Often athletes striving to become faster and better at their sport find themselves walking the tightrope of overtraining. During peak training times, most athletes feel fatigue, as their training plans are intended to create a similar fatigue that will be experienced on race day. Coaches do their best to create a perfect, personalized plan without overtraining or injury. Sometimes, even a perfectly planned training schedule can lead to overtraining, or athletes will push harder and go farther than the plan laid out for them in attempts to gain even more improvements.
There are several hypotheses behind why overtraining syndrome (OTS) occurs. This week, I decided to feature the research article “Overtraining Syndrome”. In the article, several possible causes for OTS were identified. I have summarized the main hypotheses as well as provided application below.
- Deficit glycogen levels in muscles – muscles use glycogen to perform; when there is a low level of glycogen in the muscles oxidation increases and branch chain amino acid (BCAAs) levels reduce resulting in fatigue and may cause OTS.
Practical Application: Ensure carbohydrates are a part of your daily intake. While there are general recommendations for carbs (40-60% of total intake) your bodies needs will be depended on the type of training you are participating in, event distance/time as well as personal metabolic rate. Sources include: fruit, grains, starchy vegetables, milk, yogurt, beans.
- Elevated serotonin levels – unbound tryptophan and BCAAs use the same door to be absorbed into the brain. As we are active, BCAAs are oxidized, which in turn allows tryptophan to enter into the brain and be converted to serotonin. Excessive exercise has been linked to higher levels of serotonin and its precursors which can result in higher levels of fatigue and depression. In a well-trained athlete, most of the time they are less sensitive to higher levels of serotonin, but in the case of OTS athletes seem to be more susceptible.
Practical Application: First off, follow your training plan from your coach and be open with them on how you are feeling. Talk to them about how recovery is going and if you think training level or intensity needs to be decreased for the week, listen to your body and address it with your coach. Second, it is important asses your ability to manage emotions. If it seems you are on an emotional roller-coaster, it may be due to OTS and you need to rest. Third, sleep is incredibly important! Aim for 7-8 hours of sleep.
- Insufficient levels of glutamine – exercise bouts greater than 2 hours or reoccurring high-intensity training can lower the levels of glutamine. Low levels of glutamine may contribute higher susceptibility of upper respiratory tract infections.
Practical Application: Ensure your diet includes daily intake of glutamine. Sources can be found in plant and animal products: raw spinach and parsley, cabbage, beef, poultry, pork, dairy (milk, ricotta cheese, yogurt and cottage cheese).
- Oxidative Stress – A certain level of oxidative stress is expected and even desired for cellular repair. However, when oxidative stress is elevated above optimal levels, inflammation, muscle soreness and fatigue occur.
Practical Application: Elevated oxidative stress can have negative effects on performance. Unfortunately, the research in this area is limited and more research is needed.
- Autonomic Nervous System – The autonomic nervous system (ANS) is the system responsible for functions that are unconsciously controlled such as breathing, digestion and heartbeat. This system is also the one that controls our fight-or-flight response. An imbalance of the ANS can result in fatigue, bradycardia, and depression or performance inhibition.
Practical Application: A week of rest may restore the imbalance in the ANS but research is not completely clear for this hypothesis.
- Hypothalamic Alteration – The hypothalamus helps regulate weight, body temperature, emotions, appetite, salt/water balance, sex drive, memory, sleep-wake cycle as well as our body clock. The pituitary gland is also controlled by the hypothalamus. The pituitary gland regulates the ovaries, testes, adrenal glands and the thyroid. Overtrained athletes may see/feel alterations in hormone levels such as cortisol, testosterone and adrenocorticotropic hormones. Adrenocorticotropic hormone is responsible for the production and release of cortisol. The level of negative impact OTS has on the hypothalamic function is individualized and may depend on exercise volume and other stressors in the athlete’s life.
Practical Application: Results from stress on the hypothalamus varies athlete by athlete. If overtrained, not only is performance impacted but sex drive/hormone production as well as ability to get pregnant may also be reduced. If you are noticing any changes in the functions listed above, get blood work done to see if hormones are out of normal range. Results may help you determine if you are suffering from OTS and take action and allow the hypothalamus to recover and function appropriately.
- Cytokine Hypothesis – Cytokines are proteins that assist with communications between cells in our body. There are both pro-inflammatory and anti-inflammatory cytokines. When an athlete is training, it is normal to have local acute microtrauma to the tissue as a result of muscle contraction and repetitive joint action. Adaptations occur from the microtrauma; tissues will naturally recover and strengthen with the help of cytokines over time and with adequate rest. If intense training occurs without the necessary recovery time, inflammatory responses from the microtrauma increase and the inflammation becomes local and chronic. Elevated levels of cytokines may impact the brain in overtrained athletes and as a result there may be mood changes and depression experienced.
Practical Application: Athletes will naturally have inflammation in their bodies due to training and volume. The body is capable of managing inflammation with cytokines as long as there is adequate rest and recovery time. If mood swings are occurring and you are finding it hard to manage your emotions, it may be due altered levels of cytokines and OTS.
Bottom Line: No single hypothesis discussed can be determined as the ONLY cause of OTS. More than likely, if an athlete is overtrained, it is due to a combination of causes. If you are having signs and symptoms of OTS, talk to your coach and maybe even see your physician for blood work, don’t just “suffer” through the pain and fatigue. It is always better to scale training back so that you can go into the season/event at your best rather than push through the fatigue and risk long term effects of OTS.