Overtraining syndrome

Geschatte leestijd: 9 minuten Overtraining, caused by excessive training combined with insufficient recovery time, results in muscle breakdown by increasing the activity of catabolic proteins and decreasing the activity of anabolic proteins. This is the outcome of a study to be published soon in the Journal of Strength & Conditioning Research (1).  

Strength training and recovery

The principles of muscle growth through training are familiar to most. Heavy resistance training causes small tears in the muscle fibers called microtrauma (2). During rest, these tears can heal, leading to muscle adaptation that results in additional muscle mass and strength (“adaptive microtrauma”) (2). When heavy training is accompanied by a lack of recovery time, microtrauma can turn into chronic and more severe forms of tissue damage, leading to injuries (3 ). This subsequently results in reduced strength (4) accompanied by significant muscle damage (5), swelling of the injured area, pain, edema (4,6), and local inflammation (7). When this occurs, recovery of the damaged muscle can take weeks or months of complete rest or a very limited training program.

Catabolism and anabolism ratio

Recently, I wrote about slow and fast protein (“whey is overrated”), but also in previous articles that (absolute) muscle growth results from muscle growth minus muscle breakdown (9). In muscles, protein can be synthesized from amino acids present in the bloodstream. These amino acids can come from ingested protein that is broken down into amino acids in the body. This process of protein synthesis in muscles is called protein synthesis. However, the body also has the ability to break down protein in muscles into amino acids and release them into the bloodstream as an energy source. This process is called proteolysis. Protein synthesis is an anabolic process. Anabolic means that the body uses available resources to build tissue. Proteolysis is a catabolic process. Catabolic means that tissue is broken down to provide energy. This can involve stored body fat being converted into glucose, but also protein in muscles being broken down into amino acids. These two processes, anabolic and catabolic, work simultaneously. A healthy 70kg man produces about 280 grams of new muscle mass per day, but also breaks down the same amount (7). The degree to which the body works catabolically and anabolically is called the catabolism/anabolism ratio (1).  Muscle growth occurs only when more protein is synthesized in muscles than broken down. This is called a positive protein balance (9).

Overtraining increases catabolism and muscle breakdown

Various studies have shown that overtraining increases the catabolism/anabolism ratio. This means that the ratio becomes more favorable to catabolism, and the body proportionally breaks down more than it builds up (10-13). In 2003, it was observed that overtrained individuals had more amino acids in the blood and less protein uptake from blood compared to well-trained individuals (11). The increased amount of amino acids in the blood was not due to higher intake of protein from food, but rather due to greater breakdown of protein in the muscles. Moreover, less protein was synthesized in muscles from amino acids in the blood. More breakdown and less building of muscle mass result in loss of muscle mass. Earlier research from 1999 showed that overtraining increases the catabolism/anabolism ratio in rats and thus decreases muscle mass (13). In that study, it was also found that the amount of DNA per muscle fiber decreased due to loss of muscle cell nuclei from muscle atrophy (loss of muscle mass). Also read the article: Overtraining, explanation of symptoms and recovery

Types of regulatory proteins

And this is where the most recent research continues. The researchers from Brazil wanted to know which processes are involved and thus how the catabolism/anabolism ratio is influenced (1). Before I continue, it might be good to explain that hormones and enzymes are also proteins, but with specific functions. Hormones are proteins that serve as messengers and can give certain cells commands. Testosterone is a well-known example of such a hormone that can instruct muscle cells, for example, to produce more protein (anabolic), while the hormone cortisol instructs them to break down protein (catabolic). Growth factors and enzymes are also proteins with specific functions. There are various such proteins that play a regulatory role in the amount of muscle mass, such as IGF-1 (insulin-like growth factor) and less-known proteins such as the so-called MRFs, myogenic regulatory factors (“myogenic” refers to “muscle tissue forming/originating from muscle tissue”) MyoD, Myf-5, myogenin, and MRF4 (14). IGF-1 is considered one of the most important factors in muscle mass formation (15-17), but the MRFs also play a significant role in this (14,18). In contrast, there are enzymes that work catabolically, such as those belonging to the family of E3 ubiquitin ligases. One of the enzymes in this family, MAFbx, is known for its significant contribution to proteolysis (as explained earlier, the breakdown of proteins into amino acids) (19,20). For example, when nerves to a muscle are cut, leading to paralysis and muscle atrophy, the activity (protein expression) of this enzyme is found to be increased (19). The Brazilian researchers suspected that the activity of the anabolically working IGF-1 and MRFs is decreased by overtraining and lack of recovery, while the catabolically working MAFbx becomes more active as a result.

Research on muscle breakdown in rats

To test this theory, the Brazilians overtrained nine rats in a way that would not please the Party for the Animals. Rats were chosen instead of humans because studies on humans can be inadvertently influenced by factors such as motivation, nutrition, and lifestyle (1). The training program lasted twelve weeks, during which the rats were overloaded by 15% compared to the previously calculated optimal load for positive muscle adaptation in rats (21). In these twelve weeks, training was conducted for five consecutive days each week to avoid sufficient recovery time. Another group of nine rats did not follow a training schedule and served as a control group. The group that trained performed a “water jump exercise”. In the image on the right, you can see how this was done. The rats were fitted with weighted vests and placed in a container with 38 cm of water. This was about 150% of the length of the rats, who could not swim due to the weight of the vest and thus sank to the bottom. To avoid drowning, the rats had no choice but to jump to the water surface to breathe, after which they sank back down. Each jump counted as one repetition. First, a week of “pre-training” was conducted to acclimate the rats. After this, the 12-week schedule began, with the load increasing each time (a heavier vest), which, in combination with lack of recovery, has been shown to lead to muscle atrophy. Two days after the last training session, the rats were anesthetized and decapitated (sorry Mrs. Thieme). Immediately thereafter, the middle (the muscle belly) of the plantaris muscle was removed and frozen (see image on the right for location of plantaris). The frozen plantaris muscles were used to measure the so-called morphometry. “Morphometric research aims to record characteristics of tissue architecture … and individual cell characteristics (such as cell size, nucleus size, nucleus shape, nucleus orientation) in size and number” (22). In this case, it involved measuring the muscle fibers and the area of the muscle’s cross-section (CSA, cross-sectional area). However, the main measurements concerned the protein expression, the influence on the aforementioned regulatory proteins. The trained rats had a lower body weight after twelve weeks than the rats that did not train, while the diet was the same (the rats had unlimited access to rat food). This indicates a decrease in muscle mass and/or body fat. To distinguish between the two, the size of the muscle (CSA) was examined. The researchers observed that it was significantly smaller in the group that trained, indicating muscle atrophy Protein expression results:  Subsequently, protein expression was examined. Protein expression is the way these proteins do their job (translation). For simplicity, this can be seen as the degree of influence of the proteins. This is not entirely correct, but makes it easier to understand. After all, we ultimately only want to know if the catabolic proteins have had a greater effect and the anabolic proteins have had a smaller effect. This indeed turned out to be the case. The expression of the anabolic proteins IGF-1, MyoD, and myogenin was lower than in the group that did not train. For IGF-1, this was even 43% lower, for MyoD 27%, and myogenin 29%. However, the expression of the catabolic protein MAFbx was 20% greater than in the group that did not train.

Conclusion

Most people know that overtraining is not good. However, this is usually thought of in terms of the risk of injuries and limited or completely inhibited muscle growth. With this latest research, it has once again been demonstrated that overtraining actually results in depletion of your body. The effect of the important muscle-building growth factor IGF-1 and other myogenic regulatory factors is significantly reduced by overtraining and lack of recovery time. At the same time, the effect of muscle-degrading proteins, such as the enzyme MAFbx, is increased. This means that overtraining has a counterproductive effect on your training goals. I can’t think of a better reason to ensure an adequate recovery time. What’s the point of training 6 to 7 days a week and training each muscle group multiple times a week if it actually results in less muscle mass (and thus more body fat storage because the body burns fewer calories) and possible injuries that prevent you from training for weeks? The training split, the distribution of the muscle groups you train and the rest in between, therefore remains one of the most important factors when it comes to muscle growth. Of course, nutrition plays a major role as a supplier of energy in the form of carbohydrates and fats and building blocks from protein. However, apparently the body does not send a signal to eat more when it is overtrained, as evidenced by the fact that the rats that trained ate just as much as the rats that did not train. It is also questionable to what extent nutrition can have a limiting effect on the effects of overtraining that go far beyond the effects of a negative mismatch between the need for energy and building blocks and what is actually eaten (undernutrition). This latter situation occurs regularly, leading to decreased or absent muscle growth. The effects of overtraining go beyond that and as it were provide a different setting of important regulatory proteins that additional nutrition is unlikely to change much. Jay Cutler’s statement that “there is no such thing as overtraining, only undernutrition” therefore does not apply in my opinion. But the first time I heard that statement, I assumed it was deliberately stated in such an unnuanced way to emphasize the importance of nutrition. So make sure you have a good schedule with enough rest, but also pay attention to signs of overtraining such as the mentioned swelling, inflammation, and pains to be able to react in time.

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