Researchers suggest that the feeling that one gets after a good run, also known as 'runner's high', is similar to the feeling that one gets after having marijuana, the standard daily reports.

Earlier, researchers suggested that the endorphins released after running are responsible for the relaxed and feel good sensation that the runner gets after a strenuous stretch of running.

Endorphins are natural painkillers and earlier studies have revealed that intense physical activity leads to massive spikes in this compound. This led researchers to believe that it was the release of endorphins that was responsible for runners experiencing the feeling known as 'runner's high'.

However, later studies suggested that the size of the endorphin molecules is too large to fit in the blood barrier of the brain and to attach themselves to the receptors of the brain.

Researchers from the Central Institute of Mental Health of the University of Heidelberg have found other compounds, called endocannabinoids, that may lead to the feeling called 'runner's high'. After an intense and long run, our body produces beta-endorphin called opioid as well as anandamide called endocannabinoid.

Endocannabinoids aren't naturally produced in the body. Studies have shown its numbers spike after intensive exercise. This molecule is also found in marijuana or cannabis.

In an experiment conducted on rodents, researchers found that rodents experienced something like a runner's high.  When the researchers blocked the endorphin effect, the behavior of the mice remained unaffected. However, when they blocked endocannabinoids, the rodents weren't relaxed or calm anymore.

This led the researchers to conclude that it wasn't endorphins that caused the high but endocannabinoids.