Velocity-Based Method in Free-Weight and Machine-Based Training Modalities: The Degree of Freedom Matters.

Hernández-Belmonte, A, Buendía-Romero, Á, Pallares, JG, and Martínez-Cava, A. Velocity-based method in free-weight and machine-based training modalities: the degree of freedom matters. J Strength Cond Res XX(X): 000-000, 2023-This study aimed to analyze and compare the load-velocity relationships of free-weight and machine-based modalities of 4 resistance exercises. Moreover, we examined the influence of the subject's strength level on these load-velocity relationships. Fifty men completed a loading test in the free-weight and machine-based modalities of the bench press, full squat, shoulder press, and prone bench pull exercises. General and individual relationships between relative intensity (%1RM) and velocity variables were studied through the coefficient of determination (R2) and standard error of the estimate (SEE). Moreover, the velocity attained to each %1RM was compared between both modalities. Subjects were divided into stronger and weaker to study whether the subject's strength level influences the mean test (mean propulsive velocity [MPVTest]) and 1RM (MPV1RM) velocities. For both modalities, very close relationships (R2 ≥ 0.95) and reduced estimation errors were found when velocity was analyzed as a dependent (SEE ≤ 0.086 m·s-1) and independent (SEE ≤ 5.7% 1RM) variable concerning the %1RM. Fits were found to be higher (R2 ≥ 0.995) for individual load-velocity relationships. Concerning the between-modality comparison, the velocity attained at each intensity (from 30 to 100% 1RM) was significantly faster for the free-weight variant. Finally, nonsignificant differences were found when comparing MPVTest (differences ≤ 0.02 m·s-1) and MPV1RM (differences ≤ 0.01 m·s-1) between stronger and weaker subjects. These findings prove the accuracy and stability of the velocity-based method in the free-weight and machine-based variants but highlight the need to use the load-velocity relationship (preferably the individual one) specific to each training modality.