Overtraining is directly caused by chronic overexertion and poor recovery, but psychology, nutrition, and other health factors can all contribute to shifting the balance between exertion and recovery. Some hypotheses for the mechanisms behind OTS (Overtraining Syndrome) include the glycogen hypothesis (low glycogen corresponding with fatigue), central fatigue hypothesis (explains mood shifts), and the oxidative stress hypothesis (muscle damage via excessive oxidative stress). Unfortunately, none of these hypotheses provide a complete explanation of all symptoms of overtraining syndrome, but along with other theories, they collectively explain the syndrome and may offer insight into how to recover from overtraining.

Remember that overtraining is a progression requiring chronic exposure to over-stimulus. Below are the three types of responses to exercise and how to evaluate your recovery status.

Functional Overreaching: The exercise stimulus is enough to develop your abilities as an athlete, but you are able to recover in time for the next workout and continue to improve.

Non-Functional Overreaching: The exercise stimulus isn’t enough to prevent you from sticking to your training schedule. However, you will not be recovered enough by the next workout to make optimal training gains.

Overtraining Syndrome (sometimes called OTS): You have been training at the Non-Functional Overreaching level for weeks or months, and the accumulated fatigue has put you into a state of overtraining.

If you suspect that you might have progressed past Non-Functional Overreaching and into Overtraining Syndrome, then you should assess for the following symptoms:

Primary Symptoms of Overtraining

Loss in performance

The main indication of being overtrained, or having overtraining syndrome (OTS), is the paradoxical loss in performance despite continued training.

If you find yourself experiencing a confusing decline of improvement but have been increasing your training volume and intensity, you may be overtrained. You are under-recovering and have not realized it.

Chronic Fatigue

A lingering and persistent fatigue can be another major indicator of overtraining. If, after rest days, you are unable to experience a reinvigorated feeling or sense of muscular strength and coordination, then additional rest is required. If you’re in this bucket, focusing on recovery for 5-7 days will allow you to bounce back.

Secondary Symptoms of Overtraining

Muscle Tenderness

Lasting muscle tenderness and pain after training sessions.

Mood Shifts

Inexplicable changes in mood during the day. If you catch yourself experiencing reactions or shifts in temperament that aren’t normal for you, consider rest.

Depression, Irritability, and Anxiety

Similar to mood shifts, other psychological symptoms of overtraining or OTS can be similar to other forms of burnout. Your friends and romantic partners may notice this before you do. Ask them.

Loss of Appetite

Overtraining can cause a change in appetite due to disturbances in the autonomic nervous system that suppress hunger. This severely exacerbates your ‘under-recovery’ and is a sign that you need to get into recovery mode ASAP.

Impaired Immune System

It is well established that normal training briefly suppresses the immune system’s ability to fight infection and illness, but due to the chronic nature of overtraining, the immune system remains suppressed. This can have profound impacts as the athlete is unable to recover from illness properly or finds themselves in a cycle of minor illnesses that inhibit or prevent any further training. While rest is the key to recovery, due to the maladaptive nature of overtraining, it is not always clear if the immune system will fully recover. This represents a major hurdle in the athlete’s path back to performance. In worst-case scenarios, some athletes’ immune systems are thought to become permanently compromised.

Low Motivation

In addition to the other psychological symptoms of overtraining, there may be a decrease in motivation for normal training and daily life. Motivation will always fluctuate, so there’s no need to worry if you’re not experiencing other symptoms and just feeling unmotivated. It can also be difficult to track motivation in overtrained athletes because, despite being unmotivated, they continue to train harder than ever. As with all symptoms described here, place them in the context of how you’ve been training and what else you might be feeling.

You do not need to show all these symptoms of overtraining, but it’s important to know the symptoms in case you suspect you have stepped the line. This is not a comprehensive list of symptoms since new research may point to additional markers of overtraining and, hopefully, a better understanding of its key mechanism.

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As chronic stress due to exercise continues to build in the body, there is a cascade of disruptions in the biochemical processes that contribute to decreased exercise performance. This plateau or decrease in performance is the hallmark of overtraining syndrome.

Below is a more detailed description of where these symptoms originate:

Disturbed Autonomic Nervous System: Changes in resting heart rate, loss of appetite, chronic fatigue, loss in performance.

To quickly review, the autonomic nervous system is divided into the sympathetic and parasympathetic systems and is responsible for involuntary processes in the body. These include changes in heart rate, muscles used for digestion, vasoconstriction, respiration, blood pressure, and other important processes.

The autonomic nervous system plays a critical role in all exercise and training by mediating changes in heart rate to match levels of activity and increasing or decreasing vasoconstriction to optimize blood flow to working muscles and maintain the blood process. Overtraining impairs these processes.

Impaired muscle recovery: Reduced muscle hypertrophy and repair, muscle tenderness

The maladaptations created through overtraining can turn normal positive adaptations to exercise into negative ones.

An example is impaired muscle recovery, including lower muscle growth and the ability to repair existing muscle fibers. An improvement in skeletal muscle is probably the definitive example of a positive response to exercise. To over-simplify it: You workout, and your muscles get better. If, for any reason, your strength and endurance are not improving after being exposed to an appropriate stimulus, then there is something wrong. In the case of overtraining, this is likely due to a combination of oxidative stress, very low glycogen availability, and chronic exposure to metabolites.

Impaired lactate clearance: Reduced muscle function during exercise, lower energy levels, loss in performance

The ability to clear lactate decreases as the body continues to maladapt and undergoes massive, chronic oxidative stress. Lactate is a primary energy source during submaximal exercise, but the ability to effectively remove lactate is reduced when overtrained. This results in two things; firstly, you will hit your lactate thresholds at lower activity levels; secondly, blood lactate will accumulate faster and stay longer, leading to reduced recovery. Oxygen is the key to lactate clearance, and as with other symptoms, chronic stress on the oxidative system may impair lactate clearance.

Psychological disturbances: Mood shifts, depression, irritability, anxiety, low motivation

Changes in psychology due to overtraining have mostly been attributed to disturbances in the autonomic nervous system. Psychological symptoms of overtraining do not typically have a clear onset and may also be a primary cause for the syndrome itself.

Regarding overtraining, rest is the only known physical solution, but an effective strategy would also include counseling or other forms of mental health care.

Chronic mental exhaustion: Burnout

Similar to the other psychological disturbances, burnout and a feeling of mental exhaustion are consistently seen in overtrained athletes. Continuing to train in spite of this mental burnout, with the misguided idea that you won’t be able to get better unless you keep training, is common.

In overtraining, rest is the only known physical solution.

Reduced neuromuscular coordination: Loss in performance

In connection with the autonomic nervous system, reduced neuromuscular coordination is a very common and possibly an early sign of overtraining. A normal response to training is an increase in reaction time, fine motor control, and coordination during movement patterns. For example, a healthy, well-trained trail runner will be able to skip through a scree field because they trust in their body’s ability to react accordingly. In the overtrained, despite best efforts, the body may not effectively respond to the commands from the brain, and you may feel clumsy or uncoordinated. This is known as ataxia, and if you actually struggle to walk on normal surfaces, or lose your balance to the point of falling down, see your medical doctor.

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If you suspect that you might be overtraining or are already overtrained, and two or more of the above symptoms speak to you, you should rest. The amount of mental and physical energy required to push into an overtrained state is huge, so it’s important to recognize when you feel like you aren’t recovering and improving. Recognizing OTS early will almost always prevent its continued onset, and using the symptoms as a handrail will keep you happy and healthy.

Home Testing for Overtraining

A simple way to test for, and monitor, overtraining is to track your heart rate across your aerobic workouts, runs, hikes, or other endurance-related activity.

As every Uphill Athlete knows, as we train, there should be a long-term decrease in heart rate when performing submaximal efforts.

When we are in an overtrained state, there are disturbances to this system that will be reflected by a higher-than-expected heart rate when training. It is important to consider other known symptoms of overtraining when interpreting your heart rate data because factors such as cardiac drift (progressive increases in heart rate during exercise, mostly due to heat) may affect your readings.

A good rule of thumb would be, if you suspect that you might be overtrained, to monitor your heart rate over 2 or 3 sessions and see if there is a consistently high reading. However, if you are showing a number of major symptoms and also have a high heart rate reading during a submaximal workout, then it is far better to rest than continue attempting to test.

I recommend doing these only once or twice in the build-up to UTMB, ideally 4-6 weeks before the race. You can include another one 8-12 weeks before the race if you can.

You can plan a destination trip or training camp if you don’t live near conditions similar to Chamonix. Take two full easy days or rest days before and after these big adventures.


Overtraining syndrome (OTS) is a serious condition that can have detrimental effects on an athlete’s performance and overall well-being. It is important to recognize the symptoms of overtraining, such as a paradoxical loss in performance, chronic fatigue, muscle tenderness, mood shifts, and impaired immune system, among others. These symptoms can originate from disruptions in the autonomic nervous system, impaired muscle recovery, impaired lactate clearance, psychological disturbances, chronic mental exhaustion, reduced neuromuscular coordination, and other physiological factors.

Monitoring your heart rate during workouts can provide insights into your recovery status, but it should be considered alongside other symptoms for a comprehensive evaluation. By recognizing the warning signs of overtraining and addressing them promptly, athletes can avoid further progression of the syndrome and maintain their physical and mental well-being.

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