sprint training settings.

References
1. Petrakos G, Morin JB, Egan B. Sports Med. 2016;46(3):381-400.
2. Cross MR, Samozino P, Brown SR, Morin JB. Eur J Appl Physiol. 2018;118(3):563-571.
3. Samozino P, Rabita G, Dorel S, et al. Scand J Med Sci Sport. 2016;26(6):648-658.
4. García-Ramos A. Int J Sports Physiol Perform. 2023