Jordi Gillet from Barcelona in Spain asked on the StrongLifts Facebook page...
I’ve a question regarding abs.
I started StrongLifts 5x5 a few months ago and already squatting 240lb. I’ve always had a very flat stomach but now it looks as if my abs were starting to grow outwards. If I stand with my abs relaxed my belly looks bigger and sticks out more than before.
I don’t know if the problem is for following the recommendation of taking a breath and pushing your abs out when squatting, but if I look at pictures of most powerlifters I really don’t want to end up with their big bellies. I know it’s not a problem of fat because I measure it with a caliper and it hasn’t changed.
Can this be a problem of technique or something else?
It's more like a natural reaction to gaining strength on your Squats. Everybody knows that muscle size is directly related to strength gains. You've boosted your Squat to 240lb in only a few months of StrongLifts 5x5, so it's normal that you have gained muscle everywhere, including ab muscles.
The fact is that you won't keep that skinny, girly, brad-pitt-fight-club-waist if you Squat and Deadlift heavy. You will NOT develop a huge belly like many of those +300lb powerlifters have unless you let yourself become fat (just look at lighter powerlifters, they don't have huge bellies), but you will get a "weightlifter gut".
As an example, look at the before/after pictures of StrongLifts Member Ray (23y, USA, page 104 inside the 5x5 report). The middle picture is after 6 months of low calorie dieting, cardio and split routines - from fat to skinny. The right picture is after 7 months of StrongLifts 5x5, when he was Deadlifting 350lb...
Everyone will agree that Ray looks better with his weightlifter gut - it just looks stronger and more manly. Deadlifting 350lb clearly didn't make him develop a huge belly and this is proof that heavy lifting increasing waist size is a myth. Quite the opposite, plenty of StrongLifts Members have lost waist size, always while boosting their strength, and often while even gaining weight.
If your gut is really sticking out, and it's not fat, then you should look at your posture. Sitting a lot behind a computer like I do will tighten your hip flexors which will then pull your pelvis forward and make your gut and butt stick out. Some arching in your lower back is normal, but excess - hyperlordosis - isn't. Add that it not only looks bad, but can also cause lower back pain.
Picture above of StrongLifts Member "IloveSquats" shows how he eliminated his protruding gut in only 3 weeks by simply stretching his hip flexors 3x/day. Not only did people compliment him on his better posture, they also said he looked taller (no photoshop in the right picture, but he did admit he sucked his gut in - still, look at his shoulders and lower back, there's an obvious improvement).
Don't waste your time with stomach vacuums before looking at your posture. If you do daily lunge stretches for your hip flexors and shoulder dislocations for your upper-back, your protruding gut should be gone within 21 days. Meanwhile keep Squatting heavy and pushing your abs out to keep your lower back safe. As long as you eat healthy, you won't get a huge belly.