ECSS Paris 2023: OP-AP22
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.
Read CV Matic SašekECSS Paris 2023: OP-AP22
INTRODUCTION: Rate of Force development (RFD) calculated at 50 and 100 ms represents the capacity to quickly produce force starting from a relaxed state during isometric contractions. The theoretical maximal velocity obtained from force-velocity (FV) relationship (V0) represents the capacity to produce force at high velocity during dynamic contractions. While these two capacities are intuitively close, their association has not been studied so far. We thus investigated the role of RFD and maximal voluntary force (MVF) on the theoretical maximal velocity (V0) and force (F0) of the knee extensors. METHODS: Single-leg knee extensors were tested under isometric and dynamic conditions in 44 young adults (15 females). Participants performed two 5-s maximal isometric contractions to calculate MVF and 10 isometric burst-like contractions to compute RFD at 50, 100, and 150 ms and at peak. Then, a set of incremental-load knee extension maximal efforts were performed on a modified knee-extension isoinertial ergometer. Force and velocity were continuously measured and averaged over 80-to-140° knee angles to determine individual hyperbolic FV relationships. RESULTS: FV relationships were well fitted by hyperbolic regression (r² from 0.983 to 0.993). Stepwise linear regression showed that isometric RFDpeak normalized to MVF was the main determinant of V0 (R2 = 0.157, P = 0.006) while MVF was the main determinant of F0 (R2 = 0.362, P < 0.001). Correlation analysis showed that RFD at 50ms (R = 0.418, P = 0.003) and RFD at 100 ms (R = 0.313, P = 0.028) correlated with V0, while RFD 150 ms correlate with F0 (R = 0.583, P < 0.001). The curvature of the FV relationship did not correlate with any RFD or MVF indexes. CONCLUSION: When obtained from averaged values over knee extension, V0 (and not F0) is partially explained by muscle contraction quickness (i.e.“explosive” force capacity). So, the capacity to produce force at high velocity partly depends on the capacity to rise quickly the force in the early phase of the contraction, suggesting that some underlying determinants of RFD would also affect V0.
Read CV gennaro bocciaECSS Paris 2023: OP-AP22
INTRODUCTION: The force-velocity profile (FVP) has shown a relationship with swimming performance (1). However, only 38% of French trainers evaluate strength and speed parameters for some exercises, possibly due to accessibility problems (especially due to price) to modern evaluation devices (2). Recent research has shown a relationship with sprint performance of the Bosco FVP, which is a simplified method that is easy to access and perform (3). Therefore, the objective of the study is to analyze the relationship of Boscos FVP with swimming performance, specifically surface and underwat METHODS: Seventeen junior swimmers performed both swimming and jumping tests. Swimming test consists of six 25 m maximal sprints from a push start in surface (front-crawl) and underwater (undulatory) conditions with three minutes rest between repetitions and conditions (in random order). Jumping test consists of CMJ and a CMJ50 (CMJ with external loads equivalent to 50% of the swimmers´ bodyweight). The best of three attemps was selected for each jump. FVP50 was calculated using Bosco´s Index (FVP50 = CMJ50/CMJ*100). RESULTS: Underwater condition showed higher mean 25 m times (16.96 ± 0.74 s vs 14.00 ± 0.86 s; p < 0.05) and fatigue index (4.50 ± 2.25 % vs 1.92 ± 0.90 %; p < 0.05). Surface swimming mean 25 m times showed very large (r = - 0.73, p < 0.05) and large (r = - 0.63, p < 0.05) relationship with CMJ (32.55 ± 5.04 cm) and CMJ50 (16.81 ± 3.12 cm) performance, respectively. Whereas underwater mean 25 m times only showed large (r = - 0.51, p < 0.05) relationship with CMJ performance. However, Bosco´s FVP50 (51.41 ± 3.64 %) only showed large relationship (r = -0.58; p < 0.05) with underwater swimming fatigue index. CONCLUSION: This study highlighted that underwater swimming may require higher explosive strength (CMJ) to improve mean 25 m times, but higher Bosco´s FVP50 (strength profile) to improve fatigue index, as has been observed in field hockey players (3). However, surface swimming may require higher CMJ and CMJ50 to improve mean 25 m times, not finding a relationship with the fatigue index because swimmers in this condition maintained better performance (possibly related to the free breathing). (1) Raineteau Y, Pla R, Bideau B, Bideau N and Nicolas G (2024) From dry-land to the water: training and testing practices of strength and conditioning coaches in high level French sprint swimmers. Front. Sports Act. Living 5:1338856. doi: 10.3389/fspor.2023.1338856 (2) Chalkiadakis, I.; Arsoniadis, G.G.; Toubekis, A.G. Dry-Land Force–Velocity, Power–Velocity, and Swimming-Specific Force Relation to Single and Repeated Sprint Swimming Performance. J. Funct. Morphol. Kinesiol. 2023, 8, 120. https://doi.org/10.3390/jfmk8030120 (3) González-Frutos, P.; Aguilar-Navarro, M.; Morencos, E.; Mallo, J.; Veiga, S. Relationships between Strength and Step Frequency with Fatigue Index in Repeated Sprint Ability. Int. J. Environ. Res. Public Health 2022, 19, 196. https://doi.org/10.3390/ijerph19010196 The present project was funded within Project PID2021-124392NA-I00 by MCIN/AEI/10.13039/501100011033 / FEDER, UE.
Read CV PABLO GONZALEZ FRUTOSECSS Paris 2023: OP-AP22