Sex-related Differences In Neuromuscular Efficiency During The Bench Press At 70 And 90% Of 1 Rm

Abstract

Neuromuscular efficiency (NE) is the ability of the nervous system to properly recruit the correct muscles to produce force, reduce force as well as dynamically stabilize the body’s structure in all three planes of motion (NASM). Although NE is closely allied with fiber recruitment and rate coding, hormonal differences between sexes may influence NE, the number of repetitions performed at a given % 1RM and the resistance training (RT) response. A 1RM requires the individual to use both neurological and muscular ability in order to recruit many motor units into contraction. Often males recruit more motor units than females during a 1RM which provides a greater absolute working load. PURPOSE: The purpose of this study was to examine the number of repetitions males and females can achieve during the bench press using 70% and 90% of 1RM. METHODS: 20 recreational athletes (10♀) with a minimum of one year of RT experience (age 24.3 ± 5.0 yrs, ht 170.4 ± 8.9 cm, body mass 73.9 ± 16.5 kg) performed a familiarization trial with submaximal and 1RM bench press lifts. Trials at 70% and 90% 1RM were randomly assigned, terminated at momentary muscular fatigue (MMF), and conducted with a minimum of 48 hrs between trials. All lifts were conducted at a standard movement cadence of 3-1-3 sec (concentric-pause- eccentric muscle contraction). The number of repetitions (R) performed at each percentage of their 1RM were recorded. RESULTS: Statistical analysis by an independent T-test revealed a significant difference (P<.05) of R at 70% (10.7 ± 2.1 vs 6.8 ± 1.1) and 90% (4.3 ± 1.2 vs 2.9 ± 0.6) for females and males, respectively. A Pearson correlation also revealed a significant correlation between R at 70% and 90% trials. CONCLUSION: The ability of females to perform a greater number of repetitions prior to MMF at both 70% and 90% of their 1RM, when compared to their male counterparts, may indicate that the traditional percentage based resistance training exercise prescriptions may be inappropriate for women. Females may require resistance training at a higher percentage of their previously determined 1RM in order to achieve MMF in a given repetition range.