[Morgan Pillsbury is a recent graduate of Elon University and an Athletic Development Intern at Athletic Lab]
Serum hormone levels, such as testosterone and cortisol, have been used as markers for training intensity and recovery for many years now. Cortisol is a stress hormone, therefore increasing during exercise by acting upon the catecholamines. An increased cortisol level has an adverse effect on testosterone levels, and a low testosterone to cortisol (T:C) ratio has been shown to have adverse effects on performance (Fry et al., 1994). This makes the T:C ratio very important for monitoring the athlete’s response to exercise intensity in order to prevent overtraining. This can then be applied to find an optimal time to train throughout the day based on hormone levels.
Well conditioned athletes have more controlled cortisol secretion during exercise, however, when an athlete is overtrained, the cortisol rises more and testosterone decreases, creating a low T:C ratio. This is observed more in strength training athletes compared to endurance athletes. Hoogeveen & Zonderland (1996), concluded that a decreased T:C ratio does not necessarily represent overtraining in professional cyclists. When cortisol inhibits testosterone during strength training, it results in a catabolic effect, breaking down the muscle and tendon tissue.
How can this information be used to optimize performance? Since testosterone and cortisol fluctuate throughout the day, there are certain times that the ratio is most optimal for training. Dimitriou (2002), found that stress responses were highest and immune response was lowest in the morning, with opposite being true in the evening. This suggests a schedule of higher-intensity workouts in the afternoon and leaving the morning for aerobic exercise. Upon first waking up, cortisol and testosterone are both at their peaks, providing an effective balance for prolonged endurance activity. As the evening rolls around, say 5pm, testosterone reaches another peak and cortisol has decreased, providing an increased T:C ratio and an optimal strength training opportunity. With this being said, obviously there are many personal variables, such as family or work, that do not allow for this schedule, which doesn’t mean that morning training is ineffective.
According to the research and the increasingly accessible serum/blood monitoring tools, the testosterone to cortisol ratio is effective in observing the level of training as well as potential overtraining in recovery. This information may allow athletes to alter their sleeping or dietary habits in order to best prepare themselves for training, or to alter their training schedule based on the previously discussed fluctuations of the ratio throughout the day.
- Dimitriou L, Sharp NCC & Doherty M. (2002). Circadian effects on the acute responses of salivary cortisol and IgA in well trained swimmers. Br J Sports Med, 36: 260-264.
- Fry, AC., Kraemer, WJ., Stone, MH., Warren, BJ., Fleck, SJ., Kearney, JT., & Gordon, SE. (1994). Endocrine responses to overreaching before and after 1 year of weightlifting. Canadian Journal of Applied Physiology, 19(4): 400–410.
- Hoogeveen AR & Zonderland ML. (1996). Relationships between testosterone, cortisol and performance in professional cyclists. Int J Sports Med, 17(6): 423-428.