Effects of Different Loading Types on the Validity and Magnitude of Force-Velocity Relationship Parameters.

Background: Force-velocity (F-V) relationship models gained popularity as a tool for muscle mechanical assessment. However, it is not clear whether the validity of the F-V relationship parameters (maximal theoretical force [ F ₀], velocity [ V ₀] and power [ P _max]) is affected using different load types: gravitational (W, rubber bands pulling the barbell downward), inertial (I, rubber bands pulling the barbell, which is equalized to the weight of the added plates upward), and combined (W + I, weight of the plates). Hypothesis: Load type would affect both the magnitude and validity of F-V relationship parameters. The highest magnitude and validity was expected for F ₀ using a W, for V ₀ using an I, and for P _max using a W + I load. Study Design: Cross-sectional. Level of Evidence: Level 3. Methods: A total of 13 resistance-trained men (body mass, 87.7 ± 11.2 kg and body height, 183.9 ± 6.4 cm) performed bench press (BP) throws (BPTs) using 3 types of loads against 30 to 80 kg. The validity of F-V relationship parameters was explored with respect to the tests used traditionally for force (maximal voluntary contraction and 1-repetition maximum [1RM]), velocity (maximal velocity achieved during almost unloaded tasks), and power (BPT against the 50%1RM and medicine ball throws) assessment. Results: The W + I loading promoted the highest values of F ₀ and P _max, while the highest magnitude of V ₀ was promoted by the I loading. The validity was acceptable for F ₀ obtained using the 3 loading conditions with respect to the BP 1RM (r range, 0.30-0.83), and V ₀ obtained using the I loading with respect to the stick throw (r = 0.54). Conclusion: The magnitude of the F-V relationship parameters is affected by load type, but their validity with respect to standardized tests is comparable, with the exception of the higher validity of V ₀ when obtained using the I loading. Clinical Relevance: Any load type can be used for assessing F ₀, while I load should be selected when assessing V ₀. [ABSTRACT FROM AUTHOR]