Revolutionary Study Uncovers Fatigue Recovery Through Sleep Metabolism

In a groundbreaking research initiative, Ritsumeikan University and Inoac Corporation have unveiled a novel approach to understanding how our metabolism during sleep influences fatigue recovery. This pioneering project was recently presented at the World Sleep Conference 2025 held in Singapore.

Background of the Research

With Japanese adults known to have some of the shortest sleep durations globally, interest in sleep quality has surged in recent years. Previous sleep research primarily relied on polysomnography (PSG) to analyze brain waves, eye movements, and various physiological metrics. However, there has been a notable gap in standardized evaluation methods assessing fatigue recovery, a critical aspect of sleep. This research aimed to bridge that gap by focusing on metabolic activity and energy expenditure during sleep, which are vital indicators of fatigue recovery.

While measuring metabolism through respiratory gas analysis, primarily used in sports science, has been common, its application in sleep studies has been minimal. By applying these methods in their research, this project stands as a pioneering effort to objectively evaluate fatigue recovery during sleep.

Overview of the Study

Led by Professor Shima Okada of the School of Science and Engineering at Ritsumeikan University, this research focuses on how the design features of Inoac's flagship product, the FACET® mattress, influence sleep metabolism. The research team utilized specialized equipment to monitor metabolic rates by analyzing the exhaled breath of participants. Subjects experienced two conditions: one with the hexagon slit feature of the FACET mattress and another without. PSG was employed to measure sleep depth, and additional parameters, like body movements, were also tracked.

Results and Analysis

The study categorized sleep into REM (Rapid Eye Movement) and non-REM stages. During REM sleep, the body is immobile while the brain is active, whereas non-REM sleep, particularly the deeper stages, plays a crucial role in effective fatigue recovery. Specific findings emerged during the trials conducted:

1. Reduced Metabolic Rate During Low Activity Sleep: It was determined that in conditions with less body movement, metabolic rates were significantly lower, indicating more effective rest. In deeper sleep stages (N3) and REM, where the body remains relatively still, minimal muscle activity is noted. Typically, increased muscle activity correlates with elevated metabolism. The FACET condition demonstrated a decreased metabolic rate compared to the unprocessed mattress, suggesting efficient posture maintenance requires less muscle action.

2. Efficient Rolling Movements: Analysis also revealed that even during increased physical transitions like rolling over, metabolism remained lower in the FACET condition compared to the unprocessed condition during the lighter sleep stages (N2). Post-analysis indicated that while metabolism temporarily spikes after rolling, it rapidly normalizes, demonstrating efficient rolling patterns that do not disrupt sleep.

These results suggest that the hexagon slit design of the FACET mattress optimizes metabolic activity during rest, leading to efficient recovery from fatigue.

Presentation Overview

- Conference: World Sleep 2025 (Singapore)
- Title: Proposal of a Novel Sleep Evaluation Index Utilizing Metabolic Dynamics During Sleep
- Format: Poster Presentation
- Date: September 7, 2025
- Presenter: K. Oyama (PhD candidate, Ritsumeikan University)

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Color Foam, established in 1959, represents Inoac's commitment to producing Japan's first urethane foam mattresses. The brand has remained steadfast in its dedication to integrated material development and manufacturing.

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Inoac Corporation, a pioneer in urethane foam production in Japan, leads in innovative materials and solutions across automotive, IT, construction, and everyday consumer products. Our expertise in polymer science allows us to develop high-performance materials that enhance everyday life.

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