Why do squats make me so out of breath and get my heart rate up?

I run a lot. I can run for miles, it's my favorite workout. I recently started doing more strength training though... I do like 15 squats and get out of breath and need to take a couple seconds break?
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+1 y
How long is it okay to take breaks in between sets? A lot of the time I'll do a set every commercial break if I'm watching TV or something. But I don't know if that will do anything. I want a toned butt! I have a pancake ass
Why do squats make me so out of breath and get my heart rate up?
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