Quick Answer. In an officially-sanctioned MLB baseball game, there are 9 innings. If the home team is ahead in the top of the ninth and earns 3 outs, the game ends at 8 1/2 innings. If the game is tied after the away team earns 3 outs in the bottom of the ninth, the game goes into extra innings. Keep Learning.
When you exercise, the muscles you use require more energy. When exercise can be sustained, this demand is met primarily by aerobic means. Aerobic energy production in muscles results in increased gas exchange at the lungs, because more oxygen is taken in and more carbon dioxide is released.
Your heart rate increases when you exercise. Photo Credit Jupiterimages/Stockbyte/Getty Images. Your heart rate increases when you exercise, because you are working harder. How much your heart rate increases depends on the intensity of your exercise and how fit you are. Exercise experts differ on how high your heart rate should be during exercise, but they agree that it needs to be substantially higher than your resting heart rate to improve your cardiovascular fitness.