[Oxidation of 13C-labeled glucose during loading of various intensity]

The purpose of the investigation was to assess the percentage utilization of administered glucose labelled with the natural isotope 13C during an intensive load on a bicycle ergometer (I) (1 hr, 75% VO2max) and a light load (L) (1.5 hr 45% VO2max). In the investigation participated four healthy volunteers who before pedalling drank 1.2 g.kg-1 labelled glucose dissolved in 400 ml water. The oxidation of administered glucose was measured in expired 13CO2. In the course of load I 15% were oxidized and during load L 47% of the administered 13C glucose. The difference in utilization of administered glucose during I and L loads is significant (p less than 0.025). The blood sugar level rose significantly during load I, insulinaemia during load I as well as L, but in load I it was significantly lower as compared with load L (p less than 0.05). This investigation supplements findings on the lower utilization of concentrated glucose solutions during intensive physical loads.