Human muscles 'talk' to other parts of the body during exercise by dispatching protein messages that can help fight disease, a new Australian-led study shows.

Researchers have shed new light on how muscles "talk" to other parts of the body during exercise, explaining why being active is good for you, from head to toe, and especially for your liver.

Australian scientists have exposed new secrets about a kind of "postal system" that muscles use to communicate with other parts of the body, including vital organs.

Their findings offer hope to people with an increasingly common form of liver disease that can lead to cancer, and for which there is currently no treatment.

Professor Mark Febbraio, from Sydney's Garvan Institute of Medical Research, says human muscles have been found to dispatch messages to other parts of the body by releasing protein-packed "packages" called vesicles.

These packages appear to carry important messages that tell organs to respond differently during exercise.

In the case of the liver, many more of these packages arrive during exercise, delivering a family of enzymes that allow the organ to break down and metabolise sugar rather than store it as fat.

The findings have Prof Febbraio excited for sufferers of fatty liver disease who can go on to develop cancer.

"Nonalcoholic steatohepatitis, or NASH, is a tsunami of disease at the moment, and it's very insidious because we know NASH can lead to cirrhosis, which can lead to cancer," Prof Febbraio says.

"Liver cancer is going up and one of the major contributers to the increase is obesity and fatty liver. What our paper suggests is that if you have fatty liver disease, exercise is a treatment for that disease."

The findings could one day have implications for other forms of disease too.

"They don't just go to the liver, and we know from the evidence that exercise has a beneficial effect when it comes to other diseases, such as degenerative brain disease, depressive illnesses, and certain forms of cancer," Prof Febbraio says.

He and study co-leader Dr Martin Whitham and colleagues from the University of Sydney and the University of Copenhagen are already planning more research on the body's postal delivery system and how it might be harnessed to fight disease.

They intend to carry out a study to tag, transfer and track protein packages in animals, to determine if beneficial ones can be transplanted.

"For example, in Alzheimer's disease, we know there are certain proteins that are dysfunctional," he said.

"If you had a mechanism of replacing those, by transfer, that's not outside the realms - that this is potentially a therapeutic strategy to treat some of these diseases."

The research has been published in the latest edition of the journal Cell Metabolism.