A new piece of research will come as a relief to fitness lovers everywhere – as it confirms that exercise isn’t bad for your memory after all.

Fears over potential fitness-related memory loss had been caused by a study on mice, published in the influential journal Science in May 2014, which found that exercise led to mice forgetting what they’d already learned.

The worrying conclusion was based on exercise resulting in neurogenesis – the creation of new neurons – in the hippocampus, a key brain region for learning, memory and mood regulation.

The 2014 study suggested that the creation of these new neurons seemed to erase memories that the mice had formed before they started the exercise regimen.

To test this, the researchers removed the extra neurons created through exercise, and the mice suddenly were able to remember again.

“It stunned the field of hippocampal neurogenesis,” says Ashok K. Shetty, a professor at the Texas A&M College of Medicine (TAM).

“The mice who exercised had a large number of new neurons, but somehow that seemed to break down the old connections, making them forget what they knew.”

“It was a very well-done study, so it caused some concern that exercise might in some way be detrimental for memory.”

Shetty and his team at TAM decided to replicate this earlier research, using rats instead of mice. Rats are thought to be more like humans physiologically, with more similar neuronal workings.

Publishing its findings in the Journal of Neuroscience this month, the group led by Shetty concluded that exercise does indeed result in much greater neurogenesis – but among rats the phenomena didn’t cause any degradation in memories.

“We had completely contradictory findings from the 2014 study,” says Maheedhar Kodali, one of the study’s authors. “Now we need to study other species to fully understand this phenomenon.”

What is clear from both studies, however, is that exercise does speed up the development of neurons in the brain – and could explain why exercise is an effective antidepressant.

“This is pretty clear evidence that exercise greatly increases neurogenesis in the hippocampus, which has functional implications as it is important for maintaining normal mood function” Kodali said.

To read the full study in the Journal of Neuroscience, click here.