An adaptogen is a substance or metabolic regulator that improves the 
body's ability to adapt to various nonspecific environmental stressors, such as heat, cold, exertion, time changes, trauma, sleep deprivation, toxic exposure, radiation, infection, fatigue, and emotional stress. Most adaptogens are herbs.
A substance or herb has to meet the following criteria to be labeled as an adaptogen:
- They should not cause disturbances in normal physiological functions of the body.
- They should improve the body`s resistance against environmental stressors.
- They should help normalize disordered physiological functions of the body.
Adaptogens help the body cope easily with a wide variety of stresses, increase efficiency of natural healing system, and improve the body`s natural resiliency and adaptability. They could be used by both healthy and sick people. However, they cannot cure or treat any diseases.
Athletes benefit from adaptogens as they face many stressors such as intense training, time changes, fatigue, and pre-competition anxiety. They help athletes speed up recovery, improve their general well-being, and support their bodies against stress.
It has been suggested that adaptogens to be taken in “cycle”. That means you may take an adaptogen for a short period of time and then stop taking it for a while. This is called “periodization of adaptogen”, which is usually 3 weeks continuous consumption followed by one week rest before resuming.
When adaptogens normalized the disordered physiological functions of an organ, consuming them for a longer period would least likely show additional benefits.
Many herbs and even spices have been classified as adaptogens. The most commonly used adaptogens by athletes have been listed below.
Click on them below for detailed infromation about athletic and non - athletic benefits 
of adaptogens: