Q:Why do I always want to take a nap after I run?
Pushing your body too hard without enough time in between to rest can cause extreme tiredness after a workout. Chronic soreness, irritability, lack of motivation, and nausea are also common symptoms of overtraining. It is important to vary your workouts and rest when you need to in order to avoid this. If you are doing a moderate amount of exercise (30 minutes 3-5 days per week), chances are that overtraining is not a significant factor.
Your body is about 60% water, most of which is stored in your muscles. To ensure that your muscles and other organs have enough water for optimal function, it is important to hydrate BEFORE a workout as well as during and after. Most people remember to drink during and after, but they miss the key element of PRE-HYDRATION. Drink a little bit before you leave the house and on the way to the gym to allow the water time to be absorbed into the body.
Lack of Carbohydrates
Most of Americans get an excess of carbohydrates in the form of breads, cereals, pasta, potatoes, granola bars, fruits, vegetables, etc. Lack of carbohydrates can come into play in fatigue when you are trying to keep carbohydrates low and may not have enough glucose to sustain your energy during a workout. Remember that carbohydrates are necessary for the body to function properly. That does not, however, mean that we need to run to the grocery stores and stock our pantries with granola and power bars. The natural carbohydrates in fruits and vegetables are more than enough to give your body the energy it needs to exercise at whatever intensity you desire. Consider the addition of a small amount of protein to your fruit/vegetable to keep your energy sustained throughout the workout. When eaten alone, carbohydrates can be metabolized quickly, leading to loss of energy during exercise.
Medications and Medical Conditions
Certain medical conditions like diabetes, hypoglycemia, and low thyroid and medications like ones used for depression, blood pressure, and anxiety can all interfere with energy levels in everyday activities as well as during exercise. If you have any of these conditions or take such medications, keep in mind that you may have to adjust your workout to fit your energy level or break up your exercise into smaller increments throughout the day.
Know your body. If you have accounted for all these factors (and have been cleared by a physician), this might just be the way your body responds to exertion. A large number of people have more energy when they exercise, but this is sometimes a delayed response (greater overall energy, but still worn out after a workout) while some get an immediate boost in energy. Knowing your bodys natural response to exercise can help you plan workouts that are efficient, effective, and fit into your life. Try exercising at different times of the day to see what works best for you. If you consistently want to sleep after exercise, try a workout before bed. If you feel energetic after exercise, try to fit it into your morning routine or a short workout (even a brief walk) after lunch to turn the afternoon slump into an energy boost.