Feasibility of the 2-point method to determine the load-velocity relationship variables during the countermovement jump exercise.

Purpose: This study aimed to examine the reliability and validity of load-velocity (L-V) relationship variables obtained through the 2-point method using different load combinations and velocity variables.
Methods: Twenty men performed 2 identical sessions consisting of 2 countermovement jumps against 4 external loads (20 kg, 40 kg, 60 kg, and 80 kg) and a heavy squat against a load linked to a mean velocity (MV) of 0.55 m/s (load _0.55 ). The L-V relationship variables (load-axis intercept (L ₀ ), velocity-axis intercept (v ₀ ), and area under the L-V relationship line (A _line )) were obtained using 3 velocity variables (MV, mean propulsive velocity (MPV), and peak velocity) by the multiple-point method including (20-40-60-80-load _0.55 ) and excluding (20-40-60-80) the heavy squat, as well as from their respective 2-point methods (20-load _0.55 and 20-80).
Results: The L-V relationship variables were obtained with an acceptable reliability (coefficient of variation (CV) ≤ 7.30%; intra-class correlation coefficient ≥ 0.63). The reliability of L ₀ and v ₀ was comparable for both methods (CV _ratio (calculated as higher value/lower value): 1.11-1.12), but the multiple-point method provided A _line with a greater reliability (CV _ratio  = 1.26). The use of a heavy squat provided the L-V relationship variables with a comparable or higher reliability than the use of a heavy countermovement jump load (CV _ratio : 1.06-1.19). The peak velocity provided the load-velocity relationship variables with the greatest reliability (CV _ratio : 1.15-1.86) followed by the MV (CV _ratio : 1.07-1.18), and finally the MPV. The 2-point methods only revealed an acceptable validity for the MV and MPV (effect size ≤ 0.19; Pearson's product-moment correlation coefficient ≥ 0.96; Lin's concordance correlation coefficient ≥ 0.94).
Conclusion: The 2-point method obtained from a heavy squat load and MV or MPV is a quick, safe, and reliable procedure to evaluate the lower-body maximal neuromuscular capacities through the L-V relationship.
Competing Interests: Competing interests The authors declare that they have no competing interests.
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