It happened to my Dad last January, and me yesterday. We pulled our boob muscle, a.k.a. pectoral or pectoralis major which majorly sucks. My dad thought he was having a heart attack when he had his, now I know what it feels like, and it's awful. Why is this blog worthy? Because of the nature in which this injury occurred, reaching behind us to attend to Brooks while in the car.
Unfortunately this job (nor my father's as grand-parent) comes with workman's comp or hazard pay. We're going to have to remember this when it's time to renegotiate our contracts.