This post was co-written with Dr. Steven E. Riechman, Associate Professor at Texas A&M University.

Dr. Riechman received his Ph.D. in Exercise Physiology, MPH in Epidemiology, and Post-Doctoral Fellowship in Human Genetics at the University of Pittsburgh. He joined the Health and Kinesiology Department at Texas A&M University as an Assistant Professor in 2005, where he teaches Applied Physiology and Nutrition. As Division Chair of Kinesiology, he overhauled the undergraduate curriculum in 2018 and developed the Dual Masters in Kinesiology and Nutrition. His research on human performance and fatigue has attracted over $5 million in funding from the Department of Defense (DARPA), National Institute of Health and the National Science Foundation. He’s published 55 peer-reviewed journal articles, chaired 35+ committees, served on 100+, and mentored numerous students. He received the Genesis Award in 2023 and the Senior Scholar Research Excellence Award in 2024.

​Symptoms of fatigue can include trouble focusing, low mood, depression, muscle pain, and more, which can severely impact someone’s day-to-day life.

The symptoms and outcomes of fatigue are then amplified when someone in a high stakes environment, such as a soldier, airman, astronaut, or industrial worker, experiences it. Not only will fatigue be induced more quickly, but the consequences in some cases can be fatal.

This led Dr. Steven E. Riechman, Associate Professor at Texas A&M University, to examine physical fatigue, sleep deprivation fatigue, and mental fatigue of subjects, working alongside the US Department of Defense. He aimed to identify thresholds for intervention, so people could be pulled out of environments when they met the fatigue threshold that would put themselves and others at high risk.

Another area of interest for Riechman is the mitigation of fatigue. He said, “With biomarkers of fatigue, we can examine the mechanisms of fatigue and develop mitigation strategies to delay fatigue. Obviously, it's impossible to prevent fatigue altogether, but you can help to mitigate it, and sustain a high level of performance to keep people safe”.

Identifying breath biomarkers of fatigue

The primary objective of the study was to identify breath biomarkers of fatigue. Riechman said, “The breath biomarkers are the primary aim because those would be novel biomarkers of fatigue. A secondary and important aim of the study is developing prediction models for fatigue”.

He went on to say, “Breath Biomarkers is an emerging field to detect changes in physiological state that is particularly interesting because of the opportunity to assess and monitor these states in real time and importantly non-invasively”.

The study combined real-world and lab data, with over 80% wear time during the 7 weeks

Riechman and his team conducted the study with 60 subjects from the Department of Defense split into seven cohorts. Empatica’s EmbracePlus wearable was worn by each participant for a 7-week duration, and the full study was conducted over 15 months.

The subjects were healthy and fit males and females aged 18-30. They completed 5 fatigue trials over the 7 week period. The first two weeks were baseline physiological parameters using wearables.

The 5 fatigue trials were all laboratory-based interventions designed to cause maximal fatigue. Physical fatigue trials included spending 2 hours on the treadmill, carrying 40% of their body weight in a rucksack, and moving at the maximum sustainable speed. Mental fatigue trials involved completing a mental task on the computer for 2 hours, and sleep deprivation fatigue involved spending 30 hours awake continuously.

Riechman said, “Having just completed the study, we are highly focused on validating the breath biomarkers of fatigue using high-quality laboratory measures of fatigue. Subsequent analyses will dive deeper into characterizing the nature of fatigue and developing predictive models that utilize mobile indicators of physiological state”.

He went on to say, “Our summary data shows that EmbracePlus achieved a wear time of over 80% during the 7 weeks”.

The benefits of using EmbracePlus: Raw data and FDA validation

Riechman felt that wearable technology was essential for this study: “In order to monitor fatigue, we need continuous information in various settings. Having mobile measures and the algorithms associated with them is essential to capturing fatigue when it's occurring. So wearable technology is essential”. Riechman and his colleague Dr. Roozbeh Jafari, a principal staff member in the Biotechnology and Human Systems Division at MIT Lincoln Laboratory, decided to use Empatica’s technology for two main reasons - FDA clearance and the raw data available.

Riechman said, “I really liked that EmbracePlus and the Empatica Health Monitoring Platform are focused on clinical trials and are FDA-cleared. That represents a higher standard, whereas off-the-shelf commercial devices aren't necessarily held to the same standards”.

In addition, Riechman was interested in the raw data that Empatica provides: “This is an emerging area, so there's a lot of opportunities for getting novel insights from raw data that conditioned data does not provide. With wearable technology, the provider can apply their own algorithms that perhaps smooth data. We want the opportunity to challenge assumptions of a standardized algorithm and don't want to have to question whether data is artificially altered”.

The largest breath and fatigue study ever done

The experimental part of this study was recently completed by Riechman and his team: “We're highly focused on the primary aims and the gold standards of fatigue and we have what I would consider fantastic data in that regard”.

“We're sorting through the identification of novel biomarkers, building those biomarker models, and identifying thresholds of fatigue or levels of fatigue. It’s a very challenging field to define those really well, but that work is going to be critical to come back to the wearable data and identify what we're observing with the laboratory data and how that feeds that”.

“I'm extraordinarily proud of what our team accomplished. We completed this study in 15 months. I think under normal conditions, it would have been a 3+ year study to conduct this, considering the size and complexity. As far as I’m aware, it's the largest fatigue and largest breath study ever done”.

Looking ahead

Looking to the future, Riechman is interested in examining motion: “When individuals are getting physically fatigued, their motor control can decline and identification of a wearable signal that indicates or red flags fatigue would be good. Motion capture is a very precise gold standard that we can do in the lab”.

When asked what advice Riechman would give to researchers interested in incorporating wearable technology into their work, he said: “I think one of the things that I appreciated going into this was having a very specific objective in using the technology. The volume of data that is acquired requires some expertise and a specific objective to help examine”.

Thank you to Dr. Steven Riechman for your contribution. We look forward to seeing the full results in the near future.

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