出处 : bikeradar 作者 : Jack Evans
With the advancement of technology, continuous glucose monitoring (CGM) has become a part of health management for many people. But is this technology really worth trying for bike enthusiasts?
According to a variety of sources, real-time blood glucose monitoring technology provides endurance athletes with a new perspective that allows them to gain more precise insight into their carbohydrate needs to improve athletic performance.
However, the application of this technology in the field of sports is not without controversy. In particular, questions about its accuracy during exercise and whether non-diabetic patients really need to record blood glucose data have been the focus of questioning.
In order to delve deeper into this topic, foreign media interviewed a number of athletes and nutrition experts, and referred to a large number of scientific research data, hoping to provide a more comprehensive and objective perspective to evaluate the potential benefits of this technology for endurance athletes such as cyclists.
What is continuous glucose monitoring?
Continuous glucose monitoring is a technique that continuously monitors and records the user's blood glucose levels through sensors implanted under the skin, providing a comprehensive picture of blood glucose changes.
▲In general, maintaining stable blood glucose levels is crucial, but for athletes, blood sugar management is more complicated by changes in exercise intensity and energy requirements
Normally, the body maintains a stable blood sugar level through a sophisticated regulatory system to avoid the occurrence of hypoglycemia (hypoglycemia) and hyperglycemia (hyperglycemia).
In patients with type 1 diabetes, this regulatory system is compromised. Because their pancreas can't produce enough insulin, they need external means to monitor and manage their blood sugar levels.
Continuous glucose monitors (continuous glucose monitoring) are tools designed to meet this need.
Market status and technology application
▲Supersapiens was once in the limelight in the sports world and became the choice of many top athletes
Until March 2024, when the American brand Supersapiens stopped trading, its sensors became almost standard for cyclists competing on the World Tour. However, continuous glucose monitoring technology is not inexpensive. Most subscription services cost between £100 and £150 (or equivalent dollars) per month, which is a significant expense for the average consumer.
How does a continuous glucose monitor work?
▲The continuous glucose monitoring system consists of a blood glucose sensor that is responsible for sending data to a companion app, and sometimes the data is also synchronized to the user's wristband
To use this system, the user uses a device the size of a postage stamp, which is lightly attached to the skin, usually on the back of the upper arm.
In this procedure, a needle pierces the skin and then inserts a thinner filament. Once the needle has completed its mission, it automatically retracts, leaving the filamentous body under the skin to continuously measure glucose levels in the interstitial fluid. The interstitial fluid is an important medium for nutrient exchange between subcutaneous cells.
▲The sensor is securely attached to the skin with a small needle and adhesive patch
It is important to note that although the system assumes that the concentration of glucose in the interstitial fluid is equal to the concentration of glucose in the blood, in practice there is a certain lag between the two, which can cause problems in the state of exercise.
Once installed, a glue sheet will securely attach the sensor to your arm. Next, you'll need to pair the sensors with the built-in NFC chip with the app to wirelessly transmit data to your phone or bracelet via Bluetooth technology, with each sensor having a lifespan of about 14 days.
Do healthy athletes need continuous glucose monitoring?
▲ High efficiency of blood sugar regulation in healthy people
In people with diabetes, there are good reasons to use continuous glucose monitoring techniques, especially when they are exercising. Take Team Novo Nordisk, for example, a professional cycling team made up entirely of diabetics. They took full advantage of continuous glucose monitoring technology when they competed at the UCI Pro Team level.
In 2021, Supersapiens became the first company to promote continuous glucose monitoring technology to endurance athletes. They claim that monitoring blood sugar levels in real time can help athletes replenish energy more accurately, further improving performance and recovery. This is an attractive advantage for both diabetic and non-diabetic athletes.
Its effectiveness has not been proven, but it has been banned during the event
Later that year, the UCI made a decision to ban non-diabetic riders from using continuous glucose monitors in races. Explaining the ban, Mick Rogers of the Union Cycliste Internationale said: "Fans don't want to see cycling become too tech-savvy like Formula 1, they crave surprise and unpredictability. ”
▲ At the 2023 Stellar Bjarne Cycling Race, Christen Faulkner was disqualified from third place for using continuous glucose monitoring technology. The incident sparked widespread controversy about the use of continuous glucose monitoring in athletic competitions
▲Supersapiens claims that controlling blood sugar levels can improve exercise performance within a certain range
From personal experience, I tried the Supersapiens continuous glucose monitoring device for a month, and it is indeed easy to get the illusion that controlling blood sugar within a certain range can help enhance exercise performance. However, Flockhart and Larsen take a different view. They believe that for trained endurance athletes, they already have a fairly effective ability to regulate blood sugar during exercise.
These professional athletes are able to effectively use fat as an energy source when exercise intensity is low, thus keeping their blood sugar levels in the lower range than those who are not training. And when the intensity of exercise increases, their blood sugar will rise rapidly to meet the energy needed for muscle work.
Flawed indicators?
For endurance athletes, blood sugar may not be a particularly accurate or comprehensive measure of performance.
▲In fact, when an athlete is approaching the limit of exhaustion, there is a possibility that the blood sugar level of an athlete will rise sharply
As early as the 20s of the 20th century, there were studies linking the hypoglycemic status of marathon runners to fatigue. However, while hypoglycemia does serve as a predictor, it is not always an accurate predictor of endurance exercise failure. For example, an athlete's blood sugar levels may rise before high-intensity interval training can continue.
In addition, data from continuous glucose monitors show that endurance athletes often have greater blood sugar fluctuations than sedentary people. If these fluctuations are confirmed by follow-up studies to "negatively impact certain bodily functions of the athlete, such as recovery," then tracking blood sugar levels may become truly beneficial.
Glycogen is superior to glucose
▲ When it comes to energy supply for endurance exercise, some experts have suggested that glycogen, which is more abundant, actually has a greater impact than glucose
To understand this, it is first necessary to recognize that the amount of energy that the body stores directly in the form of glucose is actually quite limited. Specifically, a person weighing 70 kilograms has only about 4 grams of glucose circulating in their blood.
In contrast, our liver is capable of storing up to 100 grams of glycogen and up to 400 grams of glycogen in our muscles, which can be quickly converted to glucose for energy when needed.
Through other studies, Dr. Podra further found that muscle glycogen levels were more accurate predictors of fatigue than blood sugar levels. This finding suggests that glycogen, especially in muscle, may be a key factor in endurance exercise performance.
In a 2020 study on carbohydrate intake and recovery, Dr. Podla noted that glycogen stores are gradually depleted during prolonged exercise, such as a three-hour ride. It's important to note that this condition usually occurs before a sharp drop in blood sugar levels and athletes feel exhausted. This further underscores the importance of glycogen in maintaining athletic performance.
"If we could have a continuous glucose monitor that could measure muscle glycogen levels, it would be a huge help for athletes in training and competition. ”
The accuracy is not enough to serve the motion scene
The accuracy of the data provided by continuous glucose monitors in the exercise scenario has been controversial. Although these devices are able to show blood sugar fluctuations during sports such as cycling, people don't trust the data as much.
▲Continuous glucose monitors show how your blood sugar fluctuates during your ride, but can you trust the data?
In 2022, the International Journal of Exercise Physiology and Performance tested the accuracy of the data of several popular continuous glucose monitors on the market, and the test results showed that there were significant errors in the data of these continuous glucose monitors during exercise, especially after carbohydrate ingestion, which was further exacerbated.
Supersapiens' biosensors are "very unstable" under certain conditions, especially in cold environments, or when cycling, running, etc., without carrying a mobile phone, and their data accuracy is greatly reduced. Therefore, at the current state of technology, the data accuracy of continuous glucose monitors is not enough to fully meet the needs of sports scenarios.
The practical impact of real-time glucose monitoring
▲ Displaying glucose data on a bicycle computer in real time can cause the problem of information overload
While this may sound appealing in theory, in practice, athletes may find this information too complex to utilize effectively.
American gravel racer Lauren de Creshenzo shares her experience with it. "On the day of the race, I felt like it (the continuous glucose monitor) might not be as helpful as it was in the days leading up to the race," she mentioned. When I was doing glycogen storage, I found that it worked more obviously. "This further illustrates that for professional athletes, continuous glucose monitors may be more valuable during specific training phases or preparations, while during intense competitions, their impact may be relatively limited.
Strategies for Fueling Before a Ride: Quantity vs. Time
Researchers note that continuous glucose monitors can be a powerful tool that can help athletes more precisely understand their body's response to carbohydrates, so they can adjust their intake and timing to achieve optimal exercise.
In the case of De Creshenzo, the elite athlete who won competitions such as Unbound in 2021 shared his experience: "One of the big changes I made was to let the breakfast digest for two to three hours so that my blood sugar would stabilize before I started training. If you run out of the door after eating, you may feel exhausted for no apparent reason. Your blood sugar spikes when you eat breakfast and then goes all the way down because your body produces insulin to cope with this hyperglycemic state. If this hypoglycemic event occurs while cycling, you will suddenly lose energy, affecting your athletic performance. ”
She advises athletes to make sure their blood sugar has risen and stabilized at an appropriate level before starting cycling, so that they can provide better energy support for the rest of the exercise.
Continuous glucose monitors: a new tool to avoid exhaustion?
For endurance athletes, it is crucial to avoid exhaustion during long races. And continuous glucose monitors, as an emerging technological tool, are seen by some athletes as a "magic weapon" that may help them prevent burnout.
▲Eating at regular intervals may be more practical than continuous glucose monitoring
However, this technique is not flawless. McDermott noted that there is a certain delay in the transmission of data from continuous glucose monitors. This means that when an athlete is warned of hypoglycemia, they may have been in a state of declining blood sugar for some time.
Can monitoring blood sugar improve your sleep quality?
Will Jilin, a nutrition expert at EF Education-EasyPost, notes that tracking changes in blood sugar during sleep is undoubtedly one of the "outstanding applications" of continuous glucose monitoring technology.
▲A drop in blood sugar levels at night may indicate that your carbohydrate intake is low
He further elaborated that if your blood sugar drops to the threshold of low blood sugar in the middle of the night, it probably means that "you haven't been getting your carbohydrates up to the target throughout the day." This can make it difficult to maintain stable blood sugar levels during sleep, which can interfere with the quality of your sleep and prevent you from getting the rest and recovery you need. ”
Numbers vs. Intuition: The Double-edged Sword of Continuous Glucose Monitoring
In this age of data, our intuition and feelings seem to be gradually marginalized. However, for some situations, intuition may be much more important than we think.
▲The large and diverse amount of data provided by continuous glucose monitoring can be confusing for beginners
Continuous glucose monitoring is a technology that can have undesirable consequences if it falls into the hands of people who don't understand it well, and people can mistakenly see all blood sugar spikes as harmful signals. In fact, endurance athletes want to be able to eat enough carbohydrates before and after a workout to ensure a proper boost in blood sugar and provide the body with the necessary energy.
That excessive fear of elevated blood sugar can cause people to be too conservative in their actual dietary intake to meet their body's real needs.
What are the alternatives to continuous glucose monitoring?
Metabolic Efficiency Test: Accurately assess your energy needs
The best way to determine an individual's precise carbohydrate needs is to perform a metabolic efficiency test. Not only does this test provide in-depth insight into body function, but its accuracy and usefulness have been widely recognized.
It's worth noting that the sporting departments of some universities already offer this service, which costs around £110. During the test, participants wear a special mask and perform a hill climb test on a stationary bicycle. This setup allows researchers to precisely measure and analyze participants' energy expenditure and sources at different exercise intensities.
▲Gas exchange analysis shows exactly how long it takes for your body to move from using fat to carbohydrates as its primary energy source
McDermott further explained, "This test is able to tell you exactly how many grams of carbohydrates or fat your body is burning at any given exercise intensity, from 100 watts to 340 watts. "In contrast, metabolic efficiency tests provide more comprehensive and long-lasting information, helping individuals optimize their energy management and athletic performance over a longer period of time.
Blood lactate test: a training tool for elite athletes
In the footage and photographs of WorldTour training camps, we can often see coaches and medical teams busily collecting blood samples from riders' ears or fingertips. What they are doing is the blood lactate test, which has helped Norway achieve world-renowned results in areas such as middle-distance athletics and triathlon.
Lactic acid itself does not cause muscle fatigue (in fact, it can also be used as fuel by the body). However, the level of lactate in the blood is closely related to metabolic waste, and the accumulation of these metabolic wastes is the real cause of fatigue.
As a result, elite athletes are using the blood lactate test to accurately calculate their training area, which is often based on a three-zone model. Some sports scientists prefer to use this approach rather than the more popular Coggan model based on functional threshold power.
The advent of continuous lactate monitoring technology is expected to fill this gap, providing athletes and coaches with more comprehensive and real-time data support. However, it is a pity that this technology is still banned at the moment in UCI competitions.
Diverse applications of sensor technology
Continuous glucose monitors have become a data-logging tool for elite riders, giving them a key edge in the race. However, this is just one example of the many sensor applications.
▲One of the advanced technologies that today's athletes rely on in their pursuit of competitive advantage: the acquisition of real-time aerodynamic efficiency data is a direct manifestation of the progress of sensor technology
Now, there are several companies that claim that their aerodynamic sensors are capable of measuring CdA (aerodynamic drag coefficient) in real-time while the rider is traveling. This technology provides invaluable, immediate feedback to riders and teams, helping them optimize their riding position and gear selection to reduce drag and increase speed.
At the same time, some WorldTour teams are taking advantage of the FIC's license to use core temperature monitors during races. The sensors are able to monitor changes in the rider's body temperature in real time, providing the team with vital information about the rider's physical condition to make more informed tactical decisions.
In addition, we learned that professional teams are showing strong interest in hydration sensors that measure sweat rate. This sensor can help teams better understand how much water is lost during a race, ensuring they are hydrated in a timely manner to maintain optimal performance.
Continuous glucose monitoring: the transition from exercise to health
Although Supersapiens suffered a setback in the world of sports as a pioneer of continuous glucose monitoring technology, this does not mean that continuous glucose monitoring technology itself is coming to an end.
On the contrary, with the increasing emphasis on health management, the popularity of continuous glucose monitors in the health field is rising. This device provides a new option for non-diabetic patients to continuously monitor their blood glucose levels and could become their primary use case.
Continuous glucose monitoring technology still has a promising application in endurance exercise, but there are still some challenges to the technology, such as the need for further improvement in accuracy during exercise. At the same time, we also need to have a deeper understanding of the causes of blood sugar fluctuations at rest and their impact on athletic performance in endurance athletes.
One trend is already evident: the cyclists of the future will be recording more data than ever before. This change may be uncomfortable for the International Cycling Federation and traditional cycling purists, but it certainly represents a move towards a more scientific, data-driven movement of cycling.