Pre-Exercise Ingestion of Carbohydrate and Transient Hypoglycemia During Exercise

Abstract

To study the occurrence and contributing factors of transient hypoglycemia after pre-exercise ingestion of glucose after a 4-hour fast, 19 well-trained cyclists ingested 50 grams of glucose dissolved in water around noon after having a normal breakfast. The ingestion of the glucose solution was followed by 30 minutes rest after which the subjects cycled for 40 minutes at 60% of the predetermined maximal power output. Every 10 minutes blood was sampled for determination of glucose, catecholamines, and insulin concentrations. In 6 subjects (hypo-group) plasma glucose levels dropped transiently below 3.0 mmol/l, while in the other 13 subjects (non-hypo group) plasma glucose level remained above this level. Although at the onset of exercise the plasma glucose levels were lower in the hypo-group, insulin levels were similar in both groups, suggesting a higher insulin sensitivity in the hypo-group. During exercise, norepinephrine was lower in the hypo-group, indicating a lower sympathetic activity in the hypo-group. The lowest plasma glucose levels in both groups were observed after 20 minutes of exercise, after which plasma glucose concentration returned to normal levels. It is concluded that pre-exercise carbohydrate ingestion after a 4-hour fast is sufficient to induce a transient hypoglycemia. The data suggest that the occurrence of hypoglycemia is determined by a combination of a high insulin sensitivity, a small amount of ingested glucose, and a low sympathetic activity.

The Effect of Pre-Exercise Galactose and Glucose Ingestion on High-Intensity Endurance Cycling

“…This adds to the evidence that rebound hypoglycaemia occurs, but not all individuals appear to be susceptible (23,29). Individual responses appear very relevant.…”

“…The pre-exercise ingestion of glucose in comparison to placebo has been shown to have both negative (15,28) and positive (40,41) effects on endurance performance, as well as providing no additional benefit (3,24,43). Some of these findings may be reconciled since glucose ingestion can be associated with the occurrence of rebound hypoglycaemia during subsequent exercise (23,29), which may limit the ability to enhance endurance performance.…”

“…There is evidence that not all individuals appear to be susceptible to rebound hypoglycaemia (23,29) and some are even able to maintain endurance performance despite transient hypoglycaemic episodes (14). However, previous studies have variably defined hypoglycaemia, with thresholds of <2.5 mmol.l -1 (14,39), ≤3.0 mmol.l -1 (29,33) and ≤3.5 mmol.l -1 (15,23), making interpretation of susceptibility difficult.…”

“…However, previous studies have variably defined hypoglycaemia, with thresholds of <2.5 mmol.l -1 (14,39), ≤3.0 mmol.l -1 (29,33) and ≤3.5 mmol.l -1 (15,23), making interpretation of susceptibility difficult. Defining rebound hypoglycaemia as a plasma glucose concentration 3.0 mmol.l -1 is most appropriate in a continuous cycling context as it is consistent with definitions of symptomatic hypoglycaemia (12,33).…”

Pengaruh penerapan carbohydrate loading modifikasi terhadap kesegaran jasmani atlet sepak bola

“…Salah satu akibat dari suatu aktivitas fisik atau olahraga adalah penurunan glukosa darah adapun besarnya penurunan tergantung pada intensitas dan lama aktivitas. 20 Pada beberapa kondisi penurunan glukosa darah dapat mencapai hingga pada tahap hipoglikemia, hal tersebut merepresentasikan simpanan glukosa dan glikogen yang makin berkurang. 20 Terdapat perbaikan pada hasil pengukuran glukosa darah.…”