Author(s): VOLK, N.R., FERRAUTI, A., Institution: RUHR UNIVERSITÄT BOCHUM, Country: GERMANY, Abstract-ID: 2307

INTRODUCTION:
Optimizing sprint performance is crucial in many sports (e.g., football) (1). In this regard, resisted and assisted sprints are commonly used training methods (2). There is still insufficient evidence regarding the efficiency of interventions for individuals with different preconditions and their adaptation to training (1). Therefore, the study aims to evaluate the effects of resisted and assisted sprint training on two groups of subjects with contrasting force-velocity profiles.
METHODS:
After initial pre-testing (PRE), 15 male students volunteered for a 6-week training intervention (two sessions per week) followed by two post-tests (POST) separated by one week. The intervention included either heavy-resisted sprints (HRS; n=7) or assisted sprints (ASS; n=8). PRE and POST included two all-out 30m outdoor sprints and a load-velocity profile (LVP) using three resisted sprint conditions (10, 20, 30% body weight). Subjects were categorized into a force-dominant (FD) or a velocity-dominant (VD) type based on their force-velocity profile (F-v) according to the median of an unpublished male reference sample (n=47). Subjects were then randomly advised to either HRS or ASS. Prior to each training session, a free 30m sprint was conducted to set the subsequent training intensity under consideration of LVP. The HRS group targeted a 40-60% velocity loss over 10-20m. The ASS group aimed for a 5-10% velocity increase over 25-35m. All measurements and training loadings were conducted using a motorized device (333 Hz). Descriptive and individual analyses were used to evaluate the changes in split times (5m, 30m) and F-v measurements (F0, v0).
RESULTS:
Small improvements between PRE and POST were shown in HRS (5m: -0.08±0.15s, d: -0.54±1.00; 30m: -0.07±0.16s, d: -0.39±0.87; F0: 0.28±0.64 N/kg), while small changes in ASS were only found for v0 (0.20±0.22m/s, d: 0.50±0.59). Overall, beneficial adaptations were less in the ASS for short-distance measurements at POST but more profound for longer-distance measurements. Regarding the FD and VD typology, subgroups demonstrated inconsistent changes independent of the training group.
CONCLUSION:
Individual effects after a 6-week training intervention of heavy resisted or assisted sprint training are not straightforward. The HRS intervention tends to lead to more beneficial adaptations towards acceleration-dominant measurements, while over-speed training seems to improve only speed-dominant measurements. However, this dataset does not provide a definitive conclusion depending on the initial slope and training group. There are small indications that the acceleration of subjects with a flatter F-v slope (VD) might benefit from HRS. An extension of the dataset is in process.

(1) Lahti et al. 2020, Sports, 8(5), 74. doi: 10.3390/sports8050074
(2) Cahill et al. 2019, Sports, 7(5), doi: 119. 10.3390/sports7050119