The Magic School Bus - Works Out - Ep. 35

At this year's Teacherathalon, Ms. Frizzle is competing against Mr. Sinew (Dan Marino), the gym teacher with giant muscles. Janet shows up again and supports him. The class is convinced that there is no way Ms. Frizzle can beat someone who can destroy shirts simply by flexing his muscles. Ralphie wants to know what lungs have to do with how your muscles work, so they go on a field trip inside Ms. Frizzle herself.