Injured

I was running late to aerobics on Monday, and when I arrived, they were finished with warm-up, and going strong with cardio. I grabbed my gear and jumped in the step routine. BIG MISTAKE. It wasn't three minutes later, a bomb went off in my right calf, and I went straight to the floor. Apparently, I "popped" a tendon. Popping a tendon HURTS. One time in high school I pulled a ham string at drill team practice, but other than that, I've never so much as strained a muscle. No broken bones, sprains, or spurs either. I'm unaccustomed to being incapacitated.
I've been laid up for two days. I don't have time for an injury. But the good news is that I'll have loads more sympathy for the master. Never again will I tell him, "Why don't you use your crutches?" or "How come you don't just hop?" when he has his prosthetic off in the evenings. Crutches are horrible awkward devices of torture, and hopping is exhausting and--in this house--dangerous.