The Use of Continuous Glucose Monitors in Sport: Possible Applications and Considerations

Abstract

This review discusses the potential value of tracking interstitial glucose with continuous glucose monitors (CGMs) in athletes, highlighting possible applications and important considerations in the collection and interpretation of interstitial glucose data. CGMs are sensors that provide real time, longitudinal tracking of interstitial glucose with a range of commercial monitors currently available. Recent advancements in CGM technology have led to the development of athlete-specific devices targeting glucose monitoring in sport. Although largely untested, the capacity of CGMs to capture the duration, magnitude, and frequency of interstitial glucose fluctuations every 1–15 min may present a unique opportunity to monitor fueling adequacy around competitive events and training sessions, with applications for applied research and sports nutrition practice. Indeed, manufacturers of athlete-specific devices market these products as a “fueling gauge,” enabling athletes to “push their limits longer and get bigger gains.” However, as glucose homeostasis is a complex phenomenon, extensive research is required to ascertain whether systemic glucose availability (estimated by CGM-derived interstitial glucose) has any meaning in relation to the intended purposes in sport. Whether CGMs will provide reliable and accurate information and enhance sports nutrition knowledge and practice is currently untested. Caveats around the use of CGMs include technical issues (dislodging of sensors during periods of surveillance, loss of data due to synchronization issues), practical issues (potential bans on their use in some sporting scenarios, expense), and challenges to the underpinning principles of data interpretation, which highlight the role of sports nutrition professionals to provide context and interpretation.

Continuous Glucose Monitoring in Endurance Athletes: Interpretation and Relevance of Measurements for Improving Performance and Health

“…Also, female endurance athletes with secondary functional hypothalamic amenorrhea, which can be a consequence of low energy availability, have been found to exhibit lower capillary glucose levels during fasting and submaximal exercise than eumenorrheic subjects [ 54 ]. These, and other studies previously discussed by Bowler and colleagues [ 55 ] suggest that glucose measurements can be used as a marker of reduced energy availability.…”

Continuous Glucose Monitoring (CGM) in Sports—A Comparison between a CGM Device and Lab-Based Glucose Analyser under Resting and Exercising Conditions in Athletes

“…As also healthy people are advised to avoid hypoglycemia during exercise in order to delay fatigue, the occurrence of a lag time probably evokes a delayed reaction and experiencing hypoglycemia. Despite the increasing interest and application in athletes, data on healthy, active subjects are missing [7]. The authors hypothesise that there will be a difference between CB and ISF in healthy subjects, just as previously seen in people with diabetes and due to the physiological shift between ISF and CB glucose.…”

“…Therefore, regular carbohydrate (CHO) intake during exercise, which should be adapted to the overall duration of the exercise, is recommended [4][5][6]. While free blood glucose concentration is no proper indicator of CHO availability, maintaining adequate blood glucose levels during exercise is assumed to reflect a successful CHO intake strategy during exercise [7]. Sensor-based continuous glucose monitoring (CGM) is a minimally invasive technology that allows for the recognition of glucose flux and is known as a therapeutic application for individuals managing diabetes.…”

Methodology for studying Relative Energy Deficiency in Sport (REDs): a narrative review by a subgroup of the International Olympic Committee (IOC) consensus on REDs

“…Best practice procedures, including overnight fasting to assess glucose and lipid metabolism from blood samples, are outlined earlier (see Blood Work: best practice principles ). Although continuous glucose monitoring (CGM) was developed decades ago for the management of diabetes, more recently, it has emerged as an assessment tool in sport,93 with the hypothesis that alterations in continuous or overnight glucose values in situations of LEA might be assessed via CGM for diagnostic purposes. Until research is undertaken to confirm the value of CGM use for the assessment of impaired glucose metabolism associated with LEA, caveats around the expense and interpretation of data from these devices should be considered 93…”