This really saved my butt last week when I developed that very painful muscle knot in my left calf. I used this a few times a day for several days, and it really worked. No issues on my Monday morning easy run. I've had some hamstring soreness too and this worked like a charm on that. If you've never used a foam roller before (whether you are a runner or not!) Here is a link to some exercises for some common issues. From here on out I plan to use it before and after runs and experiment a little. There are more inexpensive foam rollers (think large noodles!) - but I like this one for the different areas that it has. Using each area has a different 'feel' to it and it is simple to try each area till you hit one that works. It's a simple investment that pays for itself in one session - have you seen what massage therapists charge?
Not a plug for this one - but it's called The Grid if you simply have to Keep Up With Perry and his toys...lol
