Here's What Happened When Gatorade Sent Me to Train Outdoors in the Brutally Cold Minnesota Winter

For Gatorade's 'G Sweat School' event, I worked out in extreme cold while scientists with cutting-edge technology analyzed my body's response.

When Gatorade invited STACK to their "G Sweat School" event in Minneapolis ahead of Super Bowl LII, I thought I was in for a breezy little event.

Run around a little bit, drink some Gatorade, interview some experts from their Sports Science Institute, grab a Juicy Lucy and head back to the airport. When I found myself unable to feel my fingers while running Parachute Sprints in temperatures barely hovering above zero, I quickly realized I was wrong.


When Gatorade invited STACK to their "G Sweat School" event in Minneapolis ahead of Super Bowl LII, I thought I was in for a breezy little event.

Run around a little bit, drink some Gatorade, interview some experts from their Sports Science Institute, grab a Juicy Lucy and head back to the airport. When I found myself unable to feel my fingers while running Parachute Sprints in temperatures barely hovering above zero, I quickly realized I was wrong.

The night before the event, I was in my hotel room staring at the biggest pill I'd ever been asked to swallow in my life. Why so large? Because this was no normal pill—this was a CorTemp Ingestible Core Body Temperature Sensor. It's one of the many tools researchers at the Gatorade Sports Scientist Institute (GSSI) use to monitor the health and hydration of elite athletes. The pill transmits a harmless low-frequency signal that informs researchers of an athlete's exact core temperature to within 0.1 degree Celsius. Thermometers under the tongue are so passé, and they often provide readings a bit lower than the body's true core temperature.

The CorTemp sensor is the most accurate tool GSSI has for measuring an athlete's core temperature, which is very important in the world of sports science (more on that later). The sensor is typically passed within 24-36 hours after ingestion, which is why I was asked to take it directly prior to bedtime the night before the event. I downed the sensor with a big gulp of water, set my alarm for 5 a.m., and drifted off to dream land.

The CorTemp Ingestible Core Body Temperature Sensor

I arrived at the Colin Powell Community Center the next morning at 6 and quickly underwent a battery of tests and measurements. I was scanned to make sure the sensor was still inside my body. I was stripped down to my tights and weighed and told not to consume any water or food without notifying someone first. I was photographed with a thermal camera that detected the skin temperature over the surface of my body. I was asked to rate my thirstiness, comfort and rate of perceived exertion. All these measures were going to help the GSSI scientists figure out exactly how my body handled the extreme training conditions it was about to endure.

Take sweat rate, for example. It's simply a measure of how many liters of sweat an athlete loses per hour. But to accurately calculate sweat rate, GSSI scientists must control every possible variable. Every time I weighed in, I had to be wearing the exact same amount of clothing (in this case, nothing more than tights). Everything that came in or out of my body had to be accounted for. We were provided with two personal bottles of Gatorade and water which were weighed before and after every session. I peed right after my initial weigh-in, so I had to weigh in again. When I ate half of a Gatorade Whey Protein Bar, the crew made sure I gave them the remaining half so they could calculate exactly how many grams I ingested. One GSSI scientists told me he's weighed "everything that could possibly come out of a human body" at one point or another, and it's all in an effort to calculate the most accurate sweat rate possible.

Once all the participants were suited up and measured in, we prepared to head out into the elements. Dr. James Carter, the Director of GSSI, later offered an outline of the morning's events.

"The Gatorade Sweat School is, in essence, about creating two scenarios—a scenario exercising in the extreme cold, and a scenario exercising in the heat. With the intent of comparing the participants' perceptual and also physiological responses to both scenarios and (seeing) how nutrition can impact those responses." After a pre-workout pep talk from our personal trainer Anthony "Spice" Adams—the former NFL defensive tackle turned social media personality—we ventured outside on a January morning in eastern Minnesota.

It was about 6 minutes into the warm-up jog when I realized I was in trouble. My fingers—gloveless due to my own ignorance—were rapidly losing feeling. The freezing air seemed to get colder with every breath. Things improved slightly as we began the actual workout, which consisted of exercises like Resisted Sprints, Split-Squat Jumps and Med Ball Slams. A friendly bystander offered me a pair of gloves, which I gladly pulled on before shoving two hand warmers inside each mitt. But the initial adrenaline of intense exercise soon gave way to the misery of being outside during the coldest part of the day during one of the coldest months in one of the most harshest cities in America. I went hard during every drill, but I barely touched the Gatorade and water which were available during breaks. My "thirst" rating actually went from "thirsty" during the pre-activity screening, to "neutral" during the activity, to "not thirsty" post-activity. It seems counterintuitive, but the extreme cold can really hamper your desire for fluids.

"A blunting of the thirst response is very common in the cold," Carter says. Hydration is one of the biggest challenges elite athletes face in extremely cold weather.

Most people drink less fluids during the winter months, which exacerbates a common issue which plagues many athletes—coming into activity already under-hydrated. "(One common problem we see when we analyze athletes) is hydration status before they start a session—so before a practice or a game. One thing we do is get a hydration assessment just from a small urine sample. And from that sample we're able to tell how hydrated they are. When we do test athletes, it's not uncommon to see they're already in a minimally dehydrated, or a dehydrated state completely, before they start (activity)," GSSI Senior Scientist Khalil Lee tells STACK.

After roughly 25 minutes outdoors, with the entire training group seemingly at risk of turning into the White Walkers from Game of Thrones, we headed back inside. We were then run through the same battery of tests and measurements we were subjected to earlier as our extremities thawed in preparation for the indoor workout. While that turned out to be a much more comfortable affair in terms of climate, the training itself was also more fierce.

We entered a small group workout room on the second floor to find a space heater running in the corner. The room wasn't stifling hot, but the temperature—which was somewhere in the mid to high 70s—was a stark contrast to the biting outdoor air. Once the workout began, we really got after it. Everything was done in circuit fashion, and we hit all the exercises you love to hate—Bear Crawls, Burpees, jump rope, Planks, you name it. Despite Spice's words of "encouragement," I was drained by the end of the session. My rate of perceived exertion at the end of the indoor workout was "really hard" compared to "somewhat hard" for the outdoor workout, and my thirst rating was "very thirsty" compared to "not very thirsty." Consider this—during the outdoor workout, my sweat rate was 0.2 liters per hour. Indoors, it was 0.9 liters per hour. That's a pretty serious leap.

My core temperature also showed a marked difference, as I was at about 101.5 degrees Fahrenheit after the indoor workout compared to 99.7 after the outdoor workout. The report given to me by GSSI after the workouts also detailed an estimated "time to core temp 39.5 degrees Celsius." For the outside workout, it was 218 minutes (meaning if I had worked out at the same intensity I did during the duration of the outdoor workout for 218 minutes, my core temp would end up at about 39.5 degrees Celsius). For the indoor workout, it was 64 minutes—so more than three times shorter. Why was 39.5 degrees Celsius the marker? Though there's been some debate about it, that number is often regarded as a sort of "critical core temperature." Meaning once you hit it, you're going to experience some serious symptoms that will make you want to stop exercising. The body wants to keep your core temperature around 37.2 degrees Celsius, so a two-degree increase is quite significant.

"Core temperature is one measure that our body is really striving to tightly regulate. About 37.2 to 37.5 degrees Celsius—that's the range your body is going to fight to keep it in," Lee says.

While it wasn't particularly humid in either workout condition, I did learn an interesting fact about why high humidity can make athletes feel so darn miserable. I always knew athletes sweat more in high humidity conditions, but I never really knew why. As Lee explained to me, it has to do with the atmosphere's ability to pull moisture off your skin. Our body uses sweat to cool itself off. As that sweat evaporates off our skin, it transfers our body's heat into the air. In normal conditions, this process does a great job of cooling off the body. But the rate at which that sweat evaporates into the air depends on how much moisture is already in the air. Humidity is defined as the amount of water in the atmosphere, so on days with high humidity, the air is already saturated with water. That means it takes much longer for the sweat to evaporate off your body (if it does at all), which throws a gigantic wrench into this natural cooling system.

Would I personally recommend training outside in January in Minnesota? Nope. But some athletes don't have a choice. The G Sweat School was all about learning how to optimize your body for various conditions through hydration and nutrition. When you find yourself in less-than-ideal conditions, what you put in is what you get out.

Photo Credit: Gatorade