Lol you think sitting for long periods is bad, you should research the mortality rates of marathon athletes. Your ten times more likely to die from a cardiac related incident if you exercise for more than 3 hours at a time.
What to take from information like sitting is bad and running marathons will kill you? Try to not sit on your ass all day, move around every 30 minutes and don't elevate your heart rate for hours at a time, it's an organic organ, not a machine part, it will break. Health and longevity never come from the extremes in life, they always come from behavior that's in the middle, moderation is the key to everything. (Health wise, not good advice for someone looking to win a gold medal in something)