In the last couple of years, continuous glucose monitors (CGM) have become a new commercial technology for endurance athletes to use. The underlying performance function of a CGM is to observe and monitor blood glucose levels, and to detect trends and patterns that give a more complete picture of how different foods, sport fuels, exercise intensity can affect performance. 

The CGM device measures the amount of glucose in the interstitial fluid (a thin layer of fluid surrounding the cells tissue below your skin) inside your body. A sensor is generally placed on the back of the arm or belly, and most CGM devices take readings every one of five minutes, all day and night. An adhesive tape holds the waterproof sensor in place for up to 7-14 days. CGM systems have a transmitter or sensor that wirelessly sends glucose data from the sensor to a device, such as a smartphone, to show the data. In general, CGM devices are used for people who have medical conditions and need to monitor their blood levels regularly. 

Comparatively, glucometers are blood monitoring devices that also help measure sugar or glucose levels by analyzing small amounts of blood, usually from a finger tip. A lancet lightly pricks the surface of the skin to obtain the blood, and the meters show the current blood sugar level.

Pros and Cons CGM Devices



  • No fingersticks and need to draw blood for samples
  • Blood glucose readings are more accurate at the same point in time compared to CGM devices. We observed the readings delayed between 10-20 minutes
  • Samples are uploaded automatically to a smart device
  • CGM sensors are expensive. Generally devices costs between $75-100 CAD for 14 days of use 
  • Supporting app technology can better help identify trends and patterns with impacts of food, exercise, sleep and more. 
  • Steep learning curve. Research is still at its beginning stages of how athletes can use CGM devices to learn how they can better perform. 
  • Customer service with companies is fantastic. If a device is not functioning, companies will generally replace sensors immediately, and will send through priority shipping. 
  • There is limited research on the impacts of psychological reactions with CGM devices, however, the small sample size of the SPN community who used the devices reported anxiousness in the first week, because they didn’t quite understand how best to interpret the data, and were also concerned they had glucose issues. (It should be noted, all of the users were fine and enjoyed experimenting with the devices)


Over the course of 3 years, we tested a variety of glucose meters and here is our quick review of them. 

Dexcom 5 and 6



  • Accessible to purchase, fast delivery and customer service was great
  • The units are expensive
  • Replacing faulty sensors was quick and easy
  • There is a lot of material that is disposed of after usage.
  • Calibrating the sensor helped provide a more accurate representation of glucose levels
  • Dexcom 5 and 6 transmitter battery life lasts for 10 days, compared to Abbot Libre sensors (14 days)
  • The calibrating option ‘felt’ it provided more of an accurate measure than the Abbot Libre devices
  • A supportive adhesive is a MUST around the transmitter. The general adhesive does not hold adequate to the surface of the skin.

Abbot Libre Freestyle 1, 2 and Biosensor (Technology SuperSapiens uses)



  • Accessible to purchase, fast delivery and customer service was great
  • The units are expensive ranging from $75-100
  • Replacing faulty sensors was quick and easy with the Abbot Canada

  • None of the 8 Biosensor with SuperSapiens were faulty, so we couldn’t determine the level of customer service.
  • No Calibration function


  • The glucometer and CGM measures were never the same. There was regularly a 1-2 mmol/L difference between the two measures. Although the trends were similar. 

  • All sensors last 14 days compared to Dexcom sensors at 10 days
  • Sensor adhesive holds firm to the skin. So long as the sensor didn’t bump against something, it remained intact. 

Main observations from using the CGM Devices

  • A glucometer provides a more clear point in time measure than the CGM, when measuring blood glucose
  • CGM is often delayed, which doesn’t really help to avoid bonking. Often times we bonked first then the CGM would inform us 20 minutes later that we bonked 
  • CGM is fun and informative toward detecting trends and patterns that give a more complete picture of how different foods, stress, sport fuels, exercise intensity can affect glucose levels and performance 
  • CGMs maybe more promising for long steady efforts, such as weekend endurance training and long course Triathlon racing, where athletes generally hold a steady tempo and can modify their nutrition strategy on the go. Comparatively, for bike racing, where intensity is high and random, the sensor is less functional, because there is a 20 minute delay in glucose readings. 

What we liked about using CGM devices

Overall the CGM devices are a fun experience that shouldn’t be taken too seriously. Glucose measurement is one data point of many that could affect performance. Using a CGM device for performance helps validate what you already know, and provides an opportunity to test new things to see how energy levels are affected. Our biggest take away from using the device was validating UCAN SuperStarch®, a slow release carbohydrate compared to other fast-acting sport fuels. To learn more about our small study, click here.



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