Prevalence of hypoglycemia following pre-exercise carbohydrate ingestion is not accompanied By higher insulin sensitivity.
Level 4 - case-series / case-control
Non-randomized comparative study stratified post hoc by physiological response
PubMed 12500984 · doi:10.1123/ijsnem.12.4.398
What was done
Twenty trained athletes (mean VO2max 61.8 +/- 1.4 ml.kg-1.min-1) consumed 500 ml of a beverage containing 75 g of glucose 45 minutes before cycling exercise (20 minutes of submaximal exercise at 74 +/- 1% VO2max followed immediately by a time trial). Subjects were assigned to a Hypo group (<3.5 mmol/L) or Non-hypo group (>=3.5 mmol/L) based on their plasma glucose nadir during submaximal exercise. An oral glucose tolerance test was conducted to calculate an index of insulin sensitivity (ISI).
What was found
Ten athletes were classified into the Hypo group and 10 into the Non-hypo group. The submaximal exercise plasma glucose nadir was significantly lower in the Hypo group compared with the Non-hypo group (2.7 +/- 0.1 vs. 4.1 +/- 0.2 mmol/L, p < .01). No significant difference was detected in ISI between the Hypo and Non-hypo groups (3.7 +/- 0.4 vs. 3.8 +/- 0.5, respectively).
Why it matters
This suggests that individual susceptibility to rebound hypoglycemia following pre-exercise glucose ingestion is not driven by higher peripheral insulin sensitivity.
Limits
The sample size was small (n = 20 total, 10 per group). Only trained athletes were evaluated, and insulin sensitivity was estimated via an oral glucose tolerance test rather than a hyperinsulinemic-euglycemic clamp. Performance metrics from the time trial were not reported in the abstract.
Cited by
- supports Consuming rapidly digestible carbohydrates immediately before starting exercise can induce a transient dip in blood glucose because insulin release and exercise-induced muscle glucose uptake simultaneously lower circulating glucose levels.