The green prescription study: a randomized controlled trial of written exercise advice provided by general practitioners.

Abstract
The purpose of this study was to determine whether written advice from general practitioners increases physical activity among sedentary people more than verbal advice alone. Sedentary patients (n = 456) received verbal advice on increasing physical activity and were then randomized to an exercise prescription (green prescription) group or a verbal advice group. The number of people engaging in any recreational physical activity at 6 weeks increased substantially, but significantly more so in the green prescription group. Also, more participants in the green prescription group increased their activity over the period. A written goal-oriented exercise prescription, in addition to verbal advice, is a useful tool for general practitioners in motivating their parents to increase physical activity.