Accuracy of Continuous Glucose Monitoring (CGM) during Continuous and High-Intensity Interval Exercise in Patients with Type 1 Diabetes Mellitus

Abstract

Continuous exercise (CON) and high-intensity interval exercise (HIIE) can be safely performed with type 1 diabetes mellitus (T1DM). Additionally, continuous glucose monitoring (CGM) systems may serve as a tool to reduce the risk of exercise-induced hypoglycemia. It is unclear if CGM is accurate during CON and HIIE at different mean workloads. Seven T1DM patients performed CON and HIIE at 5% below (L) and above (M) the first lactate turn point (LTP1), and 5% below the second lactate turn point (LTP2) (H) on a cycle ergometer. Glucose was measured via CGM and in capillary blood (BG). Differences were found in comparison of CGM vs. BG in three out of the six tests (p < 0.05). In CON, bias and levels of agreement for L, M, and H were found at: 0.85 (−3.44, 5.15) mmol·L−1, −0.45 (−3.95, 3.05) mmol·L−1, −0.31 (−8.83, 8.20) mmol·L−1 and at 1.17 (−2.06, 4.40) mmol·L−1, 0.11 (−5.79, 6.01) mmol·L−1, 1.48 (−2.60, 5.57) mmol·L−1 in HIIE for the same intensities. Clinically-acceptable results (except for CON H) were found. CGM estimated BG to be clinically acceptable, except for CON H. Additionally, using CGM may increase avoidance of exercise-induced hypoglycemia, but usual BG control should be performed during intense exercise.

Impact of physical exercise on sensor performance of the FreeStyle Libre intermittently viewed continuous glucose monitoring system in people with Type 1 diabetes: a randomized crossover trial

“…Although previous research found that the iCGM system was accurate in real-life conditions and may improve glycaemic control [1,2,5,15], during exercise the accuracy of absolute glucose values measured is only moderate and additional finger-prick glucose measurements are required. In comparison to a previous study performing exercise with a similar mean exercise intensity using the Medtronic Enlite TM sensor (Medtronic Diabetes, Northridge, CA, USA) the mean absolute relative difference was found to be 12.8% [16]. However, trend arrows of iCGM providing information about velocity of glucose changes could still be of value during exercise.…”

Performance of the Freestyle Libre flash glucose monitoring (flash GM) system in individuals with type 1 diabetes: A secondary outcome analysis of a randomized crossover trial

“…One might assume that physical exercise per se did not deteriorate the performance of the flash GM system, because the rate of change in glucose appeared to result in inaccuracy. In the present study, the MARD during exercise was inherently higher than that with other CGM devices such as Minimed 640G (Medtronic), Dexcom G4 Platinum (Dexcom) or Paradigm Veo Enlite (Medtronic) (mean absolute relative difference/MARD, ~18%) . A systematic overestimation of 2.7 mmol/L might suggest that anticipation of intervention to avoid exercise‐induced hypoglycaemia is required as soon as an interstitial glucose level of 7.2 mmol/L is reached.…”

Continuous Glucose Monitoring and Exercise in Type 1 Diabetes: Past, Present and Future

“…While CGM provides a cost effective [ 36 ] way to continuously monitor interstitial glucose levels of patients in a practical or research setting [ 37 ], its accuracy during various forms of exercise has occasionally been questioned, and is thus still under investigation [ 38 , 39 , 40 , 41 , 42 ]. With improvements in sensor technology and device-related algorithms, CGM systems have rapidly improved their accuracy over the past decade.…”

“…With improvements in sensor technology and device-related algorithms, CGM systems have rapidly improved their accuracy over the past decade. During that time, studies have assessed CGM accuracy during continuous aerobic [ 39 , 40 , 41 , 42 ], high intensity interval [ 39 , 40 ], and resistance exercise [ 42 ].…”

“…Another study, published in 2016 [ 40 ], compared the accuracy of the Medtronic Guardian Real-Time system using Enlite sensors (Medtronic Diabetes, Northridge, CA, USA) during three different aerobic activity and HIIE levels. Continuous glucose monitoring was shown to overestimate capillary glucose values during low, moderate, and higher intensity aerobic exercise (5% below and above the first lactate turn point and 5% below the second lactate turn point), and for three separate HIIE protocols (20 s maximal sprints every 120, 60, or 20 s for a total of 30 min, with the intensity between intervals being identical to each of the three aerobic exercise protocols) performed by individuals with T1D.…”