yeah, the burn while running hurts, but it's a good burn and when you take a shower afterwards and relax, it feels awesome. i think swimming has helped me run with longer longevity as you control your breathing in both running and swimming. i've been learning the proper swimming techniques and can do the flip at each end of the pool pretty consistently. whenever i go to the gym, i do at least twenty laps, but four continously back to back for right now as i'm trying to open my lungs to longer breathing (it's hard). hopefully, one day i can run a marathon (good for you :xyxthumbs ), but i would have no one to do it with as all my friends are lazy LOL...