How Can Continuous Glucose Monitoring Aid in Fuel Strategy for Long-Cycling Events?

April 15, 2024

In the highly competitive world of endurance sports, athletes are constantly seeking ways to optimise their performance. One such approach gaining popularity is the use of Continuous Glucose Monitoring (CGM) systems to manage fuel strategies during long-cycling events. In this comprehensive guide, we will delve into the relationship between blood glucose levels and athletic performance, the role of carbohydrates as an energy source during high-intensity exercise, and how CGM systems can provide crucial real-time data to athletes.

Understanding Glucose’s Role in Athletic Performance

Before delving into the specifics of CGM, it’s crucial to understand the role glucose plays in the body, particularly during intense physical activity. As the main source of energy, glucose is instrumental in fuelling an athlete’s performance during a race.

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During exercise, your muscles need a reliable source of energy. This energy primarily comes from glucose, a type of sugar, which is stored in the muscles and liver as glycogen. When you start exercising, your body begins to break down these glycogen stores into glucose, providing the fuel needed to support your activity.

However, the body’s glycogen stores are limited, and when they deplete, it can lead to fatigue, a phenomenon known in the athletic community as "bonking" or "hitting the wall". In long-cycling events, maintaining optimal blood glucose levels becomes critical to prevent bonking and sustain high levels of performance.

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Carbohydrates: The Key Source of Glucose

A diet rich in carbohydrates is essential for athletes, especially those engaged in endurance sports. Carbohydrates are the body’s preferred source of glucose, and thus, a key ingredient in an athlete’s nutrition plan.

When you consume carbohydrates, your body breaks them down into glucose, which is then either used immediately for energy or stored in the muscles and liver as glycogen. The type and timing of carbohydrate intake can significantly influence blood glucose levels and consequently, athletic performance.

For instance, consuming high-glycemic index carbohydrates before an event can cause a rapid spike in blood glucose levels, providing immediate energy. However, this spike is often followed by a drastic drop, which can negatively impact performance. On the other hand, consuming low-glycemic index carbohydrates provides a more steady release of glucose into the bloodstream, maintaining energy levels over a longer time.

The Value of Continuous Glucose Monitoring (CGM) for Athletes

High performance during long-cycling events relies heavily on the ability to maintain optimal glucose levels. This is where Continuous Glucose Monitoring (CGM) comes in.

CGM systems are devices that measure glucose levels in real-time, throughout the day and night. Initially developed for individuals with diabetes, these systems have found their way into the realm of sports due to their potential to provide vital data on an athlete’s glucose levels before, during, and after exercise.

Having access to this continuous stream of data allows athletes and their coaches to understand how their bodies respond to different intensities of exercise, types of fuel (carbohydrate sources), and timing of fuel intake. This information can help refine an athlete’s nutrition and fuel strategy, ensuring they maintain optimal blood glucose levels, thereby enhancing performance and recovery.

Applying CGM Data to Fuel Strategy

Using the data provided by CGMs, athletes can develop a more personalised fuel strategy. By understanding how their blood glucose levels respond to different variables, they can adapt their diet and fuel intake to ensure they maintain the right glucose balance during a race.

For example, an athlete may notice that their blood glucose levels drop significantly after an hour of intense cycling. To prevent this drop, they could plan to consume a high-glycemic index carbohydrate source, like a sports gel, at the 45-minute mark to maintain their glucose levels.

Additionally, CGM data can also inform post-race recovery strategies. By monitoring glucose levels after a race, athletes can observe how their bodies recover and adjust their intake of carbohydrates and protein to replenish glycogen stores and support muscle repair.


While CGM technology cannot replace sound training and nutrition practices, it offers an innovative way to fine-tune fuel strategies for long-cycling events. In the race to the top, access to real-time glucose data could make all the difference between maintaining energy levels throughout the race or hitting the dreaded wall. It’s an exciting time in the world of sports nutrition and performance enhancement, and we eagerly await more research and data in this field.

Please note that while CGM systems offer valuable insights, athletes should consult with a healthcare professional or a sports nutritionist before making any significant changes to their diet or training regimen based on CGM data.

Lastly, remember that CGMs are tools to aid performance, but they do not replace the need for proper training, a balanced diet, and adequate rest. In sports as in life, balance is key, and understanding and respecting our bodies’ needs is the first step toward achieving our goals.

Interpreting CGM Data: A Game-Changer for Endurance Athletes

With the advent of CGM systems, endurance athletes are empowered with a tool that can provide real-time data, allowing them to make informed decisions about their fuel strategies. However, understanding how to interpret and apply this data is crucial to optimising its benefits.

The primary objective of using a CGM system is to track the fluctuations in blood glucose levels. These fluctuations can be influenced by several factors including carbohydrate intake, intensity of exercise, stress and sleep patterns. A CGM provides data about these variances in a graph, with glucose values plotted over time.

For instance, a sudden rise in glucose levels could indicate a high intake of carbohydrates or an intense training session. Conversely, a sharp drop may suggest low energy availability or an insufficient intake of carbohydrates. Understanding these patterns can enable athletes to modify their diet or training plans accordingly.

Moreover, CGM systems can reveal glucose variability, that is, the degree of fluctuation in blood glucose levels. High variability can increase the risk of “bonking”, while a lower variability suggests stable energy levels. Hence, by using CGMs, athletes can aim to maintain stable glucose levels, supporting sustained energy availability.

Real-time tracking also highlights post-exercise recovery periods. Athletes can observe how quickly their glucose levels return to normal post-race, which can provide insights into their recovery rate and inform their post-race nutrition strategy.

However, interpreting CGM data requires a firm understanding of these aspects. Consulting with a healthcare professional or a sports nutritionist can guide athletes in making the most of these insights and ensuring they’re making safe, informed decisions about their fuel strategies.

The Future of CGM in Sports: A Continuous Learning Curve

The arena of sports nutrition and performance enhancement is constantly evolving, with innovative technologies like CGM systems catapulting athletes into a new era of personalised fuel strategies. However, as with any technology, its true potential can only be realised when coupled with a comprehensive understanding of its application and interpretation.

There’s an increasing interest in this field, with a growing number of studies exploring the role of CGM in enhancing athletic performance. A quick search on Google Scholar or PubMed will yield free articles and PMC free papers discussing the latest research on this topic.

Continuous glucose monitoring has also been a focal point in high-intensity sports and endurance events. Observing interstitial glucose levels in real time can be a game-changer for athletes who can adjust their carbohydrate intake and mitigate the risk of blood sugar crashes during long races.

However, the use of CGM is not without its challenges. Accurately interpreting the data and understanding the implications for diet and training regimes is complex. For that reason, athletes are urged to consult with healthcare professionals or sports dietitians to ensure they’re making safe and informed decisions.


The advent of CGM technology has opened up exciting possibilities for endurance athletes. The ability to monitor blood glucose levels in real time provides an unprecedented level of insight into an athlete’s energy availability and recovery rate.

However, while CGM systems offer a valuable tool, they’re not a standalone solution. Athletes must remember that maintaining a balanced diet, following a structured training plan, and ensuring adequate rest are all critical components of peak performance.

As research continues to shed light on the benefits and applications of CGM in sports, athletes and coaches will be better equipped to integrate this technology into their strategies effectively. But as with any tool, it’s important to use it wisely and responsibly. Always consult with a healthcare professional or sports dietitian before making any significant changes to your diet or training regimen based on CGM data.

In the race to the top, remember that understanding and respecting your body’s needs is the first step towards achieving your goals.