Perception of changes in bar velocity in resistance training: Accuracy levels within and between exercises

Velocity-based training is a method used to monitor resistance-training programs based on repetition velocities measured with tracking devices. Since velocity measuring devices can be expensive and impractical, trainee's perception of changes in velocity (PCV) may be used as a possible substitute. Here, 20 resistance-trained males first completed 1 Repetition Maximum (RM) tests in the bench-press and squat. Then, in three counterbalanced sessions, participants completed four sets of eight repetitions in both exercises using 60%1RM (two-sessions) or 70%1RM. Starting from the second repetition, participants reported their PCV of each repetition as a percentage of the first repetition. Accuracy of PCV was calculated as the difference between PCV and actual changes in velocity measured with a linear-encoder. Three key findings emerged. First, the absolute error in the bench-press and squat was ≈5.8 percentage-points in the second repetition, and increased to 13.2 and 16.7 percentage-points, respectively, by the eighth repetition. Second, participants reduced the absolute error in the second 60%1RM session compared to the first by ≈1.7 in both exercises (p ≤ 0.007). Third, participants were 4.2 times more likely to underestimate changes velocity in the squat compared to the bench-press. The gradual increments in the absolute error suggest that PCV may be better suited for sets of fewer repetitions (e.g., 4-5) and wider velocity-loss threshold ranges (e.g., 5-10%). The reduced absolute error in the second 60%1RM session suggests that PCV accuracy can be improved with practice. The systematic underestimation error in the squat suggests that a correction factor may increase PCV accuracy in this exercise.