Folks often feel more alert and savvy after a great workout, and dopamine might be the reason why.

A small, new study by British and Japanese researchers found higher levels of the "feel good" brain neurotransmitter were released by men during exercise.

In turn, that seemed tied to better performance on thinking tests, the researchers said.

“These latest findings support our previous theory that cognitive performance during exercise is affected by changes to brain-regulating hormones, including dopamine,” said study co-author Dr. Joe Costello.

He's at the University of Portsmouth's School of Sport, Health & Exercise Science, in England.

The findings were published recently in the The Journal of Physiology

In the study, Costello and colleagues team had 52 men engage in three separate experiments.

All were having their brain activity monitored with sophisticated PET imagery during the experiments.

In one trial, men were asked to work on mentally challenging tasks while cycling lying down.

The second experiment had the men complete the same tasks, but this time they got "electrical muscle stimulation," rather than a workout.

The third experiment had them completing mental tasks while working out and getting the electrical muscle stimulation.

Based on data from the PET scans, Costello's group found a surge in dopamine release in the brain while men were actively working out — what's known as "voluntary" exercise.

That uptick in dopamine was linked to improvements in carrying out the mental tasks.

No such effect was seen when muscles were simply stimulated electrically — what's known as "involuntary" exercise.

“We wanted to remove voluntary muscle movement for part of the study, to see if the process in which acute exercise improves cognitive performance is present during manufactured exercise," study lead author Soichi Ando explained in a University of Portsmouth news release.

"Our results indicate that the exercise has to be from the central signals of the brain, and not just the muscle itself," Ando said. He's an associate professor at the Health & Sports Science Laboratory at the University of Electro-Communications, in Japan.

“This suggests that when we tell our central command to move our body during a workout, that’s the process which helps the dopamine release in the brain," Ando added.

Costello stressed that dopamine release probably isn't the only factor that makes exercise so great for staying sharp.

“There could also be a number of other psychophysiological factors including cerebral blood flow, arousal and motivation that play a part," he said.

The bottom line, according to Costello: "These findings support growing evidence that exercise prescription is a viable therapy for a host of health conditions across the lifespan.”