I was foolish to do this very thing occasionally back in the day... and I paid a heavy price for it to a couple years ago.
I went in and started in on some heavy deads (I lift in my home gym which is predominately freeweights) with no warmup whatsoever. I felt a slight pop, and had a small bulge in my upper abdomen which I pushed back in with just a finger poke.
the next day I realized I had pretty much gave myself a hernia. I took a lengthy break from the weight room as I didn't have health insurance at the time being self employed, eventually I went in for a CAT scan... luckily due to my avoidance of any strenuous lifting for such a long period of time, it actually healed on its own.
CAT scans aren't very fun, but when you get to see the imagery of your insides like you were sliced into 2mm increments its some fascinating shit. on a side note it was good to see that my heart and other organs were all of normal size and healthy.
bottom line, I would advise against this practice even though it is tempting when your judgement is impaired and you feel like superman.