Under some circumstances, your safety may be in risk.
Q. Every running book I've read says that regular squats with a barbell are not good for distance runners. Do you think regular squats are OK for distance runners?
A. Since it activates all the muscles in the legs, including the hamstrings, butt, quads, and calf muscles, and also the lower-back muscles, the squat is a highly popular exercise. The argument against squatting for distance runners goes something like this: even when performed properly (hint - here's my video tip to perform a proper squat), a squat can stretch knee ligaments in sideways and front back directions, which can damage an already overworked knee.
Unfortunately, no studies have proven this to be true. However, from a functional standpoint, a runner rarely does a traditional two-legged squat while running. So instead, distance runners should primarily do single-legged squats in a leg strengthening program. Here's a video that shows how.