I see this all the time, and I must admit I was guilty as well my first few years training of doing this.
It’s very simple.
Don’t Squat In Running Shoes
Running shoes are meant for running, not squatting. Squat shoes are meant for squatting.
Investing in a quality set of squat shoes is an investment in your training.
Why Shouldn’t You Squat In Runners?
Well there are a few reasons.
1. The sole of a running shoe has padding and a shock absorber generally. This is designed to absorb impact. You don’t want this when squatting.
2. A padded heel. Very similar to above the padded heel in a runner will cause you to lose strength and power when squatting.
3. Stability. A running shoe has a bit of give when going side to side. A squat shoe does not.
If you are serious about lifting a set of squat shoes for squatting is essential. Deadlift in flats like chuck taylors or wrestling shoes or even barefoot, but when it comes to squatting grab a set of squat shoes and don’t squat in running shoes.
EDITED NOTE : Something I have noticed is that some people squat better in flats. They move better and squat better in flat shoes like Chucks, flats or even barefoot. From what I have seen it might be about 10% of people squat better in flats.
Don’t rule out trying barefoot versus and elevated heel to see what one works best for you.