I don't know if this qualifies as a strained chest muscles, but I did suffer a pretty serious chest injury while I was working out a few years back.
I was benching and I had a pretty serious amount of weight on the bar. I had a spotter and was expecting to get five reps in before my muscles gave out. Well, I got to the fourth rep, my spotter got distracted by a pretty girl and I ended up dropping the bar onto my chest. I broke three ribs in the process. I am completely healed up now and have no lasting pain, but I never expected to leave the gym with broken bones.