Overtraining Syndrome, Part One: An Overview

A look at overtraining syndrome and its cause.

By on September 10, 2013 | Comments

Stay the CourseHappy September! The year is flying by, and the major spring build-up races have ceded to the summer championship races, the Grand Slam of Ultrarunning, the Ultra-Trail du Mount-Blanc, to name a few. These races then cede to even more “championship” races in the fall and winter.

[Editor’s Note: The article was followed up with Part 2: Treatment and Prevention and Part 3: The Trail Ultrarunning Specifics.]

Between all those races, we’re also sneaking in the occasional circumnavigation, and taking on an FKT or two in our spare time. And, of course, we have train hard to prepare for all these events.

Perhaps you can see where I’m going with this.

Ultrarunning is a pursuit built upon the notion that victory, triumph, and accomplishment is borne through suffering: perseverance of tough times, profound fatigue, blown legs, trashed stomach, and punch-drunk minds. We are rewarded–tangibly, electronically, and pharmacologically–when we endure the distance, the suffering, to the finish.

Those rewards–along with the beauty of scenery and the strength and support of the community–provide ample desire and motivation to participate even more.

If suffering and the overcoming of that suffering are so paramount to the ultrarunning experience (and perhaps, not exceeded by any other “sport” in society), how can one objectively discern between good suffering–physical toughness, character-building, and mind-galvanizing–and bad suffering–that which causes severe physical and/or psychological damage, and which may be irreversible?

Overtraining is a topic familiar to most runners: the notion that there is such a thing as too much of a good thing. For most, the consequences of overtraining are straightforward, often tedious, but infrequently disruptive: overuse injuries to muscles, tendons, joints, and bones; or fatigue and flat performance.

What many runners–and perhaps an even greater proportion of ultra-endurance athletes–fail to realize is that prolonged overtraining can have devastating effects not just to run performance but to one’s basic quality of life, stripping them of the energy and vigor to enjoy daily life.

This is part one of a multi-part series on overtraining: the background, physiology, diagnosis, and treatment; and implications for competitive and recreational ultramarathoners.

Overtraining: Definitions and Background

In their review of current literature titled Overtraining syndrome: a practical guide, Doctors Jeffery Kreher and Jennifer Schwartz (2012) define overtraining as, “a maladapted response to excessive exercise without adequate rest, resulting in perturbations of multiple body systems (neurologic, endocrinologic, immunologic) coupled with mood changes.”

This definition of Overtraining Syndrome (OTS), represents the most severe form of maladapted stress/rest response. They make a distinction between OTS and the less-severe condition of overreaching:

Condition Characteristics Duration Effect
Functional Overreaching (FO) Mild excess in training load, resulting in temporary performance decrease, then improved performance after rest Days to weeks* Positive (“Supercompensation”)
Nonfunctional Overreaching (NFO) Intense training resulting in more prolonged performance decrease; presence of neurological, hormonal, and/or psychological effects Weeks to months* Negative: symptoms, time lost in training, competition
Overtraining Syndrome (OTS) Extreme NFO with >2 months performance decrement, severe symptoms and physiological changes (psychological, neurological, endocrine, immune), as well as other stressors, all unexplained by other diseases. Months to years# Negative: severe symptoms, unable to train, affecting activities of daily living, possible end to athletic career

Adapted from Kreher and Schwartz, 2012

(* even with compete rest)

(# some effects may be irreversible)

True overtraining goes beyond simply running–or engaging in any workout modality–to excess. Critical defining qualities of full-blown OTS include a complete inability to physically exert oneself, multi-system physiological responses, and a failure to respond to even prolonged rest.

Unfortunately, there are still many questions about overreaching and overtraining, including the notion that the progression may not be a continuum; some athletes may jump from FO straight to OTS.

Symptoms of OTS

In his all-things-running book, Lore of Running, Tim Noakes (2003) offers a review of evidence-based signs and symptoms of the OTS continuum.


  • Loss of enthusiasm and drive; apathy, loss of joy in life
  • Loss of joy/thirst for competition; increased desire to quit during competition
  • Lethargy, listlessness, tiredness
  • Increased irritability, anxious, depressed, unable to relax, bored
  • Insomnia, changes in sleep patterns
  • Loss of appetite
  • Loss of libido
  • Poor coordination, general clumsiness
  • Increased fluid intake/thirst (namely in p.m.)


  • Impaired physical performance; inability to complete routine training
  • Gradual loss of weight
  • Athlete looks drawn, sallow, dejected; sunken eyes
  • Increase in morning heart rate > 5 beats
  • Abnormal heart rate upon standing, during/after routine training
  • Slower recovery in heart rate after exertion
  • Postural hypotension
  • Persistent, progressive muscle soreness
  • Swelling of lymph glands
  • Gastrointestinal disturbances (with, without exertion)
  • Increased susceptibility to infection, allergies, headache, injury
  • Decreased tissue healing (minor scratches)
  • Loss of menstruation
  • Neurological, endocrine insufficiency

Incidence of OTS

While true, diagnosable OTS may be rare (at least in its recognition; it is often misdiagnosed as another disease process), incidence of overreaching, especially amongst runners, is high. One study of distance runners found a NFO lifetime prevalence of nearly 60% in elite male and female runners, and 33% in non-elite female runners (Morgen et al, 1987). Anecdotal evidence, especially within the ultramarathon community, might suggest similar incidences.

Causes of Overtraining

Much research has been conducted into the pathophysiology of OTS: what, exactly, is occurring in various systems to cause it and what perpetuates symptoms, despite periods of prolonged rest. Theories include inadequate muscle energy stores, excess tissue oxidation, and metabolic stresses to nerve and glandular tissue. One leading theory is that systemic inflammation from chronic training excess drives the adverse effects seen with multiple body systems.

Looking at the big picture, OTS and its continuum of conditions is caused by two primary factors:

  • excess training load
  • inadequate rest

However, there is a third factor that seems to be present in the most severe, persistent cases of OTS: additional physical or psychological stressors. Kreher and Schwartz point out that, in cases of OTS, other stress factors are present.

Lower-intensity but repetitive factors:

  • training monotony
  • sleep disturbances
  • altitude exposure
  • life stresses (work, family, relationships)

Lower-frequency, but higher-intensity stress factors:

  • repetitive competitions
  • significant illness
  • heat-injury episodes
  • severe “bonk”

Indeed, it is the addition of another dimension of physiological stress–coupled with an unremitting training load and lack of rest–that most commonly causes the continuum of overtraining syndromes.

Diagnosis of OTS

In order to be diagnosed with OTS, three criteria must be met:

  1. Decreased performance “despite weeks or months of recovery”. This is a critical component of diagnosis of true OTS (versus FO or NFO). A distinguishing factor of OTS–versus other organic disease processes–is that the runner often demonstrates the ability to start a training session, but is unable to finish it.
  2. Disturbances in mood. Pervasive mood changes–both in and out of training–are present, usually coupled with the high workload and other life stressors.
  3. Lack of signs/symptoms of other conditions or disease processes.

It is important for athletes and health-care practitioners alike to rule out other disease processes, including asthma or other lung sensitivities, thyroid or adrenal dysfunctions, diabetes, iron deficiency, infections, and malnutrition.

But the fact of the matter is, when a runner is suffering from an OTS condition, he or she is frequently in denial that simply excessive training (or life) stress coupled with inadequate rest could cause their symptoms. Therefore, they (as many runners do) are apt to consider more sinister disease processes before conceding to OTS.

When symptoms matching OTS present themselves, the single most important first step is to stop running. Period. Only then can an accurate diagnosis be made; and even then, it may take a period of weeks or months of rest for symptoms to abate.

Testing for OTS

Comprehensive blood and metabolic testing may be helpful in ruling out metabolic and/or cardiovascular diseases, especially if the runner is new to the sport or is in the masters-plus age range (>40 years old). However, research into specific testing for OTS has found a lack of consistent markers/testing thresholds, including hematologic (iron, RBCs, CPK, etc.), inflammatory markers (cytokines), oxidative chemicals, immunologic, or hormonal (cortisol, testosterone). All these values can be normal in cases of OTS.

Functional Testing for OTS

Interestingly, the most reliable tests for the OTS continuum are functional: how do basic metrics line up with exercise-based tests? In a laboratory setting, athletes with OTS demonstrate differences in sub-maximal, maximal, and post-exercise recovery rates of heart rate, oxygen uptake (VO2Max), and blood lactate levels.

But it’s even simpler: standard exercise tests–simply running a standard loop or course (in relatively standard environmental conditions) and comparing perceived effort (Rate of Perceived Exertion – RPE), heart rate, and time–can detect both overreaching and overtraining.

Quite simply, are you running slow, trying harder, and is your heart beating faster on a given course than before? If so, you’re overtrained.

Effects of OTS

The effects of overtraining go far beyond being tired, running slow, and getting injured. Below are significant, pathological–and possibly irreversible–effects seen both clinically and in research, as a result of chronic overtraining:

Metabolic and Neurological Effects

The systemic effects of the OTS continuum result in an over-stressing of the very systems used during exercise: the neurological and endocrine systems.

During exercise, the sympathetic nervous system–in charge of “fight or flight” responses–is strongly activated. In response to the demand of training and racing, heart rate elevates, blood pressure rises, and muscles fire more powerfully. Additionally, various “resting” systems (such as the digestive tract) are slowed to prioritize the active fight/flight needs. Metabolically, the hypothalamus, pituitary, and adrenal glands secrete hormones during and after exercise to facilitate performance of the heart and skeletal muscles. They also help moderate inflammatory stresses involved in physical exertions.

Like other overuse conditions–such as Type II Diabetes–overtraining results in two problems with the neurological and endocrine systems: a fatigue-based decrease in output. The nerves fire more weakly; the glands secrete less hormones; and a desensitization–less responsiveness–of the affected tissues occurs. In short, they fire less, and the body needs more of it to react. Indeed, runners with OTS will frequently be diagnosed with Addison’s Disease, insufficient cortisol production or sensitivity. Symptoms include, “depression, progressive weight loss, an inability to maintain blood pressure when standing, and severe physical incapacitation” (Noakes, 2003).

The bulk of both physical and psychological symptoms of OTS are due to compromised nerves and glands. And since these tissues, when damaged or compromised, regenerate extremely slowly (if ever), recovery from a neurological or endocrine injury can take months, or years. Or, these changes may be permanent.

Muscle Tissue Damage

Physiologists have been studying muscle tissue damage in runners for over three decades. The prevailing notion is that training and racing volumes that do not cause soreness, presumably, do not cause significant damage, either short- or long-term. However, the bulk of marathon and ultra training and racing does just that.

Some notable research findings on muscle tissue damage include:

  • Up to 25% of muscle fibers are damaged after marathon and ultramarathon performances. This should surprise no veteran of ultra racing. However, further results may.
  • Muscle cell damage has been shown to take up to 10 to 12 weeks to fully repair.
  • In some studies, many athletes demonstrated “areas of fibrosis”, suggesting incomplete repair or chronic muscle cell damage, even in samples taken pre-competition. This lends support to the theory that muscle cell damage is cumulative and chronic, and possibly impervious to rest, stretching, and myofascial tissue mobilization.
  • Abnormalities of mitochondria in muscle cells exist in severely overtrained athletes. This may indicate systemic changes to how muscle cells function–at their most basic, metabolic levels–with prolonged stress. (Noakes, 2003)

While these findings are troublesome, perhaps most frightening is a recent study by Collins and colleagues (2003) that has shown changes to DNA structure in the muscle cells of chronically overtrained athletes. DNA is critical to efficient and accurate cell replication, namely in repair and regeneration. DNA telomeres are end-caps, protecting the DNA strand from deterioration or alteration. Shortened telomeres are thought to result in significant reduction in cell replication, and may result in slight alterations to subsequent generations of cells.

Simply put, the blueprint to strong, healthy muscle cells loses its protection and possibly its ability to quickly and accurately repair and regenerate muscle cells. Scientists theorize that this telomere shortening is irreversible and permanent.

The bottom line is, prolonged muscle stress may permanently change the DNA structure of muscle cells to weaker, less responsive tissue. And that this skeletal muscle genetic material damage is related to the amount of training and/or racing done on sore muscles.

OTS, Muscle Damage, and “Fatigued Athlete Myopathic Syndrome” (FAMS)

Athletes who suffer from OTS whose dominant symptom is muscle soreness, have been categorized as having a condition called Fatigued Athlete Myopathic Syndrome, defined as, “persistent muscle soreness, unexplained fatigue, and rapid and sustained fall in athletic performance” (Derman et al, 1997). The hallmark of FAMS is that, despite full rest–as well as recovery of the metabolic and neurological symptoms consistent with OTS–the athletes continue to demonstrate what Noakes calls “a catastrophic loss of running ability.” Their muscles will simply not allow for previous running intensities or durations without significant, lasting effects. It is thought that the metabolic and nucleic changes seen in previous studies might explain this phenomenon, but the relationship is uncertain.

What is not uncertain is that FAMS is a legitimate condition that affects an unknown number of previously active, highly competitive runners who are otherwise healthy and disease-free.

To conclude, Noakes adds the following, regarding the sensitivity, and perhaps finite capacity, of muscle tissue:

“Muscle is a fragile organ and can clearly be damaged in ways that we have yet to understand fully”


“Skeletal muscle of athletes whose exercise capacity becomes impaired after many years of heavy training lose their capacity to regenerate when re-damaged by training or racing. These changes have occurred at the level of the athletes’ genetic material and are hence irreversible” (Noakes, 2003, p.503)


There is much that is yet unknown about Overtraining Syndrome and its spectrum of conditions. But my hope is that the reader comes away from this missive with the following understanding:

  • Overtraining is more than simply being tired, running poorly, and getting injured.
  • OTS can result in irreversible changes to multiple body systems, causing permanent changes to not only running capacity, but one’s overall quality of non-running life.

It needs to be taken seriously.

The sport of ultramarathon running–namely trail ultramarathons–poses unique and arguably greater challenges to predicting, preventing, and overcoming Overtraining Syndrome. Soft, variable trail surfaces and lower-intensity running masks–but does not prevent–the effects of the extreme load that running 30 to 100-plus miles places on our bodies. Moreover, the psychosocial factors of running in beautiful places amongst our fun-loving, supportive (if not, at times, peer-pressuring) ultrarunning community compounds the drive to do more than the body is willing and able to accept.

In subsequent columns, we will investigate treatment, prevention, and implications for the ultramarathon running community and how concepts of overtraining may affect the future of the sport

Call for Comments (from Meghan)

  • Have you had a doctor’s diagnosis of something on the overreaching and overtraining spectrum? If so, what were your symptoms and how were they treated?
  • For those of you with anecdotal, undiagnosed, first-hand experience with overreaching or overtraining, what did it feel like to you and have you been able to heal yourself?


  • Athletes with exercise-associated fatigue have abnormally short muscle DNA telomeres. Collins M, et al. Med Sci Sports Exerc. 2003 Sep;35(9):1524-8.
  • Lore of Running, Noakes. Human Kinetics; 4th Ed. (2003)
  • Overtraining syndrome: a practical guide. Kreher JB, Schwartz JB. Sports Health. 2012 Mar;4(2):128-38.
  • Psychological characterization of the elite female distance runner. Morgan WP, O’Connor PJ, Sparling PB, Pate RR. Int J Sports Med. 1987 Nov; 8 Suppl 2():124-31.
  • The ‘worn-out athlete’: a clinical approach to chronic fatigue in athletes. Derman W, et al. J Sports Sci. 1997 Jun;15(3):341-51.
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Joe Uhan

Joe Uhan is a physical therapist, coach, and ultrarunner in Auburn, California. He is a Minnesota native and has been a competitive runner for over 20 years. He has a Master’s Degree in Kinesiology, a Doctorate in Physical Therapy, and is a USATF Level II Certified Coach. Joe ran his first ultra at Autumn Leaves 50 Mile in October 2010, was 4th place at the 2015 USATF 100k Trail Championships (and 3rd in 2012), second at the 2014 Waldo 100k, and finished M9 at the 2012 Western States 100. Joe owns and operates Uhan Performance Physiotherapy in Eugene, Oregon, and offers online coaching and running analysis at uhanperformance.com.