Avoiding the Wall: Continuous Glucose Monitoring for Long-Distance Running

Shana Spindler PhD
Shana Spindler PhD
June 9, 2021

Garrett Panno was approaching mile 13 when he hit the dreaded “wall,” marathon lingo for a point when runners feel they simply can’t go on. It was a clear-sky October day in Chicago, and Panno had just raised over $1,800 dollars for the American Diabetes Association, with a promise to run the 2017 Chicago Marathon. Over a million spectators were cheering him on, but Panno’s blood sugar levels were dangerously high. Glancing at the numbers on his Continuous Glucose Monitor (CGM) made him question if he should continue. It wasn’t looking good.

Panno’s day began at 3:45 in the morning in a small Chicago hotel room. Donning his sleeveless, white Team Diabetes running shirt, Panno was eager to complete his first marathon. Many people would be surprised to learn that less than a year earlier, Panno, a Type 1 diabetic, hated running. It wasn’t until a few weeks after using CGM that he decided to chase a goal of marathon distance racing.

CGM has become a boon for endurance athletics, given that every athlete’s body responds differently to exercise. CGMallows individuals to monitor how their blood sugar levels respond to physical exertion and adjust carbohydrate intake on the fly. Carbohydrates, found ingrains, fruits, and vegetables, provide the body with glucose, a sugar that muscles extract from the blood to generate the energy needed to power muscle contractions.

Panno had been living with Type 1 diabetes for over a decade and was familiar with the interplay between blood glucose levels and insulin, the hormone needed to help cells uptake glucose from the blood—also the hormone that people with Type 1 diabetes lack. Because his body would continuously use precious glucose during the marathon, Panno was nervous that his insulin pump would cause low blood sugar, a potentially dangerous condition called hypoglycemia. Panno left his insulin pump in a pack on his bed and headed out to the race.

Everyone’s glucose metabolism is different during long distance running

About 16 years ago, a small study in Vienna, Austria, found marked variability in blood glucose levels during and after endurance races in five insulin-managed diabetic long-distance runners. Participants exhibited varying periods of low and high blood sugar levels while running, and continuous monitoring even revealed a participant who developed high blood sugar in the night following the marathon.

Concerns about blood sugar levels during exercise are not limited to individuals with diabetes. Case studies using CGMin elite runners and athletes of different training status have shown that non-diabetic athletes also show striking variability in glucose metabolism during long distance runs.

By mile five of the Chicago marathon, Panno realized that he needed his trusted insulin pump. Every check of his CGM showed his blood sugar levels were climbing. He admits that if he had stopped at a health station for glucose monitoring, he could have been pulled from the race.But he didn’t want to drop out. He wanted to finish.

Hitting a “brick wall” from high blood glucose levels

Panno’s insulin pump was sitting in his hotel room because he was afraid of low blood sugar during the marathon. But in his attempt to avoid hypoglycemia, he developed hyperglycemia, a condition in which blood sugar levels are too high.

Hyperglycemia is the very reason people with diabetes must closely monitor blood sugar. Without enough insulin, glucose in the blood rises to unsafe levels. Early symptoms of hyperglycemia include increased thirst, blurred vision, frequent urination, and headache. Eventually, hyperglycemia can lead to rapid heartbeat, confusion, and coma. Long distance runners typically don’t worry about hyperglycemia given the demands by their muscles for glucose, but with every stride, Panno felt fatigue, stiffness, and cramping.

After Panno hit the wall at 13 miles, he suffered through the remaining distance, carefully balancing his intake ofGatorade and water. “That first race was such a train wreck,” Panno admitted.

To prepare for his next marathon, Panno focused on strict glucose control. He identified the training and nutrition strategies that worked for him using data he collected from his CGM. One year later, he improved his marathon time by 30 minutes.

Fuelling for a long-distance run

A chiropractor by training, Panno’s experiences with glucose monitoring inspired him to pursue a Master’s degree inHuman Nutrition and Functional Medicine. He wants others to understand the benefits of monitoring blood sugar, even for non-diabetics. In particular, he emphasizes the importance of maintaining consistent blood sugar levels, rather than cycling through frequent highs and lows.

For someone with diabetes, it’s a little more complicated. “Individuals with Type 1 diabetes might find low carb diets are better, but with long distance running that’s very hard to do,” Panno explains. “CGM allows you to increase your carbs—a standard of running—in a way that is efficient for running and allows you to have your blood sugar levels controlled.”

The same idea applies to runners without underlying conditions. Personalization is key. You can learn how to fuel for long-distance running by monitoring how your blood sugar levels react to food and exercise.

Individualised information is ideal, but several clinical trial studies have attempted to optimize guidance on carbohydrate intake prior to endurance training. A small clinical trial found that eating carbohydrates 15 minutes prior to exercise led to better endurance.While another clinical trial found that adding a carbohydrate-electrolyte liquid during exercise to a pre-exercise meal further improved endurance running performance.

Preventing hypoglycemia during endurance exercise

Maintaining optimal blood sugar levels is critical for high performing long-distance runners. While Panno experienced about of hyperglycemia during his first marathon, for many long-distance runners hypoglycemia is the main concern. CGM can help runners understand how their individual bodies respond to physical exercise, revealing if they are prone to hypoglycemia during endurance events.

According to the American Diabetes Association, their “15-15 rule” can help individuals—in particular those with diabetes—regulate blood glucose levels during exercise. If your blood sugar level is below 100mg/dL, eat 15 grams of carbohydrates and retest after 15 minutes, their guidance explains, repeating this process until blood sugar levels read at least 100 mg/dL.

As for continuing to use CGM in his racing endeavors, Panno doesn’t plan to stop anytime soon. “I’ve never run a race without it, and I don’t think I ever will,” he says.  

References:

Low Blood Glucose (Hypoglycemia)

Continuous glucose monitoring in diabetic long distance runners

Continuous glucose monitoring during a 100-km race: a case study in an elite ultramarathon runner

Different training status may alter the continuous blood glucose kinetics in self-paced endurance running

Hyperglycemia(High Blood Sugar)

Effects of carbohydrate ingestion 15 min before exercise on endurance running capacity

The effect of a high carbohydrate meal on endurance running capacity

Getting Started Safely Blood Sugar and Exercise

Garrett Panno was approaching mile 13 when he hit the dreaded “wall,” marathon lingo for a point when runners feel they simply can’t go on. It was a clear-sky October day in Chicago, and Panno had just raised over $1,800 dollars for the American Diabetes Association, with a promise to run the 2017 Chicago Marathon. Over a million spectators were cheering him on, but Panno’s blood sugar levels were dangerously high. Glancing at the numbers on his Continuous Glucose Monitor (CGM) made him question if he should continue. It wasn’t looking good.

Panno’s day began at 3:45 in the morning in a small Chicago hotel room. Donning his sleeveless, white Team Diabetes running shirt, Panno was eager to complete his first marathon. Many people would be surprised to learn that less than a year earlier, Panno, a Type 1 diabetic, hated running. It wasn’t until a few weeks after using CGM that he decided to chase a goal of marathon distance racing.

CGM has become a boon for endurance athletics, given that every athlete’s body responds differently to exercise. CGMallows individuals to monitor how their blood sugar levels respond to physical exertion and adjust carbohydrate intake on the fly. Carbohydrates, found ingrains, fruits, and vegetables, provide the body with glucose, a sugar that muscles extract from the blood to generate the energy needed to power muscle contractions.

Panno had been living with Type 1 diabetes for over a decade and was familiar with the interplay between blood glucose levels and insulin, the hormone needed to help cells uptake glucose from the blood—also the hormone that people with Type 1 diabetes lack. Because his body would continuously use precious glucose during the marathon, Panno was nervous that his insulin pump would cause low blood sugar, a potentially dangerous condition called hypoglycemia. Panno left his insulin pump in a pack on his bed and headed out to the race.

Everyone’s glucose metabolism is different during long distance running

About 16 years ago, a small study in Vienna, Austria, found marked variability in blood glucose levels during and after endurance races in five insulin-managed diabetic long-distance runners. Participants exhibited varying periods of low and high blood sugar levels while running, and continuous monitoring even revealed a participant who developed high blood sugar in the night following the marathon.

Concerns about blood sugar levels during exercise are not limited to individuals with diabetes. Case studies using CGMin elite runners and athletes of different training status have shown that non-diabetic athletes also show striking variability in glucose metabolism during long distance runs.

By mile five of the Chicago marathon, Panno realized that he needed his trusted insulin pump. Every check of his CGM showed his blood sugar levels were climbing. He admits that if he had stopped at a health station for glucose monitoring, he could have been pulled from the race.But he didn’t want to drop out. He wanted to finish.

Hitting a “brick wall” from high blood glucose levels

Panno’s insulin pump was sitting in his hotel room because he was afraid of low blood sugar during the marathon. But in his attempt to avoid hypoglycemia, he developed hyperglycemia, a condition in which blood sugar levels are too high.

Hyperglycemia is the very reason people with diabetes must closely monitor blood sugar. Without enough insulin, glucose in the blood rises to unsafe levels. Early symptoms of hyperglycemia include increased thirst, blurred vision, frequent urination, and headache. Eventually, hyperglycemia can lead to rapid heartbeat, confusion, and coma. Long distance runners typically don’t worry about hyperglycemia given the demands by their muscles for glucose, but with every stride, Panno felt fatigue, stiffness, and cramping.

After Panno hit the wall at 13 miles, he suffered through the remaining distance, carefully balancing his intake ofGatorade and water. “That first race was such a train wreck,” Panno admitted.

To prepare for his next marathon, Panno focused on strict glucose control. He identified the training and nutrition strategies that worked for him using data he collected from his CGM. One year later, he improved his marathon time by 30 minutes.

Fuelling for a long-distance run

A chiropractor by training, Panno’s experiences with glucose monitoring inspired him to pursue a Master’s degree inHuman Nutrition and Functional Medicine. He wants others to understand the benefits of monitoring blood sugar, even for non-diabetics. In particular, he emphasizes the importance of maintaining consistent blood sugar levels, rather than cycling through frequent highs and lows.

For someone with diabetes, it’s a little more complicated. “Individuals with Type 1 diabetes might find low carb diets are better, but with long distance running that’s very hard to do,” Panno explains. “CGM allows you to increase your carbs—a standard of running—in a way that is efficient for running and allows you to have your blood sugar levels controlled.”

The same idea applies to runners without underlying conditions. Personalization is key. You can learn how to fuel for long-distance running by monitoring how your blood sugar levels react to food and exercise.

Individualised information is ideal, but several clinical trial studies have attempted to optimize guidance on carbohydrate intake prior to endurance training. A small clinical trial found that eating carbohydrates 15 minutes prior to exercise led to better endurance.While another clinical trial found that adding a carbohydrate-electrolyte liquid during exercise to a pre-exercise meal further improved endurance running performance.

Preventing hypoglycemia during endurance exercise

Maintaining optimal blood sugar levels is critical for high performing long-distance runners. While Panno experienced about of hyperglycemia during his first marathon, for many long-distance runners hypoglycemia is the main concern. CGM can help runners understand how their individual bodies respond to physical exercise, revealing if they are prone to hypoglycemia during endurance events.

According to the American Diabetes Association, their “15-15 rule” can help individuals—in particular those with diabetes—regulate blood glucose levels during exercise. If your blood sugar level is below 100mg/dL, eat 15 grams of carbohydrates and retest after 15 minutes, their guidance explains, repeating this process until blood sugar levels read at least 100 mg/dL.

As for continuing to use CGM in his racing endeavors, Panno doesn’t plan to stop anytime soon. “I’ve never run a race without it, and I don’t think I ever will,” he says.  

References:

Low Blood Glucose (Hypoglycemia)

Continuous glucose monitoring in diabetic long distance runners

Continuous glucose monitoring during a 100-km race: a case study in an elite ultramarathon runner

Different training status may alter the continuous blood glucose kinetics in self-paced endurance running

Hyperglycemia(High Blood Sugar)

Effects of carbohydrate ingestion 15 min before exercise on endurance running capacity

The effect of a high carbohydrate meal on endurance running capacity

Getting Started Safely Blood Sugar and Exercise