Among chronic exercisers, there is always the potential of doing more but receiving less. What many exercisers do not realize is that additional workouts can sometimes lead to the law of diminishing returns, where anticipated responses do not occur. It has been well established that in order to receive a training effect, the exerciser must experience some fatigue. This fatigue will in turn induce a need for recovery, which leads to a period of overcompensation or the training effect. However, if there is little or no recovery, combined with additional intense activity, the overcompensation or training effects do not occur, and overtraining symptoms can be observed. The term overtraining has been used interchangeably with staleness, burnout, chronic fatigue, stagnation, overwork or run down. Researchers have reported no less than 31 features of overtraining extending to 84. The most prominent features of overtraining include heavy legs, sore muscles, high resting heart rate, poor motivation, sleep disturbances, low libido, frequent sickness or infection, weight loss, depression and increased rating of perceived exertion.
- Overtraining: State of the Art Review No. 26, Traeger Mackinnon, L., & Hooper, S (1992), Excel. 8: 3-12
Overtraining occurs when an athlete has been exposed to prolonged high intensity, high volume training, which manifests itself in an accumulated fatigue state. It has been reported under over reaching, burnout, staleness etc. Athletes generally experience a deep and prolonged fatigue, poor performances and at times an inability to train and compete at the highest level.
The prevalence of overtraining appears to be specific to certain sports and exercise activities. Elite distance runners tend to demonstrate higher levels of overtraining, as do female athletes who tend to follow the coaches’ instructions without question.
The three major causes of overtraining reported are inadequate recovery between sessions, excessive amounts of high intensity training and sudden increases in training load. General exercise prescription for overloading has recommended increases of no more than five to 10 percent. Other factors reported include too much intense strength training, too many competitions and travel and no breaks between training seasons. It is unusual to see overtraining symptoms in exercisers who maintain high volumes of low intensity training or moderate long term training.
An athlete’s lifestyle and the stress associated with it can contribute to overtraining. These may include poor nutrition, inadequate sleep, psychological conflict and an inability to achieve set goals.
The physical symptoms of overtraining include: poor performances, unable to maintain training load, chronic fatigue, elevated resting heart rate, hormonal changes, low serum ferritin levels, high blood pressure, continual muscle soreness, sudden weight loss, headaches, frequent sicknesses and menstrual irregularities. Emotional symptoms are: depression, poor self confidence, mood changes, apathy, lethargy, low motivation, poor sleep habits, irritability, boredom, poor appetite, inability to relax and anger.
It is of some concern that when these symptoms are recognized, it is often too late for adequate recovery before competition. Overtraining symptoms appear to be very much an individual response, and many times, an individual will exhibit a combination of symptoms. As a rule of thumb, one of the best indicators is still prolonged fatigue lasting one week.
Prevention of Overtraining
Overtraining often requires extensive recovery. Elite athletes are always pushing the limit and as such train very close to the overtrained state. In this case, it is much more effective to prevent the overtrained state rather than treat it. Overtraining can be prevented by individualizing training programs, monitoring fatigue levels, increasing training load gradually, encouraging variety in workouts, scheduling rest days, providing breaks between seasons, encouraging good nutrition and including regenerative techniques such massage, relaxation and hydrotherapy into the training program.
Athletes can be monitored by tests such as resting heart rate, periodic heart rate recording at sub maximal workloads, perceived level of fatigue (1-7 level) or time trial over a selected distance.
Responses to Overtraining
Heart Rate - Monitoring heart rate both at rest and during sub maximal exercise appears to be good indicator of overtraining. When taking resting heart rate, an elevation of six to 20 beats above normal as well as a 25 beats/min increase during sub maximal exercise can indicate overtraining potential. It is important to remember that other factors can also affect heart rate such as illness, stress, dehydration etc.
- Blood Pressure - Systolic blood pressure in the overtrained state may be increased at rest and after standing from a supine position as well as during sub maximal exercise.
- Oxygen Consumption - Maximum oxygen consumption may decrease five to 10 percent during overtraining.
- Blood Lactate - Lower lactate levels have been reported in overtrained athletes. This may indicate a reduction in the anaerobic glycolytic system (lactic acid) to produce energy or a decrease in buffering capacity of hydrogen ions from lactate release.
- Muscle Glycogen Depletion - It is possible that low glycogen stores can result from overtraining, not allowing the athlete to train intensely due to fatigue or lethargy.
- Blood Parameters - Blood measurements of urea, glucose, hemoglobin, ferritin, white blood cells and various liver enzymes and hormones. One hormone measurement that appears to mirror overtraining is a decrease in the ratio of free testosterone to cortisol. This could be due to changes in one or both.
- Creatine Phosphokinase (CPK) and Lactate Dehydrogenase (LDH) - When these enzymes are found in the blood, there is an indication that there may have been some damage to the cell membrane. While this has been reported from intense training, it is not necessarily a marker for overtraining. However, high levels of CPK in the blood may indicate that overtraining may be imminent.
- The Emerging Role of Glutamine as an Indicator of Exercise Stress and Overtraining, Rowbottom, D. G., Keast, D., & Morton, A. (1996), Sports Medicine. Feb: 21: (2) 80-97
Athletes at the elite level are always attempting to increase both the intensity and volume of training. If the training program creates an imbalance between intensity, volume and regeneration, a condition of overtraining can occur. An examination of specific parameters has been suggested to monitor overtraining.
The purpose of this study was to examine the role of the amino acid glutamine as a marker for monitoring overtraining.
Glutamine is one of the most versatile amino acids found in human muscle and plasma. Glutamine is maintained in the body at constant levels through its release by various tissues. The main role of glutamine includes the transfer of nitrogen between organs, detoxification of ammonia, regulating the acid-base balance during acidosis, fuel for gut cells, and cells of the immune system and protein synthesis.
Skeletal muscle glutamine accounts for more than 60 percent of the available amino acid pool. Animal studies reveal significantly higher levels of glutamine in type 1 rather than type 2 fibers. This indicates that skeletal muscle is a major organ of glutamine release into circulation and can provide adequate sources for other tissues. A depletion of glutamine has been reported to inhibit protein synthesis with the muscle.
During acidosis, ammonia is produced in the kidneys and excreted in the urine. Glutamine plays a significant role in the production of renal ammonia.
During a build up of lactate, demonstrated by an increase in hydrogen ions, the oxidation of glutamine by the kidneys increases bicarbonate ion production, assisting the buffering of these hydrogen ions. This indicates that the kidney is a major organ of glutamine production during acidosis.
Glutamine is an important fuel source for the immune system cells (macrophages, natural killer cells, lymphocytes) as well as cell replication. During periods of infection there is an increase in the production of glutamine to assist in cell division and protein synthesis, as well as wound healing. The increase in glutamine appears to come from the skeletal muscle into the plasma. Conversely, decreased plasma levels of glutamine may impair immune function.
The lungs can be an important source of glutamine, particularly during high levels of stress. The brain can also produce glutamine, altering perceived exertion, energy levels or lethargy. The liver appears to be an important source of maintaining plasma glutamine levels. The gastrointestinal tract has been reported as a major user of glutamine. It helps maintain the integrity of the gut, which fights bacterial invasion.
Glutamine and Exercise Stress
During prolonged exercise an increase in glutamine release from the muscles and the liver has been reported, increasing circulating levels within the plasma. At the completion of prolonged exercise, the plasma glutamine levels were reported to have dropped.
In high intensity exercise there is an increase in lactate production. With this lactate increase there is a concomitant increase in ammonia, which in turn, is excreted in the kidneys in the form of non-toxic glutamine. This can only be achieved by an increased release of glutamine from the muscle.
Plasma glutamine levels appear to be reduced significantly after both prolonged and intense exercise. Some researchers have suggested that it may take up to and beyond eight hours to replenish plasma glutamine levels. Further, it may be necessary for longer periods of recovery to ensure complete restoration to pre exercise levels.
During acute periods of overload training, it has been shown that plasma glutamine levels may take up to six days for complete restoration. Studies have suggested that after 10 days of overload training there can be up to a 50 percent reduction in plasma glutamine levels. It was also reported that a significant reduction in running performance accompanied this plasma glutamine decrease.
Glutamine and Overtraining
Overtraining is associated with prolonged periods of fatigue. There has been some evidence that an increased risk of infection may also accompany overtraining. This may be as a result of decreased plasma glutamine levels. More recent publications have drawn a correlation between sufferers of chronic fatigue syndrome and low levels of plasma glutamine. Some have even linked chronic fatigue syndrome in the normal population with overtraining in athletes.
While there is no direct supportive evidence that plasma glutamine decreases are related to susceptibility to infection, it cannot be ignored. In combination with immune depression, decreased plasma levels may impair the gastrointestinal tract to restrict bacterial and viral translocation, leading to diarrhea and other common overtraining complaints. It is in the interest of those in the overtraining state and others in overload training to consider manipulating their diet by increasing their glutamine intake, while only supplementing after careful consideration.
- Overtraining Following Intensified Training with Normal Muscle Glycogen, Snyder, A. C., Kuipers, H., Cheng, B., Servais, R., & Fransen, E. (1995), Medicine and Science in Sports and Science. 27 (7): 1063-1070
There is a fine line in enhancing performance. Drawing the line between doing too much and too little requires monitoring a number of overtraining markers to help maintain the program. Some markers suggested include delayed muscle glycogen resynthesis, reduced muscle glycogen levels, reduced caloric intake, reduced blood lactate levels, reduced exercising heart rate and increased resting heart rate.
Reduced muscle glycogen can adversely affect performance when exercising at between 65 to 85 percent of VO2max. Rarely do athletes consume enough carbohydrates to replenish the glycogen used. Consequently, overtraining can manifest itself through an initial decrease in glycogen resynthesis.
The purpose of this study was to determine if subjects who consumed enough carbohydrates during intense training could still become overtrained.
Eight competitive male cyclists who had been competing for least two years volunteered for this study. Subjects were monitored and tested during three training periods of seven days of long duration at moderate intensity, overtraining of 15 days of high intensity and recovery of minimal training for six days. Initial information collected included evaluating morning heart rate, hours of sleep, rating of perceived exertion during exercise etc.
Subjects were given 160g of liquid carbohydrate within the first two hours after the daily exercise bout. At two different times during the study, incremental tests to fatigue were administered.
The following criteria were used to determine if a subject was overtrained:
A reduced performance, reduced maximal heart rate of greater than 5 beats per minute, a reduced plasma cortisol level, a reduced maximal lactate rating of perceived exertion and a five question affirmative response from the daily questionnaire.
Dietary intake and carbohydrate percentage was not significantly different in the three training periods nor was resting muscle glycogen.
Application for the Fitness Instructor
- Even though all subjects were classified as overtrained by having satisfied three of the overtraining criteria, their muscle glycogen levels did not significantly reduce. In other words, they had normal muscle glycogen levels, yet were still overtrained. Given this, it could be said that reduced muscle glycogen levels may contribute to exercise induced fatigue, but is only one of many factors associated with overtraining.
- As part of identifying overtraining, all subjects demonstrated lower exercise heart rates at a range of different workloads. This has a relationship with oxygen uptake. At high intensity workloads, oxygen uptake was reduced during the overtraining period. However, during sub maximal levels of intensity, oxygen consumption did not differ. This difference was partly due to increases in stroke volume compensating for the reduced heart rate at sub maximal intensity levels. At high intensity levels, an increase in stroke volume was not possible to compensate a reduced heart rate.
- During the overtrained state, lactate levels at sub maximal workloads were lower. In previous studies it was proposed that this might have been a result of decreased glycogen levels. However, this was not the case in this study, where glycogen levels were normal, yet an overtrained state was still identified. Perhaps a more plausible explanation for the decreased lactate levels at sub maximal levels was a decreased sympathetic drive to the muscle.
- Plasma cortisol levels were lower for several days after the overtrained state. This is in agreement with other studies.
- The psychological well-being of subjects in this study deteriorated during the heavy training period. The recovery period of six days after the intense overtraining period was not long enough to reverse these effects. The researchers recommended between six and 10 to 20 days for psychological recovery.
- The rating of perceived exertion failed to show a relationship with overtraining. However, when RPE was expressed as a ratio to blood lactate, a more positive relationship occurred.