Experience From - Bruce Ketchum , Karl King , Rich Schick ,

Bruce Ketchum

Karl King wrote:

"If you want to be thin and unhealthy, run lots and lots and lots of slow miles so that your body fills up with cortisol, eating away fat and muscle."

Then Paul wrote:

"Karl, You scared me to death. What in the world is cortisol?? Is "slow" defined in some way that I can measure and avoid? Isn't ultra running by definition "slow"??"
Cortisol, also known as hydrocortisone, is a hormone from the adrenal cortex; it is the principal glucocorticoid. A synthetic preparation is used for its anti-inflamatory actions.

Glucocorticoids are essential to life. They enable us to adapt to external changes and stress. They also maintain fairly consistent plasma glucose levels even when we go for long periods without ingesting food. Cortisol is the major corticosteroid. It is responsible for about 95% of all glucocorticoid activity in the body. Cortisol is known to:

As you can see, cortisol is not necessarily a bad thing. In fact, without it we would not at all get along very well. Some elite level endurance athletes have even experimented with cortisol-like drugs to enhance performance. Understandably, blocking that debilitating achiness that comes on late in long endurance events would certainly provide an advantage. There really is nothing wrong with having elevated cortisol during exercise; however, if it stays elevated after exercise, then it may be a problem.

Lots of worries in life, a stressful job, and risk taking can all elevate cortisol and keep it up. This may prevent the endurance athlete from recovering adequately. Cortisol is a so-called catabolic (breakdown) hormone, the opposite of an anabolic hormone. Having cortisol elevated at other times other than exercise may prevent the athlete from recovering at an optimal rate.

One of the best ways to control elevated cortisol levels is to keep well hydrated. There is some recent science showing that dehydration causes cortisol levels to increase.

Consume plenty of carbohydrates and good quality protein to potentially deflect the ill effects of elevated cortisol.

There are also some fancy supplements available in health food stores that have been suggestion to reduce cortisol production. They are acetyl-L-carnitine and phosphatidylserine. They are expensive supplements, but if cost isn't a concern then they may be something to experiment with. Watch for more on these two supplements in EndurePlus.


Miller-Keane, Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health (6th Edition). W.B. Saunders Co., 1997.

Wilmore-Costill, Physiology of Sport and Exercise. Human Kinetics, 1994.

Karl King

Cortisol is a horomone that the body produces when under stress, such as after hours of running. Don't worry about it (worry causes stress too). Cortisol is great stuff to have *during* an ultra, but very bad *after* a long run because it delays the healing and growth your body needs. It can take a couple days for the cortisol level in the blood to get back to normal.

The problem is not slow running, but running too often, and too long relative to the rest taken between training sessions. Effective training is a series of: stress, rest, stress, rest.... Overtraining is a series of: stress, stress, stress...

If you do not rest adequately between sessions, the level of cortisol can stay high for a long time, giving a sunken, tired and depleted look.

Note that you can't and shouldn't try to avoid long runs for ultras. One could run 70 mile weeks by doing a 10 mile run every day. That won't get you through an ultra, though you'd be good at the 10K to half marathon distance. The main reason for doing long runs is not to rack up miles, but to train your body to produce cortisol and other stress hormones after hours of running. Those hormones allow the body to withstand the stresses of long runs. Since it takes about 15 miles of running before your body starts reacting to the stress, the effective part of a long run is the part after 15 miles. Thus, a 25 mile long run is much more effective than a 20 mile long run:

( 25 - 15 )= 2*( 20 - 15 )

So, don't shy away from long runs, just get adequate rest afterward so your body dumps the cortisol and grows stronger from the stress. Runners with a long history of running may have no problem doing a long run every weekend. Runners who are newer to ultra running may benefit from running long one weekend, then short to medium the next weekend - or running long 2 weekends in a row, then running short the third.

Some symptoms of overtraining are: sunken look around the eyes, poor sleep patterns, and lack of motivation. If you have those, you probably have too much cortisol buildup and need to rest for a few weeks until your motivation to train rebounds.

Rich Schick

What follows are several abstracts I bumped into reviewing the cortisol issue, read or delete as you see fit.

Source: J Sports Med Phys Fitness, 37(1):7-17 1997 Mar

Overtraining can be defined as "training-competition recovery imbalance", that is assumed to result in glycogen deficit, catabolic anabolic imbalance, neuroendocrine imbalance, amino acid imbalance, and autonomic imbalance. Additional non-training stress factors and monotony of training exacerbate the risk of a resulting overtraining syndrome. Short-term overtraining called overreaching which can be seen as a normal part of athletic training, must be distinguished from long-term overtraining that can lead to a state described as burnout, staleness or overtraining syndrome. Persistent performance incompetence, persistent high fatigue ratings, altered mood state, increased rate of infections, and suppressed reproductive function have been described as key findings in overtraining syndrome. An increased risk of overtraining syndrome may be expected around 3 weeks of intensified/prolonged endurance training at a high training load level. Heavy training loads may apparently be tolerated for extensive periods of time if athletes take a rest day every week and use alternating hard and easy days of training. Persistent performance incompetence and high fatigue ratings may depend on impaired or inhibited transmission of ergotropic (catabolic) signals to target organs, such as:

  1. decreased neuromuscular excitability
  2. inhibition of alpha-motoneuron activity (hypothetic)
  3. decreased adrenal sensitivity to ACTH (cortisol release) and increased pituitary sensitivity to GHRH (GH release) resulting in a counter-regulatory shift to a more anabolic endocrine responsibility
  4. decreased beta-adrenoreceptor density (sensitivity to catecholamines)
  5. decreased intrinsic sympathetic activity
  6. intracellular protective mechanisms such as increased synthesis of heat-shock proteins (HSP 70) represent a complex strategy against an overload-dependent cellular damage.

Source: J Appl Physiol, 81(6):2627-36 1996 Dec

The purpose of this investigation was to study the effects of endurance exercise on male reproductive function (sex hormones and seminograms). Professional cyclists [n = 12; mean age 24 +/- 2 (SD) yr], elite triathletes (n = 9; 26 +/- 3 yr), recreational marathon runners (n = 10; 32 +/- 6 yr), and sedentary subjects (control group; n = 9; 30 +/- 4 yr) were selected as subjects. for each group, the following parameters were measured three times during the sports season (training period: winter; competition period: spring; resting period: fall): percentage of body fat, hormonal profile (resting levels of follicle-stimulating hormone, luteinizing hormone, total and free testosterone, and cortisol), and seminograms (quantitative parameters sperm volume and sperm count; qualitative parameters: sperm motality an morphology). The following comparisons were made in the measured parameters: 1) within groups (longitudinal design) and 2) between groups in each of the three periods (cross-sectional design) and over time (mixed design). In addition, both the volume and the intensity of training of each subject during the season (except for the control group) were quantified...........................A lower sperm motility (46.2 +/- 19.5%), however, was observed in the cyclists during the competition period when compared either with the other groups during this same period (P < 0.05) or with themselves during the other two periods of study (P < 0.01). In any case, the later phenomenon was attributed to physical factors associated with cycling, such as mechanical trauma to the testis and/or increased gonadal temperature. In conclusion, our findings suggest that endurance exercise does not adversely affect the hypothalamic-pituitary-testis axis.

Source: Int J Sports Med, 17(8):554-8 1996 Nov

Although there are various descriptive reports concerning exercise-induced gastrointestinal distress, the role of gastrointestinal hormones and/or enzymes is not definitively established. In this study we investigated the behaviour of pepsinogens (PGI and PGII) after an endurance race performed at an altitude of 4,300 m by 13 well-trained marathon runners, with the aim to establish their interrelationship with gastrointestinal distress and with the modifications of gastrin and cortisol. The data of the present study indicate that the potential damage of gastrointestinal apparatus in mountain marathon runners is not related to the above mentioned hormones.

Source: Psychopharmacology (Berl), 118(3):260-6 1995 Apr

Although it is generally accepted in the sporting world that adrenocorticotropic hormones (ACTH) and corticosteroids enhance maximal performance, this claim has never been scientifically corroborated. In a counterbalanced, double-blind design, 1 mg ACTH or placebo was injected into 16 professional cclists. They cycled for 1 h on a bicycle ergometer at a submaximal level, defined as 60% of maximal performance on a pretest with a load increase of 50 W per minute. After 1 h, load was increased by 10 W per minute until exhaustion. No increase of maximal performance was observed with ACTH, eiter on the day of drug intake, or on the following day, although substantial increases were measured in physiological variables such as cortisol, glucose, and white corpuscle concentrations. Feelings of fatigue, which were continuouslyself-rated, were diminished only during submaximal performance. The present technique of systematically distinguishing between physiological psychological, and performance measurements could help in explaining the persistent belief in the performance enhancing properties of ACTH and other doping substances.