Coaches thrive on feedback. We want to know how you felt on the run, how hard or easy the effort was, if there were any hints of pain. Are you sleeping well? Eating enough? There are a lot of warning signs that athletes may be unaware of, but coaches and sports dietitians are always on the lookout for an athlete at risk of overtraining or under-fueling.

When the body is overstressed, we lose fitness instead of gaining it. When an athlete isn’t eating enough to support their training, it’s a form of stress and can impact endurance, strength, and speed gains. Both overtraining or underfueling put an athlete at risk for injury and impaired health.

First, runners need to understand stress.

Training is essentially a dose-response stress test. A little stress can go a long way for fitness gains. Acute stress doses from speed work, long runs, and an increase in training volume can result in faster paces and improved endurance. These acute stresses, or training blocks, can also increase your body’s energy (food) needs. This stress must be balanced with recovery in the form of easy workouts, rest days, adequate sleep, and sufficient energy (food and nutrient) intake.

Especially when training for a lofty goal or a new personal challenge (e.g. your first marathon or a 5K PR), it’s tempting to ignore a nagging pain or a bad night’s sleep in order to complete a workout as planned or hit a specific pace. But too much stress results in overtraining and high risk of injury. Chronic lifestyle stress may influence your training as well (e.g. work, travel, emotional or relationship stress, illness, etc.) Ultrarunner and running coach Krissy Moehl asks that her athletes track hours of sleep per night, and include detailed notes with each workout. Both provide data that could point to overtraining. “If someone mentions heavy legs, or difficulty getting up to work out, it may be a sign they’re not recovering well,” she notes. “I adjust their schedule to reduce the stress load a bit.”

The following are symptoms of chronically high stress levels:

  • Trouble sleeping (falling asleep or sleeping through the night)
  • Chronic fatigue
  • Irritability
  • Headaches
  • Upset stomach
  • Muscle tension or pain
  • Lack of motivation
  • Anxiety or depression

A workout journal with consistent notes on energy and effort can be helpful in catching these symptoms early. Look for trends—are your workouts feeling good, are your goal paces requiring a little less effort, or is your endurance improving? If you notice gains, your body is responding well to the stress of training and balancing it well with life stress. If you notice consistent struggle or even setbacks in fitness, reevaluate your training and lifestyle stress load, as you may be on the path to overtraining.

Underfueling is a form of stress that can negatively impact training and health.

An adequate diet, with enough energy (calories) and nutrients to refuel the body and help it recover from workouts, is essential to fitness gains and overall health. Food provides the nutrients the body needs to rebuild and repair muscle tissue, replace glycogen (carbohydrate) stores, maintain immune health, and keep vitamin and mineral stores within a healthy rage. Fueling adequately becomes challenging for athletes with high volume training loads, or when training at high intensities, because maintaining these levels of activity can substantially change the body’s nutritional needs.

Signs of Underfueling


  • Constant hunger
  • Fatigue, low energy levels
  • Irritability
  • Intense cravings, or constant focus on food
  • Trouble sleeping
  • Hunger pangs during workouts
  • Gastrointestinal (GI) distress
  • Muscle cramps or weakness


  • Hypothermia (cold intolerance)
  • Stress fractures
  • Changes in, or complete loss of, a regular menstrual cycle (for women)
  • Significant weight loss

The following fueling tips are general, catered to the average population. To understand your individual needs, consult with a sports dietitian.

  • Eat before exercising, especially for high intensity workouts and long runs
  • Eat during exercise if the workout exceeds 60-75 minutes (I generally recommend fueling every 35-40 minutes)
  • Eat after exercising, a recovery meal or snack, followed by another meal or snack within a few hours if hunger strikes again.
  • Eat when hunger arises; avoid spacing out meals by a certain number of hours or condensing food intake to mealtimes only.
  • Use supplements as needed, and with recommendations from a sports dietitian or physician.

Overtraining and underfueling may walk hand in hand.

If a runner is experiencing chronically high stress levels (from training or otherwise), changes in sleep, mood, and appetite may affect everyday eating habits. Conversely, underfueling symptoms such as GI distress, lower energy levels, muscle cramps, or trouble sleeping make it hard to complete workouts as planned. This may lead to overexerting during specific exercises, and result in overtraining. And some runners are more prone than others: Perfectionism, high stress lifestyles, and a history of disordered eating are just a few of many risk factors that may result in overtraining or underfueling.

Build rest and recovery into your training plan.

Moehl uses micro and macro cycles of periodization to help athletes avoid overtraining. “I usually give athletes a three week build, then one week of easy, low-impact workouts,” she notes. She also advises periods of rest after a long training cycle. Her athletes are reminded time and again, “Recovery periods are the most important parts of training.” Eating a variety of foods and enough energy daily—to fuel your activity or specific training needs—can make sure your body has what it needs to rebuild during those recovery times.

Self-assessments can be a helpful training tool.

While a coach or sports dietitian will help identify trends that may lead to overtraining or underfueling, we also have to look out for ourselves. Tracking your heart rate is one objective measurement of stress and your body’s response to training. I use it consistently with myself and clients to make sure that “easy” days are done at an easy effort, to monitor fitness gains, and look for signs of overtraining (e.g. increase in resting heart rate, or having a hard time keeping heart rate low during easy workouts). In addition, the following questions may be helpful for self check-ins:

  • Am I sleeping well? Falling asleep quickly and staying asleep through the night?
  • Are my energy levels normal (for me) throughout the day?
  • Am I able to hit goal paces and efforts in my workouts?
  • Am I able to concentrate on tasks outside of training (e.g. work, family, relationships)?
  • Do I feel hungry throughout the day?
  • Am I enjoying foods I normally like to eat?
  • Do I feel full and satisfied after meals and snacks?

Be in tune with signs of stress and underfueling to avoid injury and fatigue.

An important part of any athlete’s training and education must be this awareness of the signs and symptoms for both overtraining and underfueling. Keeping a detailed training log may help identify trends, when symptoms begin, and how to correct them. As Brad Stulberg and Steve Magness mention repeatedly in their book, Peak Performance, “stress + rest = growth.” If stress is too high—from overtraining or underfueling, or both—additional rest will be needed in order for growth to continue. Working with a coach, sports psychologist, and a sports dietitian may be necessary to maintain health, avoid overtraining and underfueling, and reduce injury risk.