Why Am I So Tired After Long Runs?

Man sleeping
Jose Luis Pelaez

It's normal to be a little tired after a long run. You've expended a lot of energy and put physical demands on your body. You are likely to want to take it easy the rest of the day, go to bed early, or even lie down for an afternoon nap. The day after a long run is a time for light activity and recovery. However, if you feel exhausted and your recovery seems slow, there are a few things to keep in mind.

Fueling for Your Long Runs

It can be very much an individual choice for how much and when you eat before a long run, but it is generally good not to start on empty. You want some fuel stores available for your muscles to use on the run. During a long run, be sure you are replenishing your energy stores with sports drink, gels, and other fuel as needed. Aim for 100 calories after an hour of running and then another 100 calories after every 40 to 45 minutes. You don't want to bonk or hit the dreaded "wall." This is when your body runs out of all fuel sources, leaving you with severe weakness, fatigue, and confusion.

After running, especially a long run, replenish your energy as quickly as possible. Muscles are most receptive to rebuilding glycogen (stored glucose) stores within the first 30 minutes after exercise. If you eat soon after your workout, you can minimize muscle stiffness and soreness, and help reduce your fatigue.

After your runs, consume primarily carbs, but don't ignore protein. A good rule of thumb for post-run food is a ratio of 1 gram of protein to 3 grams of carbs. Nutrition bars, such as Clif bars or Power bars, are healthy options. Other examples would be a bagel with peanut butter or a smoothie made with fruit and yogurt. Many runners like to drink chocolate milk after a long run, which also has the right carbs to protein ratio.

Also, keep track of what you're eating and make sure you're following a balanced diet throughout the week. A runner's diet should include 60 to 65 percent carbohydrates, 15 to 20 percent protein, and no more than 20 to 25 percent fat. Whole grains, lean meats, beans, legumes, and a variety of vegetables and fruits will provide your essential nutrients. However, if you still feel low energy or exhausted all the time, ask your doctor for a blood test to determine if you have low iron or another deficiency.

Hydrating for Your Long Runs

If you get dehydrated during your long run, you are likely to experience more fatigue afterward. Start off well-hydrated by drinking a large glass of water an hour before your run. Be sure you have access to water and sports drink throughout your run. The guidelines for long runs are to drink when thirsty and switch to a sports drink that replenishes electrolytes after the first 30 minutes. One tactic is to weigh yourself before and after a long run. You should have no weight loss or weight gain if you are hydrating correctly. If your urine is dark yellow after your run rather than light yellow, you aren't hydrating enough.

Be sure you are getting enough water each day. Your needs will vary depending on your climate and how much you sweat in your workouts, but 64 ounces per day one common suggestion. You should drink enough so your urine is straw-colored or very light yellow throughout the day.

Getting Enough Sleep

Sleep is part of the recovery process. It's important to rest when your body is telling you to take a nap, go to bed early, or stay in bed an extra hour. Listen to your body rather than thinking these needs are excessive. But you also need to ensure you are getting enough sleep throughout the week.

Aim for seven to eight quality hours of sleep a night—the right amount for most adults. Getting very little sleep during the week and trying to "catch up" on the weekends is not a good idea because it alters your sleep schedule. Your body is forced to adjust to these changes and, as a result, your quality of sleep is poor. Try to establish a more consistent daily sleep schedule. Starting a running morning habit may be a good way to get yourself in bed earlier most nights.

Avoid Overtraining

Running too many miles and not giving yourself any rest days will leave you feeling exhausted most of the time. Don't let your weekly mileage increase by more than 10 percent. Also, try to give yourself periodic "rest weeks" by dropping your mileage by 50 percent every four to five weeks.

A long run will result in a build-up of lactic acid and other waste products in your muscles and tissues, which causes weakness and fatigue. It takes time for your body to eliminate the waste products and repair the muscle fibers. If your hard workouts are too close together, you aren't allowing time for this recovery.

When you are training for a long-distance event such as a half-marathon or marathon, you'll be increasing the distance of your long run each week.  A training schedule is built so the total mileage per week doesn't exceed the 10 percent guideline. It also has alternating hard days, easy days, and rest days so you have recovery time.

Rest and Recovery Days

After a hard run, take a rest day. After a long run, you will need more than 24 hours to fully restore your energy reserves. You should keep any activity at an easy effort. You might want to take an easy run to shake out the stiffness, but make sure it is easy and not a training run.

Also, you should work some cross-training activities to your schedule. Doing activities other than running prevents boredom, works different muscles, and can give your running muscles and joints a break.

A Word From Verywell

Listen to your body. When you feel fatigue, it is time to take it easy. If your tiredness continues despite getting enough sleep, good nutrition, and plenty of recovery time, see your doctor for a checkup.

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