Why Am I So Tired After Long Runs?

Trail runner breathing hard after run on mountain

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It's normal to be 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 fit in an afternoon nap. The next day is a time for light activity and recovery.


One goal of long slow distance running is to train your muscles to spend hours running and being on your feet. If you are training for a distance event, you need to learn to run through fatigue and practice proper pacing, as well as hydrating and fueling on the run

This takes time to learn.

However, if you're so exhausted after a long run that you can't function at all, make some changes to both your preparation and recovery strategies.

Fuel Up First

How much and when to eat before a long run is an individual choice, but it is generally not good to start on empty. You need some fuel stores for your muscles to use on the run. During a long run, be sure you are replenishing your energy stores with sports drinks, gels, and other fuel as needed.

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.

Aim to consume 100 calories after an hour of running and then another 100 calories every 40 to 45 minutes.

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

Consume primarily carbs, but don't ignore protein. Many runners like to drink chocolate milk after a long run because it has a good ratio of carbs to protein.

Eat Well Every Day

It's also important to follow a balanced diet throughout the week (not just on long-run days). A runner's diet should include 60% to 65% carbohydrates, 15 to 20 percent protein, and no more than 20% to 25% fat. Whole grains, lean meats, beans, legumes, and a variety of vegetables and fruits will provide your essential nutrients.

If you're eating and sleeping well, but you still feel exhausted all the time, ask your doctor for a blood test to determine if you have low iron or another nutritional deficiency.

Keep Hydrating

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 guideline for long runs is 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.

Make H2O a Habit

Be sure you are getting enough water each day (long run or not). Your needs will vary depending on your climate and how much you sweat in your workouts, but 64 ounces per day is a common suggestion. You should drink enough so your urine is straw-colored or very light yellow throughout the day.

Nap as Needed

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 after a long run. Listen to your body rather than thinking these needs are excessive. Look at your post-run activity as part of your training, and try to block off time to nap or just rest your legs.

Remember that sleep is how your body recovers from intense exercise. While you're sleeping, your taxed and tired muscles are getting rebuilt so they can run again (and run longer, and run faster).

Get Enough Sleep Regularly

That's also why you need to ensure you are getting enough sleep throughout the week. Aim for at least seven to eight good-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 forces your body to adjust to an altered sleep schedule. As a result, your quality of sleep can be poor.

Starting a habit of running in the morning may be a good way to get yourself in bed earlier most nights.

Avoid Overtraining

As you're planning your running calendar, avoid the "too"s: Too much running, running too often, and running too fast. If you're finding it hard to recover after a long run, you may be going too far or at a pace that's too fast for this distance.

Never increase your weekly mileage by more than 10%.

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.

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

Split Up a Long Run

Sometimes, you may find that even though your training schedule calls for it, you can't complete your long run in one session. For instance:

  • You don't have an uninterrupted chunk of 2 or more hours in your schedule.
  • It's very hot and humid outside and running for an extended time could lead to dehydration or heat stroke.
  • You are healing from or at risk of an injury and should not run 3 or more hours without a break.

By running some of your mileage in the morning and the rest later on during the day, your body is getting most of the same physical endurance training benefits of a continuous long run (since you're not sleeping or allowing enough time for significant recovery in between your two runs). Your legs are fatigued already and your energy stores are somewhat depleted, so you do get some cumulative effect.

It's easier mentally to run 10 miles in the morning and 8 miles at night, rather than 18 miles all at once—which is why you don't want to split your run every week. But it definitely beats the alternative of skipping your long run altogether.

Rest and Recovery Days

A long run results 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.

It takes more than 24 hours to fully restore your energy reserves after a long run.

Always take a rest day after a hard run. Keep any activity at an easy effort level. You might want to take a slow, gentle run to shake out the stiffness, but make sure it is easy and not a training run. Give yourself periodic "rest weeks" by dropping your mileage by 50% every four to five weeks. Listen to your body. When you feel fatigued, it is time to take it easy.

2 Sources
Verywell Fit uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Rodriguez NR, Di Marco NM, Langley S. American College of Sports Medicine position stand. Nutrition and athletic performanceMed Sci Sports Exerc. 2009;41(3):709-31. doi:10.1249/MSS.0b013e31890eb86.

  2. Kerksick CM, Arent S, Schoenfeld BJ, et al. International society of sports nutrition position stand: Nutrient timingJ Int Soc Sports Nutr. 2017;14:33. doi:10.1186/s12970-017-0189-4.

Additional Reading

By Christine Luff, ACE-CPT
Christine Many Luff is a personal trainer, fitness nutrition specialist, and Road Runners Club of America Certified Coach.