The Role of Tissue Trauma and Cytokines in Overtraining:
A friend asked me a few days ago, "How would it be possible to be overtrained more than once in your athletic career? Wouldn't an athlete have learned something the first time?" The best answer I have to this question is that even if you've been overtrained before, you can get overtrained again if you are feeling outside pressure to ignore the signals you are getting from your own body.
From some of the things I've heard lately, I am not convinced that all of the people around me know all there is to know about overtraining: How it comes about, how the signs manifest themselves, and how to prevent it from doing too much damage to one's season. Listen to the following quotes from various people who will remain nameless...
1. "It is impossible to get overtrained from doing workouts that only stress the muscles. The only way to get overtrained is by over-stressing the cardiovascular system."
2. "I've never heard of tiredness leading to an inability to focus on the ice."
3. "How can you be depressed if you're doing something you love?"
4. "It's a pleasure to watch you skate. I just don't like to look at your face."
After hearing enough of these misconceptions, I decided that some of the people I love dearly need a lesson in physiology. Fortunately, my teammate Lyle McDonald, a nutritionist and physiologist, was willing to provide me with some relevant scientific literature.
In this post, I will summarize what I learned from the following articles by Dr. Lucille Lakier Smith:
Cytokine hypothesis of overtraining: a physiological adaptation to excessive stress? Med. Sci. Sports Exerc., Vol. 32, No. 2, pp. 317-331, 2000.
Tissue Trauma: The Underlying Cause of Overtraining Syndrome? J. Strength Cond. Res. 18(1): 184-191. 2004
Overtraining syndrome (OTS) is a condition that occurs when an athlete trains intensely and under a heavy load, but performance deteriorates. Overtraining can be distinguished from "overreaching," which is a necessary training-induced stress given to the body in order to cause adaptation, by the duration of recovery. Whereas the overreached athlete recovers within a few days of rest, the overtrained athlete can take 6 weeks or more to recover.
Though there have been several different theories proposed to account for OTS, most of these only account for a few specific symptoms. For example, the glycogen hypothesis suggests that under a heavy training load, the athlete is unable to consume enough calories to maintain muscle glycogen stores, leading to feelings of "heavy legs" and fatigue. The glutamine hypothesis, on the other hand, suggests that the reduced level of blood glutamine observed in OTS leads to a suppression of the immune system.
An all encompassing hypothesis that could explain the origins of these and several other symptoms of OTS is proposed by Dr. Smith: "The present hypothesis proposes that trauma to the muscular, skeletal, and/or joint system, is frequently the initiator of OTS."
It is known that training causes microtrauma to the athlete's muscle and connective tissue. If the volume and intensity of training is too high, and the rest is not enough for the athlete to have an appropriate recovery, then it is possible for the athlete to develop a chronic, severe form of tissue trauma and inflammation. There seems to be a great deal of evidence pointing towards this tissue trauma as the driving force behind overtraining syndrome.
The theory is that local tissue damage to muscles (from training) leads to local acute inflammation, which can develop into chronic inflammation if the athlete is not given sufficient rest. This chronic local inflammation may lead to an activation of the body's systemic immune/inflammatory response. And this is where those cytokines come in.
"Cytokines may be defined as soluble hormone-like proteins." They are the molecules by which cells "communicate" with each other. They are activated by stimuli such as free radicals, tissue injury, and infectious agents (viruses, etc). Cytokines are involved in the inflammatory response.
It is proposed that chronic inflammation from the tissue damage caused by excessive training leads to elevated levels of circulating cytokines, which interact with various systems of the body in ways that explain several of the symptoms of OTS.
"One of the first signs of OTS is a change in mood and behavior. The athlete may be transformed from an outgoing, enthusiastic, sociable, highly competitive individual, to being constantly tired, depressed, and uninterested in training and competing, and possibly angry and hostile. Frequently, changes in mood and behavior are evident before the drop in performance..." (which can explain why "she is still skating well even though she has a miserable scowl on her face.")
A growing body of evidence suggests that an overtrained athlete's antisocial and depressed behavior may be induced by increased levels of the proinflammatory cytokines IL-1B, IL-6, and TNF-a. It is thought that these cytokines are meant to induce behavioral changes that are conducive to rest and recovery, as is illustrated by "Hart's description of how a sick or injured animal behaves in the wild, in order to increase its chance for recovery. The wounded animal becomes lethargic (akin to human depression), loses its appetite, has a reduced libido, and is less sociable. All these factors encourage rest and protect it from exposure to predators, thus increasing its factors of survival."
Cytokines have been shown to act on several areas of the brain, and have been particularly closely linked to depression and an inability to concentrate. In addition to their action on the brain, cytokines have also been shown to alter levels of circulating hormones, such as cortisol and testosterone.
Another process in which cytokines are involved is the synthesis of acute phase proteins. In a situation of chronic injury, cytokines act on the liver to induce the production of these "recovery proteins." This new protein synthesis leads to the uptake of amino acids from the blood (because amino acids are the building blocks of proteins.) This could account for the reduction of levels of certain amino acids in the blood, as well as mineral depletion (because minerals such as zinc and magnesium are enzyme cofactors used by the "molecule producing factories").
This leaves us with the question of immune suppression: Why is an overtrained athlete more likely to get sick?
There are two arms of the adaptive immune system: The cell-mediated system, which deals with intracellular invaders, such as bacteria and viruses; and the humoral system, which deals with the elimination of pathogens that exist outside the cells -- in the blood or other extracellular fluid media of the body.
The latest perspective on the function of adaptive immunity is that while one arm of the adaptive system is activated, the other branch is deliberately suppressed. Therefore, since the pro-inflammatory cytokines released during a condition of chronic inflammation are involved in humoral immunity, the overtrained athlete's cell-mediated immunity becomes suppressed, resulting in an increased susceptibility to bacterial and viral infection.
Now I will list several easily observable signs and symptoms associated with OTS (from Table 1 of the 2004 paper)
Performance parameters:
decreased performance
inability to meet previous standards
prolonged recovery
reduced toleration of loading
decreased muscular strength
decreased maximum work capacity
Psychological/behavioral:
constant fatigue
reduced appetite
change in sleep patterns
depression
general apathy
decreased self esteem
emotional instability
fear of competition
easily distracted
gives up when the going gets tough
Information processing:
loss of coordination
reappearance of previously corrected mistakes
difficulty in concentrating
decreased capacity to deal with large amounts of information
reduced capacity to correct technical faults
Immunological parameters:
constant fatigue
complaints of muscle and joint aches and pains
headaches
nausea
gastrointestinal disturbances
increased aches and pains
muscle soreness/tenderness
increased susceptibility to and severity of colds, allergies, etc.
bacterial infections
one-day colds
swelling of lymph glands
In light of all this new information, I'd make the following responses to the quotes with which I began this post:
1. "It is impossible to get overtrained from workouts that only stress the muscles. The only way to get overtrained is by stressing the cardiovascular system."
Not only is it possible to get overtrained from doing work that only stresses the muscles, but the most current, all-encompassing theory of overtraining is based on local muscle/tissue damage as the driving force for the inflammatory process that can result in all of the symptoms seen in overtraining.
2. "I've never heard of tiredness leading to an inability to focus on the ice."
This one can be answered by looking at the table of signs and symptoms, under the section entitled "information processing." There it is in black and white: One of the signs of overtraining is "difficulty in concentrating."
3. "How can you be depressed if you're doing something you love?"
If speedskating is "something you love" and you do too much of it, then it is biochemically possible to get depressed doing something you love. Once again, the cytokines released in overtrained athletes have been strongly linked to depression.
4. "It's a pleasure to watch you skate. I just don't like to look at your face."
Word-for-word, from the 2004 paper: "Frequently, changes in mood and behavior are evident before the drop in performance, but as long as the athlete is performing well, these factors may be ignored." Remember: BY THE TIME HER SKATING MATCHES THE LOOK ON HER FACE, IT MAY ALREADY BE TOO LATE.
A friend asked me a few days ago, "How would it be possible to be overtrained more than once in your athletic career? Wouldn't an athlete have learned something the first time?" The best answer I have to this question is that even if you've been overtrained before, you can get overtrained again if you are feeling outside pressure to ignore the signals you are getting from your own body.
From some of the things I've heard lately, I am not convinced that all of the people around me know all there is to know about overtraining: How it comes about, how the signs manifest themselves, and how to prevent it from doing too much damage to one's season. Listen to the following quotes from various people who will remain nameless...
1. "It is impossible to get overtrained from doing workouts that only stress the muscles. The only way to get overtrained is by over-stressing the cardiovascular system."
2. "I've never heard of tiredness leading to an inability to focus on the ice."
3. "How can you be depressed if you're doing something you love?"
4. "It's a pleasure to watch you skate. I just don't like to look at your face."
After hearing enough of these misconceptions, I decided that some of the people I love dearly need a lesson in physiology. Fortunately, my teammate Lyle McDonald, a nutritionist and physiologist, was willing to provide me with some relevant scientific literature.
In this post, I will summarize what I learned from the following articles by Dr. Lucille Lakier Smith:
Cytokine hypothesis of overtraining: a physiological adaptation to excessive stress? Med. Sci. Sports Exerc., Vol. 32, No. 2, pp. 317-331, 2000.
Tissue Trauma: The Underlying Cause of Overtraining Syndrome? J. Strength Cond. Res. 18(1): 184-191. 2004
Overtraining syndrome (OTS) is a condition that occurs when an athlete trains intensely and under a heavy load, but performance deteriorates. Overtraining can be distinguished from "overreaching," which is a necessary training-induced stress given to the body in order to cause adaptation, by the duration of recovery. Whereas the overreached athlete recovers within a few days of rest, the overtrained athlete can take 6 weeks or more to recover.
Though there have been several different theories proposed to account for OTS, most of these only account for a few specific symptoms. For example, the glycogen hypothesis suggests that under a heavy training load, the athlete is unable to consume enough calories to maintain muscle glycogen stores, leading to feelings of "heavy legs" and fatigue. The glutamine hypothesis, on the other hand, suggests that the reduced level of blood glutamine observed in OTS leads to a suppression of the immune system.
An all encompassing hypothesis that could explain the origins of these and several other symptoms of OTS is proposed by Dr. Smith: "The present hypothesis proposes that trauma to the muscular, skeletal, and/or joint system, is frequently the initiator of OTS."
It is known that training causes microtrauma to the athlete's muscle and connective tissue. If the volume and intensity of training is too high, and the rest is not enough for the athlete to have an appropriate recovery, then it is possible for the athlete to develop a chronic, severe form of tissue trauma and inflammation. There seems to be a great deal of evidence pointing towards this tissue trauma as the driving force behind overtraining syndrome.
The theory is that local tissue damage to muscles (from training) leads to local acute inflammation, which can develop into chronic inflammation if the athlete is not given sufficient rest. This chronic local inflammation may lead to an activation of the body's systemic immune/inflammatory response. And this is where those cytokines come in.
"Cytokines may be defined as soluble hormone-like proteins." They are the molecules by which cells "communicate" with each other. They are activated by stimuli such as free radicals, tissue injury, and infectious agents (viruses, etc). Cytokines are involved in the inflammatory response.
It is proposed that chronic inflammation from the tissue damage caused by excessive training leads to elevated levels of circulating cytokines, which interact with various systems of the body in ways that explain several of the symptoms of OTS.
"One of the first signs of OTS is a change in mood and behavior. The athlete may be transformed from an outgoing, enthusiastic, sociable, highly competitive individual, to being constantly tired, depressed, and uninterested in training and competing, and possibly angry and hostile. Frequently, changes in mood and behavior are evident before the drop in performance..." (which can explain why "she is still skating well even though she has a miserable scowl on her face.")
A growing body of evidence suggests that an overtrained athlete's antisocial and depressed behavior may be induced by increased levels of the proinflammatory cytokines IL-1B, IL-6, and TNF-a. It is thought that these cytokines are meant to induce behavioral changes that are conducive to rest and recovery, as is illustrated by "Hart's description of how a sick or injured animal behaves in the wild, in order to increase its chance for recovery. The wounded animal becomes lethargic (akin to human depression), loses its appetite, has a reduced libido, and is less sociable. All these factors encourage rest and protect it from exposure to predators, thus increasing its factors of survival."
Cytokines have been shown to act on several areas of the brain, and have been particularly closely linked to depression and an inability to concentrate. In addition to their action on the brain, cytokines have also been shown to alter levels of circulating hormones, such as cortisol and testosterone.
Another process in which cytokines are involved is the synthesis of acute phase proteins. In a situation of chronic injury, cytokines act on the liver to induce the production of these "recovery proteins." This new protein synthesis leads to the uptake of amino acids from the blood (because amino acids are the building blocks of proteins.) This could account for the reduction of levels of certain amino acids in the blood, as well as mineral depletion (because minerals such as zinc and magnesium are enzyme cofactors used by the "molecule producing factories").
This leaves us with the question of immune suppression: Why is an overtrained athlete more likely to get sick?
There are two arms of the adaptive immune system: The cell-mediated system, which deals with intracellular invaders, such as bacteria and viruses; and the humoral system, which deals with the elimination of pathogens that exist outside the cells -- in the blood or other extracellular fluid media of the body.
The latest perspective on the function of adaptive immunity is that while one arm of the adaptive system is activated, the other branch is deliberately suppressed. Therefore, since the pro-inflammatory cytokines released during a condition of chronic inflammation are involved in humoral immunity, the overtrained athlete's cell-mediated immunity becomes suppressed, resulting in an increased susceptibility to bacterial and viral infection.
Now I will list several easily observable signs and symptoms associated with OTS (from Table 1 of the 2004 paper)
Performance parameters:
decreased performance
inability to meet previous standards
prolonged recovery
reduced toleration of loading
decreased muscular strength
decreased maximum work capacity
Psychological/behavioral:
constant fatigue
reduced appetite
change in sleep patterns
depression
general apathy
decreased self esteem
emotional instability
fear of competition
easily distracted
gives up when the going gets tough
Information processing:
loss of coordination
reappearance of previously corrected mistakes
difficulty in concentrating
decreased capacity to deal with large amounts of information
reduced capacity to correct technical faults
Immunological parameters:
constant fatigue
complaints of muscle and joint aches and pains
headaches
nausea
gastrointestinal disturbances
increased aches and pains
muscle soreness/tenderness
increased susceptibility to and severity of colds, allergies, etc.
bacterial infections
one-day colds
swelling of lymph glands
In light of all this new information, I'd make the following responses to the quotes with which I began this post:
1. "It is impossible to get overtrained from workouts that only stress the muscles. The only way to get overtrained is by stressing the cardiovascular system."
Not only is it possible to get overtrained from doing work that only stresses the muscles, but the most current, all-encompassing theory of overtraining is based on local muscle/tissue damage as the driving force for the inflammatory process that can result in all of the symptoms seen in overtraining.
2. "I've never heard of tiredness leading to an inability to focus on the ice."
This one can be answered by looking at the table of signs and symptoms, under the section entitled "information processing." There it is in black and white: One of the signs of overtraining is "difficulty in concentrating."
3. "How can you be depressed if you're doing something you love?"
If speedskating is "something you love" and you do too much of it, then it is biochemically possible to get depressed doing something you love. Once again, the cytokines released in overtrained athletes have been strongly linked to depression.
4. "It's a pleasure to watch you skate. I just don't like to look at your face."
Word-for-word, from the 2004 paper: "Frequently, changes in mood and behavior are evident before the drop in performance, but as long as the athlete is performing well, these factors may be ignored." Remember: BY THE TIME HER SKATING MATCHES THE LOOK ON HER FACE, IT MAY ALREADY BE TOO LATE.
posted by Eva at 12:25 PM
<< Home