Inside the Heat Lab: Studying the Human Cost of Extreme Temperatures

At the heart of the University of Connecticut's Korey Stringer Institute (KSI) is a state-of-the-art heat lab, pushing the boundaries of what is known about the human body under extreme heat stress. As global temperatures continue to climb and climate change accelerates, this lab is helping scientists, athletes, workers, and policymakers understand just how dangerous heat can be—and how we can better protect people in real-world conditions.

In a recent deep-dive feature by The New York Times, a reporter stepped into the heat lab, strapped into biometric monitors, and underwent a simulated workout under rising temperatures. The goal was to observe the effects of heat on the body in real time and better understand how hydration, cooling strategies, and environmental conditions influence safety and performance.

A Living Laboratory for a Hotter World

The Korey Stringer Institute was named in memory of NFL player Korey Stringer, who died from exertional heatstroke during training camp in 2001. Funded in part by a settlement from the Stringer family and the NFL, the institute was created to investigate the root causes of heat-related illness and to improve prevention strategies across sports, military, and occupational environments.

Today, KSI operates with a dual mission: advancing heat-safety science for athletes while expanding its reach into high-risk professions such as construction, agriculture, warehousing, delivery driving, and military service. Following a recent expansion, the facility can now study a broader range of individuals and simulate more complex occupational heat-stress scenarios.

KSI's work is grounded in translating science into practice—helping employers, safety professionals, and policymakers understand when heat becomes dangerous and what actions are needed to prevent injury or death.

Simulating Extreme Heat in Real Time

At first glance, the lab resembles a typical gym, complete with treadmills, stationary bikes, and water bottles. But closer inspection reveals a highly controlled environment designed to replicate real-world heat exposure. Researchers can precisely manipulate air temperature, humidity, radiant heat, and airflow, with conditions ranging from -20°F to 120°F and humidity levels from 20% to 90%.Environmental heat stress in the lab is quantified using Kestrel Heat Stress Trackers that measure Wet Bulb Globe Temperature (WBGT), which captures the combined effects of temperature, humidity, radiant heat, and wind—factors that directly influence the body's ability to cool itself. WBGT is widely used in occupational safety standards and heat-stress research because it reflects how heat is actually experienced by the human body during physical work.

In the New York Times test, the reporter completed two trials: one at 70°F with 60% humidity and another at 92°F with the same humidity, replicating real sidewalk heat readings recorded in New York City. Throughout both tests, researchers monitored core body temperature, heart rate, cognitive performance, and perceived exertion.

Heat's Impact on the Body

One of the most striking findings was how quickly the body responded to heat stress. During the high-heat trial, the reporter experienced rapid sweating and a sharp increase in heart rate. With close supervision, strict safety protocols, and emergency cooling options such as cold-water immersion, researchers ensured there was no risk of serious illness.

The lab routinely monitors for warning signs of heat exhaustion and heat stroke, including dizziness, confusion, and core body temperatures exceeding 104°F. What makes KSI unique is its ability to safely push participants close to these physiological limits in a controlled environment, allowing researchers to understand where tipping points occur.

As Dr. Rebecca Stearns, KSI's COO, has explained, once core body temperature approaches 106°F, the body begins to experience cellular damage and cognitive impairment—conditions that can quickly become fatal without rapid intervention.

Hydration Makes All the Difference

One of the most important insights from the experiment was unintentional. The reporter arrived at the lab already dehydrated, which affected the results of the cooler-temperature trial. Despite the lower ambient temperature, their core body temperature rose to 101.3°F—higher than during the later, hotter test.

After rehydrating between trials, the reporter's core temperature during the 92°F test peaked at just 100.9°F. This reversal underscored a critical lesson: dehydration significantly impairs the body's ability to regulate heat, even in moderate conditions. Heat illness risk can rise long before workers or athletes perceive conditions as “extreme.”

Measuring and Managing Heat Stress in the Real World

The research conducted at KSI informs how heat stress is measured and managed outside the lab. Tools such as WBGT monitoring devices allow safety teams to move beyond basic temperature readings and assess true environmental heat load.

Kestrel Heat Stress Trackers and WBGT meters are commonly used in occupational, athletic, and military settings to measure these conditions in real time. Kestrel has been a long-time partner of the Korey Stringer Institute, supporting heat-safety research and helping translate lab-based findings into practical tools that can be deployed in the field. By combining environmental monitoring with evidence-based thresholds, organizations can make informed decisions about work-rest cycles, hydration schedules, and cooling interventions before workers reach dangerous levels of heat strain.

Cooling Strategies That Work

The lab doesn't just study heat—it rigorously evaluates ways to reduce its impact. Participants rotate through cooling interventions such as ice-cold towels, immersion baths, shaded rest periods, and structured breaks.

Across both cooler and hotter scenarios, researchers observed that body temperatures dropped during cooling breaks and rose more slowly afterward. These findings reinforce a key principle of heat safety: regular rest and cooling are not optional; they are essential controls for reducing risk during high-heat activity.

Understanding Real-World Occupational Risk

KSI's work extends well beyond athletics. The institute has partnered with major organizations, including UPS, Delta Air Lines, and the U.S. Department of Defense, to study heat stress in occupational environments such as warehouses, delivery routes, and aviation operations.

The lab has also contributed research supporting OSHA's proposed federal heat standard, which would require employers to implement hydration, rest, and shade protocols when heat reaches dangerous levels. Many of these recommendations—such as designated cooling stations and proactive heat monitoring—are already being adopted by forward-thinking employers.

Not Just for Athletes

Although KSI began with a focus on sports, its research now emphasizes broader populations. Military personnel carrying heavy gear, agricultural workers laboring in direct sun, and warehouse employees working long shifts all face elevated heat risk.

To reflect these realities, the lab incorporates simulations such as box-lifting rigs and load-bearing tasks to replicate occupational work. These scenarios provide critical insight into how heat stress develops during real jobs—not just athletic training.

Even in unexpected settings, heat strain can be severe. In sports like hockey, for example, goalies can lose up to three liters of fluid per hour despite playing on ice. The takeaway is clear: any physically demanding activity can become dangerous under the right heat conditions.

Beyond the Data: The Human Cost

The death of Korey Stringer remains a powerful reminder of the stakes involved. Heat illness is preventable, yet it continues to claim lives when warning signs are missed or conditions are underestimated.

With more than 400 peer-reviewed publications, the Korey Stringer Institute continues to shape national policy, occupational safety guidance, and athletic standards. As extreme heat becomes more frequent and intense, this work is no longer optional—it is urgent.

What This Research Means for the Future

The research emerging from KSI's heat lab is practical, actionable, and increasingly necessary. From hydration and cooling strategies to WBGT-based monitoring and federal safety standards, the science is helping define how we protect people in a hotter world.

As global temperatures rise, understanding and managing heat stress will be essential to safeguarding athletes, workers, and entire industries. Through partnerships between research institutions like KSI and technology providers such as Kestrel, science is being translated into tools and practices that can save lives—before heat becomes deadly.