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Resistance Training/Periodization

(12) ELECTROMYOGRAPHIC CHARACTERISTICS OF INTENTIONALLY SLOW, VOLITIONAL, AND MAXIMAL VELOCITY REPETITIONS OF THE BENCH PRESS EXERCISE

Thursday, July 13, 2023
2:00 PM – 3:30 PM East Coast USA Time
Location: Milano III-IV
Abstract Details: Repetition velocity is a training variable that can be modified to influence the resistance training stimulus. Previous work has demonstrated the influence velocity has on lifting kinetics and kinematics, with intentionally slow velocities yielding reduced force and power outputs. As early adaptations are often attributed to neural aspects, understanding the influence velocity has on electromyographic (EMG) characteristics is warranted.

Purpose: The purpose of this study was to compare the EMG characteristics of the bench press under varying resistance training velocities.

Methods: Recreationally trained males (X±SD; n = 14, age = 24.0±3.9 yrs, height = 175.7±8.2 cm, mass = 89.6±13.4 kg, 1RM = 111.4±20.7 kg) participated in this study. A minimum of 48 hours after 1RM testing, participants completed a bench press exercise protocol consisting of 3 repetitions each separated by 2 minutes rest at four different concentric durations with 50% 1RM loads: 3-second (3SEC), 1-second (1SEC), self-selected (SELF), and maximal velocity (MAXV). Surface EMG electrodes were used to measure EMG amplitude during all conditions. Electrodes were attached to the pectoralis major, anterior deltoid, and triceps brachii muscles. EMG amplitudes are expressed as relative percentages of the amplitude achieved for each muscle during MAXV. A 3x4 (muscle x condition) repeated-measures ANOVA analyzed the muscle by condition interaction for peak and mean EMG data. Significant two-way interactions were followed up with 1x4 repeated-measures ANOVAs for each muscle to note differences between conditions. For significant main effects and two-way interaction, partial eta squared effect sizes (ηp2) are reported. For post-hoc comparisons, Hedges’ g effect sizes are reported.

Results: For mean concentric EMG amplitude, a main effect for condition was noted (p < 0.001, ηp2 = 0.730). The main effect for muscle was non-significant (p = 0.827, ηp2 = 0.013). Pairwise comparisons for mean concentric EMG amplitude between conditions when collapsing across muscles showed that 3SEC (p = < 0.001-0.001, g = 1.290-4.061) and 1SEC (p = < 0.001-0.008, g = 0.998-2.698) were lower than MAXV and SELF. MAXV and SELF were not different (p = 1.000, g = 0.108). A significant two-way interaction between muscle and condition was noted for peak concentric EMG amplitude (p = 0.002, ηp2 = 0.217). For pectoralis major, 3SEC was significantly lower than MAXV (p = 0.010, g = 0.973) and SELF (p = 0.008, g = 0.997). For triceps, MAXV was significantly greater than 1SEC (p = 0.006, g = 1.037) and 3SEC (p < 0.001, g = 1.420). For the anterior deltoid, greater EMG amplitudes were noted for MAXV when compared to 1SEC (p = 0.011, g = 0.968) and 3SEC (p < 0.001, g = 1.346), with higher SELF when compared to 3SEC (p = 0.006, g = 1.036). 

Conclusion: Despite constant load between conditions, significant differences in EMG amplitudes were noted, with intentionally slow velocities resulting in lower EMG amplitudes. As intensity may influence motor unit recruitment, intentionally slow velocities yield different neuromuscular characteristics, which may influence acute performance and adaptation. PRACTICAL APPLICATION: As velocity appears to influence neuromuscular performance, coaches and practitioners must consider training velocity when force-velocity adaptations are desired. Intentionally slow velocities yield different recruitment strategies, impacting long-term adaptation.

Acknowledgements: None