Muscle Mass and Training Status Do Not Affect the Maximum Number of Repetitions in Different Upper-Body Resistance Exercises

Background : Data investigating the factors that influence the relationship between different percentages of one repetition maximum (1RM) and the maximum number of repetitions (RM’s) performed are scarce when the movement velocity of each repetition is controlled during the RM’s test. Objective : To evaluate the RM’s performed at 60, 75, and 90% of 1RM in 4 different upper-body free weight exercises: bench press, barbell triceps extension, unilateral dumbbell elbow flexion, unilateral bent knee dumbbell row. Method : Thirty participants, 15 trained (T) and 15 untrained (UT) men, volunteered to participate in this study and attended six separate occasions, each separated by at least 48 h. In the first three sessions, familiarization and 1RM tests were evaluated. The last three sessions were designed to assess the performance of the RM’s at 60%, 75%, and 90% 1RM. The exercise order and intensities performed in each session were randomized. Muscle action velocity for each repetition was controlled by an electronic metronome. Results : There was no significant difference between T and UT in any of the exercises at a given exercise intensity. Moreover, there was no significant difference in the number of repetitions performed when exercises with different muscle mass (i.e., bench press vs. triceps extension, and dumbbell row vs. elbow flexion) at different intensities (i.e., 60%, 75%, and 90%) were compared. Conclusion : Using the same percentage of 1RM, the participants performed a similar number of repetitions in the four free weight upper-body exercises evaluated.