Continuous Glucose Monitoring (CGM) in Endurance Athletes
Interpretation & relevance
Key Findings
CGM records interstitial glucose in real time, which is assumed to be equivalent to blood glucose
No current consensus on how to interpret CGM measurements in athletes with normal glucose control; well-defined approaches to using it to improve performance and health are lacking
In several studies, blood glucose regulation in endurance athletes differs from that in healthy controls
Endurance athletes regularly perform demanding sessions and can be exposed to high or low energy and/or carbohydrate availability, which affects glucose levels and regulation
Full text, checked 2026-09-27: the review discusses sensor lag (interstitial glucose trails blood by up to 15 min after carbohydrate intake) and lower CGM precision during exercise; that demanding sessions can reduce glucose tolerance acutely and the next day (the same authors' Flockhart 2021, Cell Metabolism, is cited for glucoregulation under high training loads); and CGM in an ultramarathon (Ishihara 2020), where normoglycemia held regardless of carbohydrate intake
Practical Application
Current-opinion review: CGM gives real-time interstitial glucose assumed to track blood glucose, but there is no consensus on interpreting it in athletes with normal glucose control and no defined way to use it to improve performance or health; athletes' glucose regulation differs from healthy controls and shifts with energy/carbohydrate availability. For a masters athlete CGM is an experimental tool, not a guide to action
Not from this paper; the base's own practice: do not chase a "flat" glycemic curve — an athlete's physiology differs from a metabolic patient's, and a low reading during a long session is a fuelling cue, not a disease marker
Full text, checked 2026-09-27: possible uses the review discusses — monitoring glucose variability, energy availability and recovery status, and post-exercise glucose as a possible early sign of overtraining; using CGM to decide acute carbohydrate intake has substantial limits: interstitial glucose lags blood by up to 15 min after carbohydrate, precision is lower during exercise, and sensor site shifts readings
Limitations
Current opinion, not a systematic review/meta-analysis; no data in the abstract
One author (Larsen) is a co-founder of a company using CGM data (declared conflict of interest — full text, checked 2026-09-27)
A fast-moving field; protocols may emerge
How this entry was checked and changed
Why this level
regraded 2026-09-27 from B: current-opinion narrative review without systematic method; the abstract carries no data
Content correction 2026-09-27
Level B -> C+ per KB-LEVEL-RUBRIC (current-opinion review without systematic method).
Lead bullet now carries the review's own position (no consensus, no defined approach, athletes differ from controls, availability shifts glucose); the Flockhart 2021 / Ishihara 2020 / sensor-lag claims labelled as full-text content; "do not chase a flat curve" labelled as the base's own practice.
Cross-reference "REF-528 ultra (CGM for individual CHO needs)" -> REF-528 does not mention CGM; relabelled as the ultra nutrition position stand.
Lines labelled "full text; not checked" were read against the open-access full text (PMC10933193): 1 confirmed and relabelled; 2 corrected to what the paper says.