By Daniel G. Graetzer, Ph.D.
Faculty Member, School of Health Sciences
Sports conditioning is based on the overload principle, which states that a body system (for instance, cardiovascular or muscular) must be progressively stressed to increasingly greater intensities to help you achieve higher levels of fitness or strength. For example, running at 60% of your maximum capacity for 30 minutes three times a week for three months will increase your maximum aerobic power on a treadmill by about 15%. At this point, your fitness level will plateau unless you apply greater stress to your body.
But if your training intensity is systematically increased, a 40% increase in aerobic power can be achieved in the same amount of time. Overloading, however, can lead to overtraining when increases in exercise intensity and duration are excessive, and adequate recovery time is not allowed between workouts.
Overtraining is all too common. For example, a majority of elite athletes experience overtraining at some point in their careers. Overtraining tends to be more prevalent at the beginning of the peaking phase (immediately prior to the competitive season) of periodization training.
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General Adaptation Syndrome
Hans Selye, a famous Canadian physiologist, observed that when the body is put under stress (when its homeostatic balance has been upset), it will adapt in three distinct phases that he termed the General Adaptation Syndrome.
Regardless of the type of stress applied to a human body (exercise, illness, injury or psychological/emotional upset), Selye noted that the body’s response pattern will be the same. He also found that exposing the body to one type of stress sets up a therapeutic cross-resistance, which assists in protecting the body against other forms of stress. For instance, regular exercise strengthens the cardiovascular system and increases its tolerance against emotional tension, which could lead to high blood pressure or a heart attack.
Selye’s three-phase General Adaptation Syndrome consists of the alarm, resistance and exhaustion stages. The alarm phase is the first exposure to stress and causes the body’s defense mechanisms to be activated. This phase is followed by the resistance phase, during which the body builds strength and attempts to regain homeostasis.
If the body adapts, it gets stronger and reaches a higher level of conditioning. If the increases in load is excessive and the body is not given adequate time to adapt, the exhaustion stage results.
Selye showed that the timing of subsequent stressors is extremely critical. In a lab experiment, he observed that when rats were exercised and allowed to recover properly, their muscular systems supercompensated and they became much stronger. But if they were stressed and then stressed again before they had adequate time to recover, they became considerably weaker.
The figure below shows the body’s response to a periodization training program that progressively overloads the body and then lets it recover to achieve a higher level of fitness (homeostasis). The body’s normal response to an increase in training load (resistance stage) will result in transient fatigue and muscle soreness.
If this fatigue clears up in a few days (during the resistance phase), your body supercompensates, you achieve a higher homeostatic level and you gain a higher level of fitness. If you feel sluggish for several days or weeks, however, you may have exceeded your exercise/recovery tolerance and lapsed into the exhaustion stage. Overtraining occurs when there is a prolonged imbalance between exercise stress and recovery.
Image courtesy of author.
Other Causes of Overtraining
Overtraining can also be caused by sudden increases in training load – doing too much too soon – or inappropriate training such as improper weight training technique or the lack of a proper warmup and stretching. Highly motivated athletes are the highest risk for overtraining because the intensity of conditioning seems to contribute more to developing symptoms of overtraining than training duration.
Some athletes have overtrained due to the emotional stress brought on by excessive expectations by coaches or the news media. Chronic overtraining is usually associated with a combination of physical and emotional stress that exceed the athlete’s ability to cope with the stress.
Overtraining restricts athletic performance by reducing the body’s maximum work capacity and causing premature fatigue during endurance work. In an overtrained athlete, oxygen inhalation/exhalation, heart rate, and blood lactate will be higher and metabolic efficiency will be lower at a submaximum workload during exercise, compared to a well-rested competitor.
The symptoms of overtraining include:
- An elevated heart rate
- Severe and prolonged fatigue
- Decreased appetite
- Weight loss
- Increased incidence of infection and injury
- Iron-deficiency anemia
- Disturbed sleep
- Emotional irritability
The oldest-known indicator of overtraining is an increase in resting heart rate. Trained endurance athletes normally have lower resting heart rates due in part to the stronger heart muscle pumping out more blood per heartbeat.
Distance runners who developed overtraining by quickly doubling their training mileage revealed an increase in their morning heart rate of over 10 beats per minute. A delayed return of normal resting heart rate following exercise is also sometimes seen in overtrained athletes, because heart rate recovery may take up to two hours instead of returning to normal in three to four minutes. These heart rate changes are probably due to chronic fatigue of the heart and a general increase in sympathetic nervous system activity.
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How to Avoid Overtraining
The best strategy to prevent overtraining is a systematic and progressive periodization of training program in combination with adequate rest. Sudden large increases in training load and inappropriate training should be avoided.
Reducing your training intensity, allowing adequate recovery between high-intensity workouts, avoiding monotony in training and getting 7.5 to 8.5 hours of bed rest each night are recommended. Manipulating your diet by increasing iron intake, your total number of calories consumed or the percentage of healthy carbohydrates in your diet has also proven useful for people seeking to safely improve their physical fitness.
Keeping records of your resting heart rate, body weight, fluid consumption, and patterns of muscle soreness throughout the various phases of your training will also help you better determine when it’s time for the next increase in your training load. Many university with a sports/exercise science department can determine if you are overtraining through exercise testing, diet and blood chemistry analysis and psychological assessment.
If you are overtraining, the frequency of your workouts should be dropped to twice a week. Research has shown that two high-intensity exercise bouts per week will allow your general fitness to be maintained.
Conditioning should take a more recreational attitude with no athletic competitions until the athlete has properly recovered. Keep in mind that if severe overtraining develops, a prolonged layoff may be required and could possibly ruin an athletic season. If complete bed rest is needed, maximum aerobic power will decline by approximately 25% in 20 days.
Undertraining Is Sometimes Preferable to Overtraining
Overtraining is a common, serious problem in sports, and athletes are better off undertraining than overtraining in many instances. Transient muscle soreness and fatigue are essential to the conditioning process but if they persist for several days or weeks, a relative degree of overtraining is developing.
There is a delicate balance between overload and recovery. To maximize your body conditioning, you must sometimes risk overtraining. It’s important to remain aware, however, that being at your absolute peak of physical fitness is one step away from losing it all, so avoiding injury due to overtraining is critical.
A critical aspect of coaching is to prescribe the optimal progression of amount and intensity of conditioning without exceeding an athlete’s exercise tolerance and recovery capacity. Periodization training with adequate rest is the best strategy to gain maximum performance development without chronic fatigue.
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