Research on the Effects of the Thermal Charge Design, Which Efficiently Warms and Retains Heat in the Muscles, on Sleep
In Japan, the percentage of people who report getting adequate rest from sleep has fallen below 80%, making the improvement of sleep quality an increasingly important issue. In recent years, body temperature regulation and physiological rhythms at the time of falling asleep have been recognized as key factors in improving sleep quality. In particular, sleepwear, which directly affects skin temperature and perspiration, is attracting attention alongside bedding.
At Mizuno, we have been applying our expertise and know-how as a comprehensive sporting goods manufacturer to the field of sleep, guided by the concept of “Making Sleep More Comfortable Through Sports Technology,” with the aim of improving sleep performance for everyone.
In this study, we conducted joint research with Professor Ryoma Michishita of the Faculty of Sports and Health Science at Fukuoka University to verify the effects of Mizuno’s Thermal Charge Design wear, which efficiently warms the muscles, on sleep measurements and physiological responses.
Thermal Charge Design (a design using heat-generating material only in major muscle areas)
Purpose of the Joint Research and the Co-creation Process
“Warming before and around sleep onset promotes a drop in core body temperature during sleep, leading to improved sleep quality,” (Kräuchi K, et al. Nature, 1999). We were inspired by the findings reported by Kräuchi K, et al. The purpose of this study was to clarify what effects Mizuno’s Thermal Charge design, which efficiently retains warmth in the muscles, has on sleep quality and physiological responses. As with our previous joint research verifying the effects of the Mizuno mattress on sleep, this co-creation was carried out with Professor Ryoma Michishita of the Faculty of Sports and Health Science at Fukuoka University, based on the partnership and cooperation agreement between Mizuno and Fukuoka University.
Research on the Effects of the Mizuno Physical Support Mattress (Prototype) on Sleep
Research Overview
In this study, 12 healthy young men without sleep disorders participated in a residential experiment lasting 2 nights and 3 days for each condition. Participants wore either standard warm-up pants or Mizuno Thermal Charge warmer pants, which feature Breath Thermo material placed along major superficial muscles of the lower body, including the quadriceps, gastrocnemius, and hamstrings. In addition to objective measures such as electroencephalography (EEG) and core body temperature, sleep quality assessments evaluating subjective measures, sleep quality upon waking, and mood upon waking were also measured and evaluated.
Experimental Results
When wearing the Mizuno Thermal Charge Design pants, sleep onset latency tended to be shorter compared to wearing standard warm-up pants. This is thought to be related to the thorough warming of the lower limbs before sleep and to changes observed in melatonin secretion. In addition, while the body was kept warm before sleep, skin temperature and core body temperature showed a marked tendency to decrease during sleep, and it was confirmed that heat dissipation occurred more efficiently during sleep. Furthermore, scores from the OSA-MA Sleep Inventory, which evaluates perceived sleep quality upon waking, showed clear differences in mood upon waking and perceived sleep quality. The Profile of Mood States Second Edition (POMS2) psychological test that measures mood immediately after waking also showed favorable trends for the Mizuno Thermal Charge Design in post-waking mood and overall condition.
Joint Research Outcomes
The experimental results indicated that warmer pants incorporating the Mizuno Thermal Charge Design may be more effective than standard warm-up pants not only in terms of perceived sleep quality, but also in post-waking mood and condition. In other words, sleepwear can serve not only a comfort role at bedtime, but also a functional role in guiding the wearer toward better sleep. These results also suggested a connection between Mizuno Thermal Charge Design warmer pants and everyday condition.
Sleep EEG
Salivary Melatonin Concentration
Pre-Sleep Skin Temperature, Core Body Temperature, and Changes
Profile of Mood States (POMS 2)
Presenting Joint Research Outcomes at Academic Conferences
In July 2026, the findings of this joint research were presented at the Japanese Society of Sleep Research Annual Meeting. We will continue to widely share the results of our verification of sleep while wearing Mizuno Thermal Charge Design warmer pants, with Breath Thermo material placed along major superficial muscles of the lower body including the quadriceps, gastrocnemius, and hamstrings, based on objective data.
Sleep deprivation is known to lead not only to reduced daytime performance and low mood, but also to long-term health risks.
In an age referred to as the era of 100-year lifespans, Mizuno views sleep as just as important as physical exercise. We will continue to provide sleep support products toward the realization of “Making Sleep More Comfortable Through Sports Technology,” so that everyone can sustain healthy performance around the clock.
Research on the physiological effects of apparel design that keeps muscles warm efficiently
