Time course of perceptual, cognitive, physical and physiological responses to a single non-sleep deep rest session in physically active young adults.

Non-sleep deep rest (NSDR), a brief guided relaxation technique involving slow breathing and sequential body awareness, has recently been proposed as a practical rest strategy. However, evidence on its short-term time course and physiological responses remains limited. This study examined the effects of a brief NSDR session on perceptual, cognitive, physical, and physiological outcomes in physically active young adults. In a parallel-group design, 102 participants (mean age: 22 ± 3 years) were randomly allocated to either a 10-min guided NSDR protocol (n = 51) or a control condition (n = 51). Perceptual outcomes included sleepiness, fatigue, readiness to perform, as well as muscular stress, lack of activation, negative emotional state, overall stress, physical performance capacity, mental performance capacity, emotional balance and overall recovery (short recovery and stress scale), alongside cognitive (Simon task) and physical (handgrip strength and countermovement jump) performance assessed at baseline, immediately, 20 min and 40 min post-intervention. Physiological responses (heart rate, heart rate variability and skin temperature) were recorded continuously during the intervention. Linear mixed-effects models showed that NSDR resulted in significant Group × Time improvements across perceptual measures, including reduced sleepiness (p = .009, η