Author(s): BERTOCHI, G., TASINAFO, M., PUGGINA, E., Institution: UNIVERSITY OF SÃO PAULO, Country: BRAZIL, Abstract-ID: 936

INTRODUCTION:
Improving sprint performance has been a primary objective across different sports contexts, especially in track and field. Due to the limited transfer from strength training to sprint performance, resisted sprint techniques, such as limb loading, have been an alternative. However, the acute performance and kinematic impacts of 5% of body mass (BM) limb loading in track and field athletes during the acceleration and maximum velocity sprint phases remain unclear. Thus, the present study aimed to examine performance and kinematic changes across the acceleration and maximum velocity phases of sprint using a 5% BM load applied to the thigh.
METHODS:
Twelve experienced track and field athletes (age: 22.3±3.5 y; height: 1.7±0.1 m; BM: 66.8±13.3 kg; training experience: 5.0±3.8 y; best reported 100-m 11.9±0.8 s) participated in this study. Participants performed three 100 m sprints with 10 minutes of rest on two separate days: unloaded and with a 5% BM thigh load (TL). The TL scheme involved loads ranging from 175 to 200g, attached via velcro to each participant's shorts, 2/3 anteriorly and 1/3 posteriorly. A sagittal-plane video recorded with a high-speed camera set to 2704x1520 pixels and 120 frames quantified sprint performance and kinematics. Four pairs of tripods spaced 10 m apart were used to evaluate the 50-m and 10-m split times. Kinematic analysis evaluated ground contact and flight times, as well as step frequency and length. Dependent t-test examined the differences between conditions (p≥0.05) with Cohen's d effect size.
RESULTS:
Significantly higher 50-m sprint time (3.77±1.94 %; ES: -1.96 [large]) and lower mean 50-m velocity (-3.60±1.83 %; ES: 1.95 [large]) were observed for the TL compared to the unload condition. Each 10-m split time (2.86 to 4.69 %; ES: -0.98 to -2.69 [large]) was significantly higher in the TL compared to the unload condition. A significant decrease in all split times for mean velocity (-2.70 to -4.45 %: 0.95 to 2.78 [large]) was observed for the TL compared to the unload condition. Ground contact time significantly increased in the acceleration and maximum velocity phases (5.92 to 6.54 %; ES: -1.47 to -1.51 [large]) in the TL compared to the unloaded condition. A significant decrease in step frequency during the acceleration and maximum velocity phases (-1.61 to -2.01 %; ES: -0.88 to 1.08 [large]) was observed in the TL condition compared with the unloaded condition.
CONCLUSION:
Sprinting with 5% BM TL significantly overloaded sprinting. Sprint time and ground contact time increased significantly, while mean velocity and step frequency decreased significantly in the TL condition. Coaches and sports practitioners should be cautious when using 5% BM TL if the aim is to develop sprint performance with minimal influence on sprint technique. Longitudinal studies are required to investigate the long-term adaptations of TL sprinting.