A two-year fitness program assisted middle-aged couch potatoes in becoming fit and reversing the consequences of years of sitting. Exercise is also considered effective in treating chronic fatigue syndrome, depression, anxiety, post-traumatic stress disorder (PTSD), and sleep disorders such as insomnia. Exercise is physical activity that makes you breathe hard and gets your heart pumping. It can be as simple as walking up a flight of stairs or throwing a ball around with your friends. Moderate exercise is anything that makes you sweat for 30 minutes without stopping. It could be a run up a hill or taking the stairs instead of the elevator. Vigorous exercise is anything that makes you sweat for 30 minutes and cause some pain such as playing soccer or tennis. It can also be a bike ride or a weight-lifting session. The amount of exercise you need depends on your age, gender, and how much energy you use every day. If you are relatively inactive, it's best to start out by exercising for 30 minutes several times per week. As you become more active, you can increase the time you spend exercising each week. However, don't overdo it; stay within your body's limits. The most important thing is that you feel excited about your progress.