In Core Training, "Bracing" or "Hollowing"?
One of the oldest debates in core training is between "hollowing" (drawing the belly in, isolating the transversus abdominis) and "bracing" (tightening the entire circumference of the abdomen). Both have their advocates. As a coach, the useful question isn't "which is absolutely correct?" — it's "in which situation will I use which?"
What does the science say?
Tayashiki and colleagues (2016) showed that 8 weeks of abdominal bracing training significantly increased trunk flexion/extension and hip extension strength, as well as maximal lifting power; intra-abdominal pressure (IAP) rose. So bracing is the foundation for stabilizing the spine during heavy lifts.
Maeo and colleagues (2013) found that bracing produced the highest activation for the transversus abdominis and internal oblique, but remained lower than the sit-up for the rectus abdominis and lower than the back extension for the back muscles. So bracing is a "stabilization" tool; it's not a "muscle-building" exercise on its own.
The most practical finding: the cue is stronger than the equipment
Bressel and colleagues' (2009) study is perhaps the most valuable for coaches. Giving a verbal co-activation instruction ("brace your belly") during the squat produced 39–167% higher abdominal muscle (rectus abdominis, external oblique, TA/internal oblique) activation than using an unstable surface or adding heavier load.
This is a very practical message: instead of putting the client on a Bosu ball or balance board, giving the right verbal cue recruits the core more. Not equipment, but directing attention does the job.
Practical rules for the coach
- Under heavy bench, squat, deadlift → bracing. Tighten the entire circumference of the abdomen as if wearing a thick belt; when needed, increase IAP with the Valsalva maneuver.
- In rehabilitation and low-load stabilization work → hollowing may be more suitable for TA isolation.
- Classic movements for muscle-building/strength: sit-up, plank, cable woodchop, ab wheel. Bracing comes in alongside these, not in their place, as a daily 5–10 minute habit.
- Invest in the verbal cue: clear cues like "brace your belly, hold your breath, pull your ribs down" are more effective than most equipment tricks.
In short: bracing and hollowing aren't rivals but tools for different jobs. Heavy load = bracing, control/rehab = hollowing. And your most powerful tool is often not in your pocket but in your mouth — the right cue.