Ahh ok so I'm not alone on this, I have had something similar happen in the past but never this bad. It was strange coz I wasn't exerting myself at all.
I tore a muscle in my neck about 9 months ago, and the pain was as bad as that.
I think I will rest up again tonight, just to be safe as it's still a little sore.
I think your right and it's a muscle spasm or a bad know or something, I don't think it's too serious though :)
I will be back to it tomorrow
Take it easy. You're doing calf raises for a week per Dr. @steemmatt.
Oh damn how did I miss this comment, thanks doc ;)