How do you build up stamina and endurance?

I see some people being able to run for 40 minutes non stop or do 20 laps in the pool while after 10 minutes or 1 lap, im exhausted. how do i build up the ability to maintain and do cardio for a long time? i dont smoke

How do you build up stamina and endurance?
There is only one answer. Push harder. Those guys you see doing more than you have been doing it longer and constantly push themselves to get better.
Reply:Years ago, I went through "basic training" for the U.S. Army; they build you up gradually over time %26amp; push you to do more %26amp; more until your stamina %26amp; endurance are built up---took me about 8 weeks. Cardio (jogging/running), push-ups, sit-ups...
Reply:Do suicides and other things. Do you go to a high school or middle school? Ask your coaches there to write you an endurance workout. Preferably a soccer, football, or basketball coach. If you would like me to write you one [I'm a football player], just send me an email.
Reply:dude...did you ever hear the saying "Practice makes perfect keep running every day everyday aim HIGHER until your pleased...work out dont eat junkfood.
Reply:You just slowly build up. Say you can run for a lap and then you're exhausted. Push yourself to run a lap and a half, then walk. Or run 5 minutes, and then walk 5 for a week alternating that for 30 minutes. The next week, run 6, walk 4, and so on. You just have to push yourself further little by little and before you know it you'll be able to go just as long.