Author(s): BARQUERO JIMENEZ, J., DENNIS, J., STONE, M., MIZUGUCHI, S., MONTE, A., GAHREMAN, D., DUCA, M. , Institution: EAST TENNESSEE STATE UNIVERSITY, Country: UNITED STATES, Abstract-ID: 1206

INTRODUCTION:
Block periodization sequences training phases to potentiate adaptations from strength endurance to maximal strength and power (1, 2, 3). Although widely applied in high-performance sport, empirical evidence describing the time course of neuromuscular, sprint mechanics, and morphological adaptations in track and field athletes remains limited. This study examined phase-specific adaptations across a block-periodized off-season in NCAA Division I sprinters and jumpers.
METHODS:
Eighteen NCAA Division I sprinters and jumpers completed an 11-week long intervention consisting of sequential Strength-Endurance (SE, 4 weeks), Basic Strength (BS, 4 weeks), and Strength-Power (SP, 3 weeks) blocks. Testing was performed at Baseline, post-SE, post-BS, and post-SP. Neuromuscular performance was assessed using squat jumps (SJ) and countermovement jumps (CMJ) on dual force plates (1000 Hz). Sprint performance was evaluated over 30 m with 10 m splits, and sprint mechanical variables were derived from macroscopic force-velocity profiling (4). Vastus lateralis cross-sectional area (CSA) was assessed using B-mode ultrasonography. Adaptations were analyzed using linear mixed-effects models.
RESULTS:
Morphological adaptations were phase-specific, with CSA increasing significantly after SE (F = 3.021, p = 0.042) and remaining elevated through SP. Jump performance followed a potentiated pattern: SJ height increased significantly only after SP (F = 5.233, p = 0.003), whereas CMJ height improved after SE and SP (F = 18.100, p < 0.001). Kinetically, SJ peak force increased during SE and BS (F = 35.970, p < 0.001), while SJ peak power improved after BS (F = 24.397, p < 0.001). In the CMJ, peak propulsive power increased significantly after BS (F = 4.884, p = 0.005), while peak force decreased following SE (F = 12.89, p < 0.001). Sprint performance improvements were confined to early acceleration, with faster 0-10 m times observed after BS (F = 5.745, p < 0.001) and maintained through SP, with no changes in later splits. These changes were driven by increases in force-related mechanical variables rather than velocity. However, the ratio of horizontal-to-resultant force decreased across the later blocks (F = 7.159, p < 0.001), indicating reduced horizontal force application efficiency despite greater force production capability.
CONCLUSION:
Block-periodized off-season training elicited phase-specific adaptations consistent with the phase potentiation model. SE training induced hypertrophy, BS enhanced force production and early acceleration, and SP training facilitated the expression of explosive performance. Acceleration improvements were primarily mediated by enhanced force capacity rather than velocity, while horizontal force application efficiency declined across the off-season.
[1] Stone 2021/ [2] DeWeese 2015/ [3] Suchomel 2018 / [4] Morin 2016