Dose-Dependent Effects of Heel Elevation on Kinetic Chain Reconstruction and Lumbar Stress During Loaded Squatting in Men With Restricted Ankle Dorsiflexion

ABSTRACT: Cai, J, Sun, D, Li, F, Chen, D, Zhu, J, Song, Y, Fan, Y, Goda, TJ, and Gu, Y. Dose-dependent effects of heel elevation on kinetic chain reconstruction and lumbar stress during loaded squatting in men with restricted ankle dorsiflexion. J Strength Cond Res XX(X): 000-000, 2026-The aim of this study was to determine whether graded heel elevation modifies squat biomechanics, neuromuscular activity, and lumbar stress in men with restricted ankle dorsiflexion. Thirty healthy men performed loaded squats under 6 heel-elevation conditions (0, 1, 2, 3, 4, and 5 cm). Three-dimensional motion capture, force plates, and surface electromyography were used to assess lower-limb kinematics, net joint moments, center-of-pressure variables, muscle activity, and co-contraction. Finite element analysis was used to quantify peak von Mises stress in the L1-L5 segments. Discrete outcomes were analyzed using repeated-measures analysis of variance, and joint-moment waveforms were compared using one-dimensional statistical parametric mapping (SPM1D), with significance set at p ≤ 0.05. Increasing heel elevation reduced peak ankle dorsiflexion and trunk forward inclination, while increasing peak knee flexion, hip flexion, and tibial progression angle (all p < 0.001). Peak knee moment increased with heel elevation (p < 0.001), whereas ankle and hip moments were not significantly changed. SPM1D revealed prolonged increases in knee moment during the middle phase of the squat cycle. Center-of-pressure path length increased at 2-3 cm and declined at higher elevations. Selected muscle activities and co-contraction indices increased, whereas peak von Mises stress in L3-L5 decreased overall, with the greatest reduction at L4. These findings show that heel elevation produces a dose-dependent redistribution of the lower-limb-to-trunk kinetic chain. Practitioners may use heel lifts to promote deeper, more upright squats, but excessive elevation may increase knee extensor demand.