Ask most people to tighten their core and they will suck their stomach in. Under heavy load, that is the opposite of what we want. A strong, stable trunk comes from breathing into it and bracing around that breath.
Learn the 360-degree breath
Lie on your back with your knees bent. Place your hands around your lower ribs, thumbs towards your back. Inhale slowly through your nose and try to feel your ribs and belly expand in every direction: forwards, sideways and into the floor. Your chest and shoulders should stay relatively quiet.
Add the brace
Once you can breathe 360 degrees, take that breath in and gently tighten the muscles around your waist, as if preparing for someone to poke you in the stomach. You should feel firm all the way around, without holding your breath painfully or turning red.
Applying it to a lift
- Set up in your starting position.
- Breathe in through the nose, into your belly and sides.
- Brace around the breath.
- Move through the hardest part of the rep while keeping the brace.
- Exhale at the top or once you are past the sticking point, then reset for the next rep.
Match the brace to the load
A light set of goblet squats needs only a gentle brace and normal breathing. A near-maximal deadlift needs a much stronger brace. Learning to scale the effort is part of the skill.
A note of caution
Briefly holding your breath under heavy load raises pressure in the body. If you have high blood pressure, a heart condition, are pregnant or have any other medical concern, speak with your doctor and use lighter loads with continuous breathing.
Practise the 360-degree breath during your warm-up. Over time it becomes automatic, and your lifts will feel noticeably more solid.