A method and apparatus for determining an individualized need for sleep and real-time indication of sleep pressure from physiological data, including at least heart rate data. The method may first involve collecting certain demographic information about the user, such as age data. A sleep need value may then be calculated for the user, based on their expected need for sleep, based on factors such as high chronic stress, acute and chronic training load (for the individual and as an absolute matter), and any other factors such as altitude or alcohol consumption. A sleep pressure value may then be calculated throughout the day, based on the user's activity level and their sleep need (including, for example, sleep debt information), which may then be used to provide feedback to the user as to when they should go to bed.
A METHOD AND APPARATUS FOR DETERMINING SLEEP NEED AND SLEEP PRESSURE BASED ON PHYSIOLOGICAL DATA