Acta Gymnica e2026.010 | DOI: 10.5507/ag.2026.010

Muscle activation in squat jumps with barbell vs. hex-bar: Effects of load magnitude

Tinkara Dolanc, Nana Mihelčič, Domen Tominec, Darjan Spudić

Faculty of Sport, University of Ljubljana, Ljubljana, Slovenia

Background: The use of hex-bar equipment has recently gained attention in strength and conditioning. Vertical jump mechanics are fundamental to many sport-specific tasks, including sprinting, change-of-direction, and acceleration. Understanding how load magnitude and the choice of hex-bar versus traditional barbell influence neuromuscular responses can inform targeted training interventions designed to enhance performance and reduce injury risk.

Objective: This study examined lower-limb muscle activation during squat jumps (SJs) across different jump time intervals and external loads, using traditional barbell and hex-bar.

Methods: Fifteen resistance-trained men (age 25.0 ± 3.0 years) performed SJs at 100%, 120%, 140%, and 160% of their body mass. Electromyographic activity (EMG) from eight lower-limb and back muscles, as well as vertical ground reaction force, was recorded. EMG amplitudes and average ground reaction force were analysed across six time-normalized intervals (five during push-off, one pre-initiation).

Results: Repeated-measures analysis of variance revealed that muscle activation responses were muscle- and load-specific. Hamstring activation remained unchanged across all conditions, whereas erector spinae, gluteus maximus, soleus, rectus femoris, and vastus lateralis generally showed greater activation with heavier loads, with ~50% of comparisons reaching statistical significance. Equipment-specific differences were most evident in rectus femoris activation, which was consistently lower during hex-bar SJs from initiation through mid-push-off. Participants jumped higher with the hex-bar, and jump height declined with increasing load.

Conclusions: These findings indicate that external load systematically alters muscle activation strategies, resulting in corresponding changes in force production, while the effects of equipment are more subtle and muscle-specific.

Keywords: activation patterns, muscle coordination, ballistic, power training, performance

Received: October 28, 2025; Revised: July 27, 2026; Accepted: August 25, 2026; Published online: September 16, 2026  Show citation