I just started today. My sons challenged me to a mini triathlon in April, 200 yard swim, 5 mile bike ride, and 2 mile run. They are 14 year old twins who play freshman football, I'm a 40 year old over weight former athlete back in the day but 300+ lbs today. I made it through day 1, but it took everything I had. Those last 10 seconds of the jog are the longest 10 seconds of my life it seems.