Yeah, I can. The difference is that "physical activity" can mean anything, just walking around the job shop would do. Exercise, if done in sufficient quantity, hurts or exhausts. When you can't do it anymore, you've had "exercise" and enough of it. I obviously didn't watch the video. "Physical activity" will seem like enough for a while, as your fitness gradually decreases, but then all of a sudden you just can't run 2 miles anymore. Then you're screwed, got to build back all that fitness which is not nearly as much fun as staying fit.