Neuromuscular Adaptations, Bilateral Asymmetry, and Sprint Mechanical Efficiency Following Velocity-Based Resistance Training in Track and Field Sprinters

الملخص

Velocity-based training (VBT) provides precise autoregulation of neuromuscular stress by monitoring bar execution speed during resistance exercise. This study evaluated the chronic effects of an eight-week VBT intervention versus traditional percentage-based training (PBT) on lower-limb bilateral mechanical asymmetry, neuromuscular rate of force development (RFD), and linear sprint kinematics in competitive sprinters. Twenty-two male track and field sprinters (age: 21.2 ± 1.5 years, body mass: 74.8 ± 4.9 kg, 100-meter personal best: 10.82 ± 0.24 s) were randomly allocated into either a VBT group (n = 11, velocity loss threshold capped strictly at 10%) or a PBT group (n = 11, fixed loading at 75% to 85% of 1RM with predetermined sets to failure). Lower-body inter-limb asymmetry was evaluated using dual force plate countermovement jumps (CMJ), while maximum strength was determined via isometric mid-thigh pull (IMTP). Kinematic sprint profiling across 10-meter, 30-meter, and 60-meter intervals was recorded using synchronized timing radar. The VBT cohort demonstrated significant reductions in lower-limb peak force asymmetry (from 11.4 ± 2.1% down to 5.2 ± 1.2%, p < 0.01), whereas the PBT cohort exhibited no statistically significant changes in inter-limb symmetry. Early-phase RFD (0–100 ms) increased by 18.6% in the VBT group compared to 7.4% in the PBT group (p < 0.01). Furthermore, VBT produced superior improvements in 30-meter acceleration times (3.88 ± 0.04 s vs. 3.96 ± 0.05 s, p < 0.05) and maximum running velocity. Autoregulating training volume via low velocity-loss cutoffs attenuates inter-limb functional deficits and optimizes rapid force generation essential for elite sprinting mechanics.