Psychologists have long known that written instructions are more likely to be followed than spoken advice. Slovenian doctors will attempt to exploit this brain hack by issuing special exercise referrals to patients.

This is the idea behind Exercise on Prescription, a new initiative spearheaded by the Association of Cancer Patients that aims to get all patients, not just those with cancer, to exercise more to improve their health outcomes.

"Physical activity is one of the most effective natural remedies. Regular exercise reduces the risk of heart disease, diabetes and other chronic conditions," says doctor Dr. Vedran Hadžić, who teaches sport medicine at the Faculty of Sport, University of Ljubljana.

Such initiatives have been around since the 1990s and several countries have been trying them out, including New Zealand and the UK. These experiments show that people respond better to written advice, according to Dr. Matej Kokalj Kokot, an occupational medicine specialist.

The initiators have looked at the experiences of these countries before they devised the Slovenian system. One thing they have decided on is to closely mimic the way drugs are prescribed.

Doctors will be given a green booklet with referrals that look almost exactly like the green referrals for prescription drugs. The referral lists the most common types of exercises and the doctor can prescribe exercise intensity and duration.

The back side of the referral form provides answers to the most common questions that patients may have.

The medical profession still does not perceive exercise as a serious enough form of treatment, Hadžić says. "It is often easier to write a prescription for a pharmacological treatment that talking to the patient to see how physically active they are and what we can do about that," he said.