Exercising could help to induce changes in skeletal muscle, purging the blood of an unwanted substance that accumulates during stress, according to a new study published in the journal Cell.

Physical exercise has increasingly been linked to more specific health benefits, including the potential protection from stress-induced depression.

This latest study from researchers at the Karolinska Institutet in Sweden has now shed light on the actual mechanisms that mediate this protective effect.

A protein called PGC-1a1 is known to increase in skeletal muscle following exercise, with the substance aiding muscle conditioning. As part of the study, experts used genetically modified mice with high levels of PGC-1a1 in skeletal muscle to replicate the impact of well-trained muscles.

The mice were placed alongside normal control mice and then exposed to a manufactured stressful environment, which saw the use of loud noises, flashing lights and reversed circadian rhythm at irregular intervals.

The specimens were subject to the mild stress for five weeks, with the control mice developing depressive behaviour, however those with well-trained muscle characteristics had no depressive symptoms whatsoever.

It was also discovered that the modified mice had higher levels of an enzyme known as KAT, which aids the production of kynurenine acid, a protective mechanism that works against the stress symptom of kynurenine. It is known that patients with mental illness tend to show high levels of kynurenine.

"It's possible that this work opens up a new pharmacological principle in the treatment of depression, where attempts could be made to influence skeletal muscle function instead of targeting the brain directly," said Jorge Ruas, principal investigator, according to Science Daily.

"Skeletal muscle appears to have a detoxification effect that, when activated, can protect the brain from insults and related mental illness."

Away from impacts on depression, other research has alluded to the benefits of exercise on cognition and brain function, with one study suggesting that losing weight could help to increase brain power.

Another study has also stated that aerobic fitness helps to garner more efficient functioning in the brain.