The addition of very light loads into the routine testing of the bench press increases the reliability of the force-velocity relationship

Background: The aim of this study was to examine whether the addition of very light loads for modeling the force-velocity (F-V) relationship during the bench press (BP) exercise can confirm its experimental linearity as well as to increase the reliability and concurrent validity of the F-V relationship parameters (maximum force (F₀), maximum velocity (V₀), F-V slope, and maximum power (P_max)). Method: The F-V relationship of 19 healthy men were determined using three different methods: (I) 6-loads free method: six loads performed during the traditional free-weight BP exercise (≈ 1-8-29-39-49-59 kg), (II) 4-loads free method: four loads performed during the traditional free-weight BP exercise (≈ 29-39-49-59 kg), and (III) 4-loads Smith method: four loads performed during the ballistic bench press throw exercise in a Smith machine (≈ 29-39-49-59 kg). Results: The linearity of the F-V relationship was very high and comparable for the three F-V methods (p = 0.204; median Pearson's correlation coefficient (r) = 0.99). The three methods were ranked from the most to the least reliable as follows: 6-loads free (coefficient of variation (CV) range = 3.6-6.7%) > 4-loads Smith (CV range = 4.6-12.4%) > 4-loads free (CV range = 3.8-14.5%). The higher reliability of the 6-loads free method was especially pronounced for F-V slope (CV_ratio 1.85) and V₀ (CV_ratio 1.49) parameters, while the lowest difference in reliability was observed for F₀ (CV_ratio 1.27). The 6-loads free and 4-loads free methods showed a very high concurrent validity respect to the 4-loads Smith method for F₀ and P_max (r 0.89), a moderate validity for the F-V slope (r = 0.66-0.82), and a low validity for V₀ (r 0.37). Discussion: The routine testing of the F-V relationship of upper-body muscles through the BP exercise should include trials with very light loading conditions to enhance the reliability of the F-V relationship.