Everyone with insulin-dependent diabetes wants to know as reliably and easily as possible the course of glucose levels during exercise. Several CGM sensors are on the market, recently the Free Style Libre Flash Monitor (FLM) has been introduced.

Objective: what is the effect of use during extreme exercise on the accuracy of both the CGM and the FLM.

Methods: Both CGM (Medtronic) and FLM (Abbott) were compared to the finger prick/strip (cBGMstrip) during a Bas van de Goor Foundation mountainbike challenge in the Mont-Blanc massif (218km, 7900hm).

Results: CGM and FLM are clearly less accurate during a period of intensive efforts compared to normal daily activities. In addition, glucose values in the interstitial fluid frequently were higher than found with capillary measurements, also in the lower glucose concentrations. This makes the signaling of hypoglycemia through CGM use less reliable during extreme exercise. Clinically relevant differences were also seen when comparing CGM and FLM (see Table).

Conclusions: During extreme exercise, CGM and FLM often showed higher interstitial glucose concentrations than actually present, also at the hypoglycemic range. This is in contrast to measurements taken under normal conditions. In addition, results of the continuous measurement technics differed considerably. This makes the use of CGM and FLM less reliable during extreme exercise.


E. Delgado: Advisory Panel; Self; Abbott, Almirall, S.A., AstraZeneca, Esteve, Novo Nordisk A/S, Sanofi. Research Support; Self; AstraZeneca, Menarini Group. Speaker's Bureau; Self; Boehringer Ingelheim International GmbH, Lilly Diabetes. M.M. Fokkert: None. P. van Dijk: None. M.A. Edens: None. A. Diez: None. R.J. Slingerland: None. H. Bilo: None.

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