Rest and readiness: What is the optimal nap length during night shifts to improve productivity, performance and safety?

Arm 1: 15 minute nap condition Intervention: Participants are assigned to a 15 min nap opportunity during a scheduled break, within a 12-hour simulated night shift protocol. Who delivers it and their relevant expertise: The research is delivered by a research team with extensive expertise in sleep and fatigue research. There will be one postdoctoral research fellow, two PhD candidates and trained research assistants conducting the data collection. How is it delivered: The study is conducted in a controlled sleep laboratory. Participants are assigned to individual bedrooms within a six-bedroom sleep laboratory facility. How often and for how long: Each experimental condition lasts 40 hours and includes one adaptation night and the following night is a 12-hour simulated night shift where cognitive test batteries and simulated work tasks will be completed throughout the shift. Participants reside in the laboratory for the duration of each condition. The study uses a randomised counterbalanced design with a 5–7-day washout period between conditions. Where is it delivered: A state of the art six-bedroom sleep laboratory facility. Adherence: Participants are continuously monitored during laboratory stays. Between experimental conditions, adherence is supported through sleep diaries, food diaries and actigraphy monitoring. Arm 2: 30-minute nap condition Intervention: Intervention: Participants are assigned to a 30 min nap opportunity during a scheduled break, within a 12-hour simulated night shift protocol. (All other components are identical to Arm 1) Arm 3: 60-minute nap condition Intervention: Intervention: Participants are assigned to a 60 min nap opportunity during a scheduled break, within a 12-hour simulated night shift protocol. (All other components are identical to Arm 1)