Exercise is perhaps the single best activity you can do for your health. Not only will you feel better in the short-term, but also exercise also reduces your lifetime risk of heart attack, stroke and even cancer. Although exercise can be exhausting, it should not cause an overall decrease in sleepiness. In fact, exercise may increase your energy level.
Exercise and Fatigue
Immediately after exercising, your muscles may feel sore. Particularly if you're just beginning an exercise routine, the first few weeks of exercise can be exhausting, and you may feel sleepy either immediately after exercise or a few hours later. This exhaustion should fade as your body adjusts to regular exercise, and after a few weeks, exercise shouldn't directly make you sleepy. If you find that you continue to be sleepy after several weeks of exercise, consult your doctor.
Exercise and Energy
Exercise is much more likely to boost energy levels rather than lead to sleepiness. Regular physical activity boosts blood oxygen levels, which can help you feel more energetic throughout the day, not just after exercise. Exercise also releases endorphins. These feel-good chemicals can increase your energy level, and many people find that they have a substantial boost in energy immediately after a workout. Over the long-term, regular workouts improve cardiovascular fitness. This can make daily routines less stressful for your body, also increasing your overall energy level.
Daily activity is strongly correlated with falling asleep more quickly at night. Although exercise shouldn't make you sleepy immediately, it can help your body better regulate its internal clock. A 2009 study published in the "Archives of Disease in Childhood" found that the amount of time it took children to fall asleep at night was inversely correlated with their activity levels during the day. Children who were more active fell asleep more quickly and, on average, each hour of sedentary time added three minutes to the amount of time it took to fall asleep.
Mood and Sleep
Exercise can dramatically improve your mood both by releasing endorphins and improving overall health and body image. Improved mood can directly affect sleep. First, decreased anxiety and depression may make it easier to fall asleep at night. Second, an improved mood can boost your energy and productivity levels during the day, reducing daytime drowsiness.