How tight of a degree should your knee be when lifting weights?

Normally when doing strength training, legs should be straight but not locked. When doing squats, lower yourself just below where the tops of your thighs are parallel to the floor and then raise yourself. (Never bounce at the bottom.) Also, keep your knees behind an imaginary line drawn straight up from the front of your toes. To do that, sit back when you are beginning to go down almost as if you were going to sit in a chair. Keep a similar position when doing leg presses.

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