Due to work, family, social and community obligations, millions of Americans cut back on sleep for several nights in a row before having an opportunity to catch up. When the opportunity does arise, it may only be for a single night, before the cycle of insufficient sleep repeats. This study investigated what happens to human biology when insufficient sleep becomes chronic and opportunities for recovery sleep are intermittent. It also investigated recovery sleep itself, and the biological processes involved in reversing the effects of an accumulated sleep deficit due to insufficient sleep duration.