Overtraining in Endurance Athletes: Signs, Symptoms, and Prevention

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The syndrome of overtraining is common in nearly all endurance sports and fitness activities. Overtraining occurs when an athlete performs more training than the body can recover from, to the point where performance declines and symptoms may linger for weeks or months. One research study found 64 percent of elite female runners and 66 percent of elite male runners have experienced overtraining. Similar figures are found among triathletes, swimmers and cyclists. So why this high occurrence?

Many highly motivated athletes and recreational sportsmen are obsessed with training and are afraid to rest. They believe the harder they train the faster they'll run, despite evidence to the contrary - they train to the point where the standard two or three days of light exercise or complete rest won't allow them recovery. 

In extreme sports, we are encouraged to overdo things; which makes it the coach's job to ensure athletes don't overdo their training. Sometimes it means holding them back enough to recover. 

Adaptation and the progressive overload training principle

For improvement, well-designed training programs use the principle of progressive overload - a constant increase in training stimulus. As you increase your training workload your body responds by adapting to this increased stress (often called super-compensation). Then you overload again, your fitness improves to a new level, and the process repeats itself. This is the only effective way to continually improve performance. 

However, you cannot continue to increase the volume and intensity of training in a linear fashion; eventually you'll reach a point of overtraining. Proper conditioning requires a balance between overload and recovery - a fine line indeed, as your adaptation to a new training load varies even from day to day.

Causes of overtraining

Rapid increases in the frequency, intensity or duration of training sessions, without programming recovery, can result in overtraining. Swimmers, cyclists and runners who increase the frequency of their interval training sessions, compete in too many races or suddenly increase their mileage too quickly can experience overtraining symptoms.

Identifying and diagnosing overtraining

It's difficult identifying overtrained athletes, because many consider excessive ongoing fatigue as part of their normal training effort. And there's no simple blood test or clinical diagnosis. It's an individual phenomenon, and people exhibit different symptoms. 

The best we can do is recognize general symptoms early, then rest and recover. How do we recognize overtraining? Dr. David Costill, in his book Physiology of Sports and Exercise, and other researchers have identified many symptoms: 

Physiological symptoms of overtraining

• Muscle/joint tenderness, tiredness, tightness
• Decreased performance
• Increased rate of overuse injuries
• Insomnia/disturbed sleep patterns
• Body weight loss
• Nausea
• Decreased appetite
• Allergic reactions
• Elevated heart rate and blood pressure
• Head colds/persistent URTI
• Training fatigue/lethargy
• Higher lactate concentrations at any given workload
• Changes in menstrual pattern
• Decreased coordination
• Decreased heart rate at a given level of running intensity (about five beats/minute)
• Decreased strength
• Decreased maximal heart rate 
• Decreased muscle glycogen levels

Theories of overtraining

What does science tell us about overtraining? Recent research suggests that it affects the nervous and endocrine systems. Another theory holds that excessive trauma to the muscle cells without adequate healing causes a catabolic (breaking-down) state instead of an anabolic state, where the body regenerates itself. 

Systems affected by overtraining

Overtraining affects the musculoskeletal, immune, endocrine, cardiovascular and nervous systems. Stressors such as lack of sleep, jet lag, ongoing illness, work-related stress, poor nutrition and menstruation can exacerbate symptoms.

The hormonal system is heavily affected because your body releases stress hormones such as adrenaline (epinephrine) when you exercise. These increase heart rate, shunt blood to working muscles, release glucose into the bloodstream and stimulate your metabolism to burn more fat. 

Overtraining also causes an abnormal response in the autonomic nervous system from excess production of adrenaline - which in turn suppresses the body's production of serotonin and dopamine, (hormones that have a calming effect on us) causing us to experience the symptoms of depression and anxiousness seen in the table below.

Effects of overtraining on the hormonal system

Symptoms of overtraining affecting the autonomic (parasympathetic) nervous system:

• Irritability/moodiness
• Emotional instability
• Depression
• Elevated basal metabolic rate
• Lack of enthusiasm for training
• Anxiousness
• Lack of concentration
• Palpitations

If these symptoms don't get your attention, here are two that will: diminished sex drive and sexual performance, and fear of training.

Other research on overtraining

Research shows decreased iron oxide production in the bone marrow at hemoglobin production sites, a higher oxygen uptake and heart rate and lactate levels at normal training intensity in overtrained athletes.

Other undesirable changes are muscle fiber and mitochondrial abnormalities and alterations in the genetic material of over-exercised muscle. Other studies found glycogen depletion in overtrained runners, because they fail to eat enough carbohydrates to match their caloric demands. 

The immunosuppressive effect of overtraining

Research has shown that mild to moderate exercise actually boosts your immune system, but ironically, overtraining precipitates many undesirable hormonal and biochemical side effects that can grind your body to a halt and make you sick.

A reduction in leukocytes (white blood cells) and cytokines, your body's infection fighters - such as lymphocytes and antibodies - has been found with overtraining: meaning you have more chance of illness and infection and resultant complications. Many studies show heavily trained athletes catch colds easily. One study finds that half-Ironman triathletes are five times more likely to catch a cold than someone who trains without competing.  

Recovering from overreaching and overtraining

Once overtraining symptoms have set in, time is needed for your body to rebuild. For athletes who've simply overreached for a few workouts, a cessation or reduction in training for a few days (three to five) may be all that is necessary. 

After several weeks of overtraining, on the other hand, you'll need 10-14 days of reduced training; a 40 percent reduction of normal training load to bounce back, for up to three weeks if you've chronically overtrained with prolonged grueling schedules lasting several months.

Overtraining recovery strategies

How then can we avoid the scourge of overtraining? First, monitor yourself for symptoms, and react immediately if they appear. Here are some recovery strategies and advice on how to do this. 

The use of a heart rate monitor can assess whether a runner is working harder than normal to achieve the same pace and distance, but it's just as helpful to use common sense, and if you're feeling exhausted, cut back until you bounce back.

The real key to avoiding overtraining is prevention itself - by far the most effective method. This should involve use of periodized programs, where one week of lower-intensity and lower-duration training every three or four weeks will permit adequate recovery of the muscle tissue and energy refueling. Consult a local club coach if you are interested in creating this sort of program. V 

Roy Stevenson has a master's degree in coaching and exercise physiology from Ohio University. He coaches runners and triathletes in the Seattle area, and teaches Exercise Science at a university and community college in the Puget Sound.

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