Sex Differences In Velocity Metrics Across Various Repetitions In Reserve During The Barbell Bench Press

Repetitions in reserve (RIR) and velocity-based training (VBT) are popularly used to auto regulate intensity for exercise programming. Currently, velocity drop offs of 20-40% are commonly found throughout the literature, but it remains unclear how such velocity drop offs relate to RIR. PURPOSE: Due to previously established sex differences in relative barbell velocity, the purpose of this study was to evaluate the relationship between sex and relative average concentric velocity (ACV) drop off at 0-3 RIR during a barbell bench press workout. METHODS: Barbell bench press 1RM was assessed in 24 resistance trained (6.0 ± 3.9 yrs) males (n = 12; 24.1 ± 6.1 yrs) and females (n = 12; 22.5 ± 5.5 yrs) followed by a single set to volitional fatigue using 80% of the established 1RM (RTF). A linear transducer assessed ACV for each repetition throughout RTF. Percent velocity drop-off (%DO) was calculated for failure (0RIR), 1 RIR (1RIR), 2 RIR (2RIR), and 3 RIR (3RIR) using the following formula ((X repetition ACV - 1st Repetition ACV)/1st Repetition ACV). A Sex × RIR%DO repeated measures ANOVA was used to determine if sex differences were apparent. Significance was accepted at p ≤ .05. RESULTS: A main effect of RIR%DO was noted (p < .001). However, no Sex × RIR%DO interactions (p = .484) or main effects of sex (p = .312) were seen. All proximities to failure were significantly different from one other (3RIR: -14.7 ± 18.2%, 2RIR: -26 ± 16.3%, 1RIR: -38.2 ± 20.8%, 0RIR: -54.1 ± 13.3%; ps < .008). However, this was not found to be impacted by sex. CONCLUSIONS: Our data suggests that velocity decreases significantly the closer to failure a repetition is performed regardless of sex. These results leave us to conclude that at a moderate load, in a laboratory setting, there are no appreciable differences in barbell velocity at 0-3 RIR between sexes. Thus, if VBT is being used in an attempt to objectively auto regulate training, %DO does not need to be adjusted due to sex.