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

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_p ² = .03), fatigue (p = .001, η_p ² = .05), stress (p = .005, η_p ² = .04) and lack of activation (p = .011, η_p ² = .04), alongside enhanced mental performance capacity (p = .008, η_p ² = .04) and overall recovery (p = .014, η_p ² = .03) compared to control. Reaction time in the Simon task (Group × Time: p < .001, η_p ² = .07) was enhanced in the NSDR group immediately post-intervention (p = .012), while no differences were observed at later assessments. Physiological responses showed a significant Group × Time interaction for heart rate, indicating a greater relative reduction during NSDR compared to control, alongside a smaller rise in skin temperature in the NSDR condition (p < .05). No significant effects were observed for physical performance outcomes (p > .05). These findings suggest that NSDR was associated with consistent improvements in perceptual outcomes, while cognitive findings were transient and physiological findings were modest and should be interpreted cautiously. These results support further evaluation of NSDR as a brief, time-efficient acute rest intervention.