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

<b>Background:</b> Velocity-based training (VBT) is used to estimate maximal strength and prescribe resistance-training loads, but evidence in untrained youth, especially early-adolescent females, is limited. In untrained early-adolescent females performing free-weight 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. <b>Methods:</b> Thirty-four 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. <b>Results:</b> 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; <i>p</i> > 0.35). Actual and General MVTs overestimated 1RM (+5.1 kg; <i>p</i> < 0.001), whereas an individualized Optimal MVT (~0.38 m·s^-1) removed bias (+0.6 kg; <i>p</i> = 0.52) and reduced error (<i>p</i> ≈ 0.03). <b>Conclusions:</b> 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.