How Cortisol Effects Performance

Cortisol, known as the regulator of immune response, is a hormone controlled by the adrenal cortex. This powerful hormone is also known as an adrenalcorticol hormone, a glucocorticoid and hydrocortisone or simply cortisone. Cortisol has a catabolic (muscle breakdown) effect on tissue and is associated with a decrease in anabolic (muscle growth) hormones like IGF-1 and GH. Thus reducing levels of cortisol is ideal for an athlete to achieve tissue growth and positive adaptations to exercise training. Playing many different roles in the body, cortisol can have a negative impact on sleep, mood, sex drive, bone health, ligament health, cardiovascular health and athletic performance, potentially causing fatigue and inflammation. Its primary functions are to increase protein breakdown, inhibit glucose uptake and increase lipolysis (the breakdown of fats).

While cortisol in normal amounts is necessary for proper metabolic function, a chronic elevated cortisol level has adverse effects on health, mood, body composition and performance. Elevated cortisol secretion from physical or mental stress causes fat, protein and carbohydrates to be rapidly mobilized in order for the body to take action against the stressor. This is sometimes referred to as the ‘fight or flight’ response. The mobilization of these nutrients in addition to epinephrine and a number of other endocrine hormones allows the body to take quick action when presented with stress. During this mobilization, cortisol and adrenaline increase while DHEA (Dehydroepiandrosterone) and testosterone decrease. A chronic elevated cortisol level causes the body to enter a state of constant muscle breakdown and suppressed immune function, increasing risk of injury while reducing muscle.

It is only with chronic elevated cortisol levels that performance will suffer, but the effect is dramatic. Excess cortisol suppresses the immune system, producing a greater risk of upper respiratory infections and depressed levels of testosterone. On top of that, the body will be in a catabolic state — breaking down muscle and storing fat. In addition to reducing muscle and getting sick, suppressed testosterone means suppressed recovery. Aerobic and anaerobic muscle fibers need time to repair and recover from hard workouts to improve their capacity to exercise. Elevated cortisol and suppressed testosterone do not allow maximized recovery, leading to slower performance gains. A Swiss study of elite male cyclists suggested that ratios of anabolic to catabolic hormones (ie. testosterone/cortisol or IGF-1/cortisol) may be useful markers for the detection of overtraining (Hug et al. 2003). In fact, scientists use this Free Testosterone/Cortisol ratio to evaluate an athlete’s training state. A ratio where cortisol is elevated indicates overtraining, so the modulation of this ratio can be key for those athletes who are susceptible to overtraining.

A literature review of hormonal responses to exercise by Steinacker et al. (2003) suggested that with glycogen deficiency, cortisol levels are elevated and induce a “myopathy-like state” in skeletal muscle.

And it’s not only what is eaten but when. Breakfast is a necessity, which will help regulate blood sugar and cortisol prior to workouts. In a recent paper by Dr. Mark Davis and Dr. Adrienne Brown, it was clearly demonstrated that ingesting carbohydrates during exercise modulates many of the endocrine hormones, including cortisol. To ensure that glycogen stores are not depleted, carbohydrates should be ingested while exercising along with a high quality recovery drink with high levels of carbohydrates immediately following exhaustive exercise. The bottom line: endurance training should not be attempted on a high protein, low carbohydrate diet.

A high dose of B vitamins and calcium can help regulate the endocrine hormones necessary for proper cortisol control. Supplementing with 4+ grams of branched chain amino acids (BCAAs) and 6+ grams glutamine following exhaustive exercise can have a dramatic effect on cortisol. In fact, in a 25-week study of intercollegiate swimmers the group supplementing with BCAAs and glutamine showed a significant decrease in serum cortisol. A study done by Stone entitled “Effects of Vitamin C on cortisol and the Testosterone: cortisol ratio” showed a decrease in cortisol levels in 17 junior elite weight lifters. This study also showed that the individuals taking vitamin C (an extra gram a day) improved their testosterone to cortisol ratio by over 20%. This type of decrease in cortisol can lead to increased muscle and connective tissue hypertrophy and enhanced recovery from training. Since vitamin C also decreases the chance of suffering from a cold or flu infection by 30% and may aid in collagen synthesis, it would be wise to take some extra vitamin C when involved in an intense training program. Beta-Carotene, which is often times used for healthy skin function, may also minimize cortisol levels according to Dr. Sapse. He suggested this in an abstract he presented at the 1997 conference on cortisol and anti-cortisols.

Cortisol References

Bishop NC, Gleeson M, Nicholas CW, Ali A. Influence of carbohydrate supplementation on plasma cytokine and neutrophil degranulation responses to high intensity intermittent exercise. Int J Sport Nutr Exerc Metab 2002 Jun;12(2):145-56

Brenner IK, Zamecnik J, Shek PN, Shephard RJ. The impact of heat exposure and repeated exercise on circulating stress hormones. Eur J Appl Physiol Occup Physiol 1997;76(5):445-54

Cook NJ, Ng A, Read GF, Harris B, Riad-Fahmy D. Salivary cortisol for monitoring adrenal activity during marathon runs. Horm Res 1987; 25(1):18-23

Ding JH, Sheckter CB, Drinkwater BL, Soules MR, Bremner WJ. High serum cortisol levels in exercise associated amenorrhea. Ann Intern Med 1988 Apr;108(4):530-4

Gleeson M, Lancaster GI, Bishop NC. Nutritional strategies to minimise exercise-induced immunosuppression in athletes. Can J Appl Physiol 2001;26 Suppl:S23-35

Green, KJ, Croaker, SJ, Rowbottom, DG. Carbohydrate supplementation and exercise-induced changes in t-lymphocyte function. Journal of Applied Physiology 2003 95: 1216-1223.

Hug M, Mullis PE, Vogt M, Ventura N, Hoppeler H. Training modalities: over-reaching and over-training in athletes, including a study of the role of hormones. Best Pract Res Clin Endocrinol Metab. 2003 Jun; 17(2): 191-209.

J Mark Davis, Adrienne S. Brown Carbohydrates, Hormones and Endurance Performance. Gatorade Sports Science Institute® 2001; 14 (1).

Lac G, Berthon P. Changes in cortisol and testosterone levels and T/C ratio during an endurance competition and recovery. J Sports Med Phys Fitness 2000 Jun;40(2):139-44

O’Connor PJ, Corrigan DL. Influence of short-term cycling on salivary cortisol levels. Med Sci Sports Exerc 1987 Jun;19(3):224-8

Ronsen O, Kjeldsen-Kragh J, Haug E, Bahr R, Pedersen BK. Recovery time affects immunoendocrine responses to a second bout of endurance exercise. Am J Physiol Cell Physiol 2002 Dec;283(6):C1612-20

Steinacker JM, Lormes W, Reissnecker S, Liu Y. New aspects of the hormone and cytokine response to training. Eur J Appl Physiol. 2003 Nov 8 [Epub ahead of print].

Textbook of Medical Physiology; ninth edition. Guyton and Hall, W.B. Saunders Company, Philadelphia,

PA Copyright 1996 Textbook Overtraining in Sport: Kreider R.B. ;A.C. Fry, and M.L. O’Toole, Human Kinetics; pgs 323 and 329. Copyright 1998.

The Cortisol Connection. Shawn M. Talbott PH.D. Publishers Group West, Hunter House Inc, Alameda CA Copyright 2002

1 reply
  1. Calebe
    Calebe says:

    excellent article!
    Thank you for all that explanation. I’m new at road cycling and now I will pay more attention a take some carbs with me every training.

    Reply

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