How Looking Inside Helps You Deal with Overtraining

By Neel Duggal, December 31, 2015


Are you a marathon runner feeling more fatigued than usual? A crossfit pro putting more effort into your strength training but not getting the results you want? An active person suddenly feeling under the weather after your workouts? If so, you might be suffering from overtraining syndrome (OTS).

When we think of OTS, our first instinct is to tell the “overtrainee” to either rest or stop complaining. However, biomarkers in your blood paint an intricate picture of the sources of overtraining that allow you to prevent and treat it much more effectively. In this article, we document how you can use blood analytics to determine if you’re overtraining and offer some actionable recommendations to get back to peak performance and health.

The Essentials: What is Overtraining?

Never-ending fatigue. Burnout. Hitting a wall. Staleness. These describe the frustrating situation in which you ramp up your training to get better results, but wind up feeling weaker and more tired than before. Scientists define OTS as “a maladapted response to excessive exercise without adequate rest, resulting in perturbations of multiple body systems (neurologic, endocrinologic, immunologic) coupled with mood changes.” [1] In layman’s terms, OTS occurs when a training schedule increases dramatically or suddenly without allowing sufficient recovery and proper dietary adjustments. The result typically is a decline in performance and health.

An estimated 15% of professional athletes suffer from OTS in one season alone, and it can take several weeks or even months for them to get back to peak performance. [2]

Many athletes and non-athletes alike frequently experience symptoms associated with OTS. Some of the most common include:

  • Chronic fatigue
  • Increased risk of injury in the skeletal, muscular, and nervous systems
  • Muscle soreness and tenderness
  • Prolonged recovery from exercise
  • Impaired muscular strength
  • Increased anxiety

How Is Your Training Affecting You?

Preventing, detecting, and successfully treating OTS is of paramount importance to both elite and recreational athletes. Continuous periods of fatigue can hamper preparation for major sports events, resulting in poor performance that can even derail an athlete’s career. OTS can undo the health benefits associated with exercise and increase the risk of such illnesses as cardiovascular disease, depression, and type II diabetes. In addition, OTS can result in overall feelings of unhappiness, creating long-term health problems for overtrained athletes and non-athletes alike.

Historically, the approach to treating OTS has been saying “take rest and recover” or “stop whining and get over it.” However, recent research has unveiled an association between many symptoms of overtraining and levels of certain biomarkers—key chemical substances in the blood you can modify through lifestyle interventions. Below we document research showing how five biomarkers—testosterone, sex hormone-binding globulin (SHBG), cortisol, c-reactive protein (CRP), and creatine kinase (CK)—explain problems associated with overtraining. In each case we provide research-backed interventions to prevent and treat these concerns.

No more muscle growth? Test your testosterone

The hormone testosterone is synonymous with manliness. It develops male characteristics such as facial hair and deep voices. Testosterone is also a key indicator of health and fitness in both men and women. As an anabolic hormone, it regulates muscle growth, maintenance of bone strength, and libido.

Because testosterone is important for growth and recovery, low levels of free testosterone may indicate that you are not getting sufficient rest, and might also result in a decline in muscle growth and general health. In a 2004 study, exercise physiologists monitored the performance of 25 elite rugby players during February, the month of their most intense training and competition. The subjects trained for 15 hours and participated in one match each week.

On each rest day, the players filled out a questionnaire from the French Society of Sports Medicine with 54 “yes” or “no” questions related to symptoms associated with overtraining. Additionally, the subjects provided three saliva samples (at 8 am, 11 am, and 5 pm) on rest days, and researchers assessed the samples for levels of testosterone. They noticed a strong negative correlation between increased numbers of overtraining symptoms and testosterone levels. They concluded that “testosterone concentration is influenced by tiredness and is, therefore, a valid marker of tiredness.” [3]


If your blood analysis shows low levels of testosterone due to overtraining, it is crucial to get sufficient rest and recovery. Additionally, your blood analysis can suggest a variety of ways to increase testosterone. Some research indicates that magnesium deficiency may decrease testosterone production. If your tests show low levels of magnesium, you can get back into optimal zones by consuming dark green leafy vegetables, pumpkin seeds, nuts, cocoa, and seafood. 

Key Takeaway: Overtraining can result in low levels of testosterone. This is problematic for athletic performance, muscular growth, and general health.

Recommendation: Make sure you get adequate rest and recovery to increase testosterone. Additionally, if you are deficient in other biomarkers such as magnesium and zinc, consider modifying your diet to correct these deficiencies.

Worried about injury? Check your sex-hormone binding globulin (SHBG) levels

Sex Hormone-Binding Globulin (SHBG) is a protein produced by the liver. It binds to sex hormones, such as testosterone and estrogen, and transports them throughout the bloodstream. Much of the body’s testosterone is bound to SHBG. When testosterone attaches to SHBG, it is inactive and does not exert its typical effects such as increased muscle recovery. Scientists refer to the sum of SHBG-bound testosterone and free testosterone as “total testosterone” (TT).

Elevated levels of SHBG may indicate overtraining and lead to poorer athletic performance and health, as it inactivates Testosterone. In a 2011 study, Finnish scientists enlisted 57 males with an average age of 20 and had them undergo eight weeks of increasingly strenuous military training in relatively cold temperatures (13.6 Celsius, or 56.5F). In week one, the physical regimen started with 2 hours/day; by week eight, they were training 8 hours per day.

This was the first experience for many subjects in demanding physical training, performing overnight exercises in a forest, and eating outdoors. As a result, researchers surmised that they would experience symptoms associated with OTS such as a sudden performance decline. At weeks 1, 4, and 7, the researchers extracted blood samples from the subjects after 12 hours of fasting and assessed them for SHBG and TT. While TT levels remained the same each time, SHBG levels increased between weeks 4 and 7. Noting the increase in SHBG without a corresponding increase in TT, researchers concluded that overtraining can lead to increased injury risk and lower muscle recovery as there is less available, active Testosterone. [4]

What if your InsideTracker assessment reveals elevated levels of SHBG? A research-proven intervention will lower those levels. According to one study, “long-term, severe calorie restriction reduces serum total and free testosterone and increases SHBG concentration in human, independently of adiposity.” [5] Thus, if you have below optimal levels of SHBG, make sure that you are getting enough healthy calories in your diet.

Key Takeaway: Elevated levels of SHBG lower levels of free, active testosterone. This may increase the risk of injury and decrease the extent of muscle recovery.

Recommendation: If your blood analysis shows increased levels of SHBG, evaluate your caloric intake.

Experiencing inflammation? Check your C-reactive protein (CRP)

C-reactive protein (CRP) is produced by the liver and released into the bloodstream within a few hours after inflammation resulting from tissue injury or infection by a foreign cell. Consistently elevated levels of CRP can lead to depression and a variety of cardiovascular illnesses. [6, 7]

Considerable research shows that regular exercise with proper recovery leads to long-term decreases in levels of CRP. [8] However, OTS and insufficient recovery can undo the beneficial effects of exercise on lowering inflammation and CRP. In a 2006 study, researchers recruited 17 recreationally trained men and had them participate in 8 resistance multi-joint exercises, such as bench presses and squats, during four training periods. The first training period consisted of low-intensity exercise, the second high-intensity resistance training, the third period high-intensity resistance training, and the fourth low-intensity resistance training.


After the second training period, CRP increased by 300% compared to baseline levels. After the third period, CRP increased by 400% compared to baseline levels. [9] These findings suggest that high-intensity training increases inflammation and temporarily results in increased CRP. If you do not get sufficient recovery, CRP levels will remain elevated. It is important to make sure that you have completed your exercise within the last 24 hours when you are getting a CRP test.

While there isn’t a lot research on dietary and lifestyle interventions that directly lower CRP, a couple of interventions show promise. In a five-day, randomized crossover study, researchers assessed the impact of green tea and cocoa beverages on indicators of aging including CRP. Both green tea and cocoa foods contain a set of compounds called “flavanols.” Researchers provided 20 adults with controlled diets and had one group consume four cocoa beverages containing 30-900 mg of cocoa flavanols per day and the other group consume four beverages of tea per day containing 30-900 mg of green tea flavanols. At the end of the study, scientists observed that as subjects consumed higher doses of cocoa flavanols, their levels of CRP decreased. [10] In contrast, green tea flavanols did not influence levels of CRP in the blood. [10]

In another study, researchers provided 33 healthy adults (14 women, 19 men) with two different diets each for two weeks. The first diet, called the HT diet, contained high levels of antioxidants. The second diet, called the LT diet, contained lower levels of antioxidants. After each diet was completed, the scientists measured CRP levels in the subjects’ blood.  At the end of the study, the researchers noted that the subjects’ LT and HT diets did not different significantly in macronutrients, fruit and vegetable consumption, or dietary fiber intake. However, they observed that the subjects experienced lower levels of CRP after consuming the antioxidant-rich HT diet compared to the antioxidant-deficient LT diet. [11] In order to reduce CRP, we recommend eating a diet containing foods high in antioxidants such as our focus food raspberries.

Key Takeaway: CRP is a strong indicator of inflammation resulting from tissue injury associated with OTS and poor recovery. If you have consistently high levels of CRP, you might put yourself at increased risk for cardiovascular disease and mental illness.

Recommendation: If you have elevated levels of CRP, consider adding unsweetened, natural cocoa to your diet or supplements of cocoa flavanols or flavonoids. Additionally, eating a diet rich in antioxidants can help lower levels of CRP.

Feeling fatigued? Control your Cortisol

Frequently dubbed the “stress hormone,” cortisol serves many key functions. It breaks down tissues to give you energy for that big race, upcoming athletic event, or everyday activities such as running from a grizzly bear. It also prevents an overactive immune system and increases blood sugar if it’s too low. Nonetheless, unhealthily elevated levels of cortisol are indicative of overtraining and can lead to constant fatigue, a weakened immune system, and chronic stress. Additionally, long-term elevation of cortisol can increase your risk of developing depression and metabolic syndrome. [12, 13]


Cortisol is associated with fatigue resulting from overtraining. In a 2011 study, sports physiologists recruited 13 elite semi-endurance male athletes with an average age of 19 for a 14-week study. They participated in morning and afternoon running sessions and researchers collected blood samples during three phases of training to measure cortisol. The first phase was the before-preparation phase, the second was the after-preparation phase, and the third was the before-competition phase when training and stress were at their maximum. The authors discovered that cortisol levels were highest before a competition. They concluded that “long and intensive exercises weaken the immune system while moderate and short drills strengthened this system.” [14]

In another high-quality study, sports physiologists examined the effects of overtraining in 14 female college swimmers. Researchers tracked the swimmers in September where they swam a moderately intense 2,000 yards/day (baseline), in January where they progressed to a peak of 12,000 yards/day (overtraining conditions), and in February where they only swam 4,500 yards/day. Their moods, as measured by a Profile of Mood States questionnaire, showed significant increases in symptoms associated with overtraining such as anxiety, anger, fatigue, and depression.

Researchers noted that these symptoms were more pronounced during periods of overtraining than the moderately intense or taper conditions. [15] They also noticed a strong positive correlation between these symptoms of overtraining and salivary cortisol levels in the athletes. [15] Furthermore, swimmers who experienced a greater decline in performance during the overtraining period had greater increases in salivary cortisol compared to those with a less severe decline in performance. [15] This study provides further compelling evidence that it is crucial to monitor cortisol to prevent and treat symptoms of overtraining such as poor mental health and decline in performance.

You can use many methods to get elevated cortisol levels back into your optimal zone. In my three-part series on cortisol, I documented research on how whey protein’s primary component, alpha-lactabumin, decreases cortisol and increases production of the calming neurotransmitter serotonin. You can read the first part here and the third part here. In the second part, I examined four other methods to lower cortisol: sufficient sleep, expressing your thoughts in a journal, yoga, and self-compassion. You can check out the research behind those methods here. Additionally, our InsideTracker Recommendation Engine provides a handful of cool recommendations based on your demographics and personal preferences.

Key Takeaway: High-volume training can lead to elevated levels of cortisol, resulting in fatigue and decline in performance. If cortisol levels remain elevated for a prolonged period, athletes can face long-term negative health implications.

Recommendation: There are many ways to lower high levels of cortisol. Check out our previous blog posts and interventions in your InsideTracker Recommendation Engine to learn what is right for you!

Muscle aches that won’t go away? Monitor your creatine kinase (CK)

Creatine kinase (CK) is an enzyme found in our muscles, heart, and brain. When these tissues are uninjured and healthy, CK levels remain low. However, when there is injury, CK will become more active and spill over into the blood, thus increasing its serum levels.

Most scientists accept CK as an indicator of muscle damage. However, there are some important things to keep in mind when getting your CK tested along with your other biomarkers. First, CK generally increases after a single, intense workout. Sports physiologist Paola Brancaccio says, “High CK serum levels in athletes following absolute rest and without any further predisposing factors should prompt a full diagnostic workup with special regards to signs of muscle weakness or other simple signs that, in both athletes and sedentary subjects, are not always promptly evident.” [16]


Because of Brancaccio’s assessment, we recommend that athletes get tested after a 2-3 day period of low-to-moderate exercise. This means no heavy weightlifting, hundreds of kettlebell swings, or long runs. Additionally, Brancaccio notes that CK levels vary widely according to BMI, athletic status, gender, ethnicity, and genetics. Besides genetics, we ensure that your CK levels are put in context of your key demographics.

What can you do to make sure your CK remains low? Unfortunately, research on lifestyle interventions for treating CK is lacking. As a result, we suggest you make sure to get sufficient rest and recovery and participate in low-impact activities such as yoga. A relaxing massage or visit to the spa might also be a good alternative.

Key Takeaway: Get your CK tested after a couple of days of rest. High CK levels may indicate muscle damage and/or OTS.

Recommendation: Proper rest and recovery is the only real way to lower high CK levels.


Blood Analysis: A Winning Tool for Dealing with Overtraining

Dealing with many symptoms of overtraining—such as fatigue, depression, and muscle damage—can be prevented and managed by looking on the inside. Measuring indicators, such as testosterone and CRP, allows you to methodically break down problems associated with overtraining and make the necessary interventions to get back to optimal health and performance. At the end of the day, we want to provide you with the data and the science so you don’t suffer from a bad season, general fatigue and anxiety, or long-term complications such as depression and cardiovascular disease. 

How Is Your Training Affecting You?

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[1] Kreher, Jeffrey B., and Jennifer B. Schwartz. "Overtraining Syndrome: A Practical Guide." Sports Health: A Multidisciplinary Approach 4.2 (2012): 128-138.

[2] Koutedakis, Yiannis, and NC Craig Sharp. "Seasonal variations of injury and overtraining in elite athletes." Clinical Journal of Sport Medicine 8.1 (1998): 18-21.

[3] Maso, F., et al. "Salivary testosterone and cortisol in rugby players: correlation with psychological overtraining items." British Journal of Sports Medicine 38.3 (2004): 260-263.

[4] Tanskanen, Minna M., et al. "Serum Sex Hormone–Binding Globulin and Cortisol Concentrations are Associated with Overreaching during Strenuous Military Training." The Journal of Strength & Conditioning Research 25.3 (2011): 787-797.

[5] Cangemi, Roberto, et al. "Long‐term effects of calorie restriction on serum sex‐hormone concentrations in men." Aging cell 9.2 (2010): 236-242.

[6] Ridker, Paul M. "C-reactive protein—a simple test to help predict risk of heart attack and stroke." Circulation 108.12 (2003): e81-e85.

[7] Azar, Rima, Robert P. Nolan, and Donna E. Stewart. "Listening to the heart-brain talk: persistent depressive symptoms are associated with hsCRP in apparently healthy individuals at high risk for coronary artery disease." European Journal of Preventive Cardiology 19.4 (2012): 857-863.

[8] Fatouros, Ioannis G., et al. "Cell-free plasma DNA as a novel marker of aseptic inflammation severity related to exercise overtraining." Clinical Chemistry 52.9 (2006): 1820-1824.

[9] Kasapis, Christos, and Paul D. Thompson. "The effects of physical activity on serum C-reactive protein and inflammatory markers: a systematic review." Journal of the American College of Cardiology 45.10 (2005): 1563-1569.

[10] Stote, K. S., et al. "Effect of cocoa and green tea on biomarkers of glucose regulation, oxidative stress, inflammation and hemostasis in obese adults at risk for insulin resistance." European journal of clinical nutrition 66.10 (2012): 1153-1159.

[11] Valtueña, Silvia, et al. "Food selection based on total antioxidant capacity can modify antioxidant intake, systemic inflammation, and liver function without altering markers of oxidative stress." The American journal of clinical nutrition87.5 (2008): 1290-1297.

[12] Lupien, S. J., de Leon, M., De Santi, S., Convit, A., Tarshish, C., Nair, N. P. V., & Meaney, M. J. (1998). Cortisol levels during human aging predict hippocampal atrophy and memory deficits. Nature Neuroscience 1(1), 69-73.

[13] Chandola, Tarani, Eric Brunner, and Michael Marmot. "Chronic stress at work and the metabolic syndrome: prospective study." BMJ332.7540 (2006): 521-525.

[14] Palacios, Gonzalo, et al. "Biomarkers of physical activity and exercise." Nutr Hosp 31.Supl 3 (2015): 237-244.

[15] O'Connor, Patrick J., et al. "Mood state and salivary cortisol levels following overtraining in female swimmers." Psychoneuroendocrinology 14.4 (1989): 303-310.

[16] Brancaccio, Paola, Nicola Maffulli, and Francesco Mario Limongelli. "Creatine kinase monitoring in sport medicine." British Medical Bulletin 81.1 (2007): 209-230.

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