Background: The relationship between the external load lifted and movement velocity can be modeled by a simple linear regression, and the variables derived from the load-velocity (L-V) relationship were recently used to estimate the maximal neuromuscular capacities during 2 variants of the back-squat exercise. Hypothesis: The L-V relationship variables will be highly reliable and will be highly associated with the traditional tests commonly used to evaluate the maximal force and power. Study Design: Twenty-four male wrestlers performed 5 testing sessions (a 1-repetition maximum [1RM] session, and 4 experimental sessions [2 with the concentric-only back-squat and 2 with the eccentric-concentric back-squat]). Each experimental session consisted of performing 3 repetitions against 5 loads (45%-55%-65%-75%-85% of the 1RM), followed by single 1RM attempts. Level of Evidence: Level 3. Methods: Individual L-V relationships were modeled from the mean velocity collected under all loading conditions from which the following 3 variables were calculated: load-axis intercept ( L₀), velocity-axis intercept ( v₀), and area under the line ( A_line = L₀· v₀/2). The back-squat 1RM strength and the maximum power determined as the apex of the power-velocity relationship ( P_max) were also determined as traditional measures of maximal force and power capacities, respectively. Results: The between-session reliability was high for the A_line (coefficient of variation [CV] range = 2.58%-4.37%; intraclass correlation coefficient [ICC] range = 0.98-0.99) and generally acceptable for L₀ and v₀ (CV range = 5.08%-9.01%; ICC range = 0.45-0.96). Regarding the concurrent validity, the correlations were very large between L₀ and the 1RM strength ( r_range = 0.87-0.88) and nearly perfect between A_line and P_max ( r = 0.98-0.99). Conclusion: The load-velocity relationship variables can be obtained with a high reliability ( L₀, v₀, and A_line) and validity ( L₀ and A_line) during the back-squat exercise. Clinical Relevance: The load-velocity relationship modeling represents a quick and simple procedure to estimate the maximal neuromuscular capacities of lower-body muscles.