The Effect of Volitional Preemptive Abdominal Contraction on Biomechanical Measures During A Front Versus Back Loaded Barbell Squat.
Joseph B McCormick, Alexander S Drusch, Darragh J Lynch and 8 others
PMID 37547830WHAT IT FOUND
Adding volitional abdominal bracing to barbell squats did not change muscle activation but slowed movement and reduced lumbar extension.
Front squats produced higher trunk muscle activity and lower hip and ankle moments than back squats, regardless of bracing.
Key findings
01Volitional preemptive abdominal contraction (VPAC) did not significantly change trunk muscle activity during either front or back squats.
02VPAC resulted in significantly decreased lumbar extension and increased time to reach peak hip and knee angles during both squat variations.
03Front squats resulted in significantly higher trunk muscle activity (internal/external obliques and iliocostalis lumborum) and lower hip and ankle moments compared to back squats.
STILL TO COME
How it was doneWhat they foundWhat it means for PTs
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What it does not show
The study used a convenience sample of only 26 healthy males, limiting generalizability to females or individuals with pathology. Participants were instructed on VPAC shortly before testing, so they may not have mastered the skill or been able to fully relax between trials. A ceiling effect in trunk muscle activation was suspected at the 75% 1RM load, meaning muscles may have already been bracing automatically regardless of VPAC instruction. Front squats were performed at a lower absolute load than back squats, which may confound direct comparisons of muscle activation and biomechanics. The findings are specific to barbell squats and may not apply to other functional lifting tasks or industrial settings.
Declared interests
One author is the co-founder of a company (TKQuant LLC), but the authors state this relationship has nothing to do with the submitted work. All other authors declared no conflicts of interest.
The easy way to misread this
Do not conclude that abdominal bracing increases trunk muscle activation; it did not. The observed changes were kinematic (slower movement, more neutral spine), likely due to the attentional demand of the task rather than increased muscular effort.