Impact of resistance training status on trunk muscle activation in a fatiguing set of heavy back squats

Abstract

Purpose In this study we measured neural activation (EMG) in four trunk stabilizer muscles and vastus lateralis (VL) in trained and novice participants during a set of squat repetitions to volitional fatigue at 85% 1RM. Methods Forty males were recruited into two groups, novice (NG: n = 21) and experienced (EG: n = 19), according to relative squat 1RM. Participants were tested twice to: (1) determine squat 1RM, and (2) complete a single set of repetitions to volitional fatigue at 85% 1RM. Relative squat 1RM; NG < 140% body mass, EG > 160% body mass. Neuromuscular activation was measured by EMG for the following: rectus abdominus (RA), external oblique (EO), lumbar sacral erector spinae (LSES), upper lumbar erector spinae (ULES) and VL in eccentric and concentric phase. Completed repetitions, RPE and EMG in repetition 1 and at 20, 40, 60, 80 and 100% of completed repetitions were analysed. Results No group differences were found between number repetitions completed and RPE in repetitions to volitional fatigue at 85% 1RM. Neuromuscular activation increased significantly in all muscle groups in eccentric and concentric phase apart from RA in the eccentric phase. Trunk neuromuscular activation was higher in NG compared to EG and this was significant in EO, LSES and ULES in eccentric phase and LSES in the concentric phase. VL activation increased in both phases with no group differences. Conclusion Trunk neuromuscular activation increases in a fatiguing set of heavy squats regardless of training status. Increased back squat strength through training results in lower neuromuscular activation despite greater absolute external squat loads.

Nuances of the Valsalva manoeuvre and bracing with regard to resistance training performance and its effects on the pelvic floor

“…Both a greater external load and a higher number of repetitions result in increases in IAP (Saldaña García et al 2020). This creates more demand on the muscles of the trunk and greater fatigue (Clark et al 2021). The core musculature is often conceptualized as a canister where the co-contraction of each of the "sides" is responsible for transfer of force.…”

“…This changes in relation to the movement being performed, the position of the trunk and the degree of spinal movement (Hamlyn et al 2007). However, to date, most of the electromyographic data on RT and the VM have not been used to evaluate the contribution of the PFMs (Hamlyn et al 2007;Clark et al 2021). Although insights can potentially be extrapolated on the contributions of the core canister to functional performance, more research is needed to clarify role of the pelvic floor.…”