How does one build up stamina for exercising?

I used to be able to play basketball or baseball for 2-3 hours without needing any much of a break except water here and there. I stopped playing all sports for about a year and I was wondering how could one regain this stamina or energy. I am usually out of breathe after 20-30minutes of playing.

How does one build up stamina for exercising?
You just need to increase your time level of exercise a little at a time. Set a goal of 30 minutes of activity and increase it by 5 minutes each day, or couple of days, depending on your preference and comfort level. Also, make sure that you are drinking lots of water before, during, and after exercise. Water gives you energy and keeps you hydrated enough to build up your stamina. Be sure you're eating healthy outside of your exercise activity - if you load up on carbs, your energy will be good for about 20-30 minutes, but then you'll most likely feel a decrease in energy/stamina. You need to supplement your body with proteins prior to exercise, and in your daily diet. Good luck to you, I'm sure you'll get back into it in no time! :)
Reply:Try exercising alittle bit more each time you exercise and learn to breathe properly
Reply:red bull with vodka..........than c the result
Reply:Sports requires bursts of energy...what you need to do is increase your aerobic exercises like walking, running, biking...work on getting your heartrate up and keep it up for 20 - 30 minutes. You'll need to push yourself so when you're walking...walk for 10 minutes and then run for as long as you can and then walk 10 minutes....run for as long as you can until the running and walking are of equal time or the running outlasts the walking. If you're indoors on a treadmill make yourself go uphill a little and keep increasing the speed....you'll get there. Oh, be sure to eat good healthy foods and make sure you are getting enough iron in your food.
Reply:eat a powerbar, stretch, hit something and get mad at it ( it works )