Load–Velocity Relationship and 1RM Estimation of the Free-Weight Squat in Untrained Early-Adolescent Females

Abstract

Background: Velocity-based training (VBT) is used to estimate maximal strength and prescribe resistance-training loads, but evidence in untrained youth, especially earlyadolescent females, is limited. In untrained early-adolescent females performing freeweight back squats, (1) the load–velocity relationship (LVR) is comparable to adult samples, albeit with greater between-subject variability, and (2) one-repetition maximum (1RM) estimates are affected by the minimum velocity threshold (MVT) anchor. Methods: Thirtyfour untrained females (10–14 years) completed two progressive loading tests followed by actual 1RM attempts. Mean propulsive velocity (MPV) was recorded to model LVRs. Three MVTs were considered: (a) Actual (from Test 1), (b) General (0.30 m·s−1), and (c) Optimal (individualized to minimize prediction error in Test 1). LVR-based 1RM estimates from Multi-point and Two-point approaches were generated in Test 2 using each MVT and compared with the actual 1RM. Results: MPV decreased near-linearly with load (median R2 ≈ 0.996), from 1.00 ± 0.19 m·s−1 at ~40%1RM to 0.30 ± 0.05 m·s−1 at 100%1RM. Across MVTs, Two- and Multi-point models showed similar 1RM accuracy (≤~0.7% difference; p > 0.35). Actual and General MVTs overestimated 1RM (+5.1 kg; p < 0.001), whereas an individualized Optimal MVT (~0.38 m·s−1) removed bias (+0.6 kg; p = 0.52) and reduced error (p ≈ 0.03). Conclusions: In untrained early-adolescent females, the back-squat LVR is highly linear, and 1RM estimation accuracy hinges on the MVT anchor. A streamlined Two-point LVR paired with an individualized Optimal MVT provides an efficient, accurate workflow for youth strength assessment.This project has been supported by the University of Granada, Convocatoria de Proyectos de Investigación UGR/Ciudad Autónoma de Melilla 2024 (MEL-08-UGR24) and the Unit of Research Excellence of the University of Granada, Melilla Campus, UECUMel (UCE-PP2024-02). ISA was supported by the Research Initiation Grant for Undergraduate Students, University of Granada–Banco Santander (P5A2024-81)