Researchers at Manchester Metropolitan University in the UK found that strenuous exercise is better at boosting a positive mood than moderate activity.
Lead researcher Nickolas Smith said the results of their study could have implications for the type of exercise recommended to produce the so-called "feel good factor".
"There are also implications regarding how people new to regular exercise should expect to feel during the exercise itself if they are to experience post-exercise mood benefits," Smith was quoted as saying by the Daily Telegraph.
For their study, the researchers looked at 11 people, who were asked to take part in two 20-minute long work-outs, one moderately intensive and one highly intensive.
The mood of the participants was measured before, during, immediately after and 20 minutes after each work out.
They found volunteers exhibited no mood improvements after moderate exercise.
However, 20 minutes after the end of the strenuous work-out -- which got them breathing heavily and their muscles burning -- the participants reported feeling more positive.
Psychiatrists believe that mood improves after vigorous exercise -- a phenomenon known as the "runner`s high" -- because it triggers the release of endorphins, a type of neurotransmitter in the brain that help combat pain.
The findings were presented at the British Psychological Society Annual Conference in Glasgow.