Lumpyoatmeal saidI bought one at the recommendation of my physical therapist. She didn't recommend it for what was ailing me (a very slight tenderness in the right of my hip) but because I told her I ran. I didn't see any benefit from it and it seemed like a lot of (as in too much) work for apparently not doing anything, so I stopped using it. I was already stretching after my runs. I'm only doing 45 minutes of cardio 3 times a week (15 mins stationary bicycling, 30 mins running) so I'm obviously not pounding my body.
Even healthy runners should do some kind of SMR stretching prior to static stretching. Your body is constantly creating a fibrous layer of connective tissue called fascia. The stress from running can prevent the body from forming fascia in the correct pattern leading to decreased range of motion and increasing the chance of injury. SMR prevents that.
That's the theory and it sounds logical. But I'd love to see some research that proves it.
Most recently "Foam Rolling and Static Stretching on Passive Hip Flexion Range of Motion" in the Journal of Sport Rehabilitation in January 2014
A quote from one link about the article says "They therefore concluded that foam rolling can lead to the same significant improvements in hip flexion range of motion as passive static stretching."http://tinyurl.com/lwwnkpp
But to continue being quarrelsome and nit-picking, notice that they say it increases the range of motion, not that it reduces injury. That's the sticky point for me. People are assuming that increasing the range of motion decreases injury, which as I said sounds logical but I don't think has been proven with research.
I didn't realize until a year or so ago that there's a controversy about stretching; some runners think it can lead to injuries and that you're better off not stretching. That surprised me. My theory is that it's better to stretch after you run, when your muscles are thoroughly warmed up, and to be very careful to not overstretch.