n South African Journal of Sports Medicine - Maintenance of hyperglycaemia does not improve performance in a 100 km cycling time trial : original research article




The aim of this study was to determine whether the elevated plasma glucose oxidation rate (~ 1.8 g.min-1) in the latter stages of prolonged exercise in subjects in which hyperglycaemia ( 10 mmol.l-1) is maintained via a glucose clamp, improves 100 km cycling time-trial (TT) performance.

Seven endurance-trained male cyclists (224 yrs) participated in this randomised crossover trial. On two occasions, separated by 7 - 10 days, subjects performed a self-paced TT in the laboratory. During one TT blood glucose was maintained at a euglycaemic concentration of 5 mmol.l-1 (ETT) and during the other, at 10 mmol.l-1 (HTT). Each TT was interspersed with 5 X 1 km high-intensity periods (HIP) and 4 X 4 km HIP, in an attempt to mimic the variable intensity of competitive road races. Subjects were instructed to complete the TT in the 'fastest time possible', taking the 9 HIP (21 km) into consideration.
There were no significant differences between ETT and HTT in overall time (143:097:14 v. 142:237:16 min:s), mean power (27539 v. 27939 W) and heart rate (1609 v. 15811 beats.min-1).
Time trial performance over 100 km is not improved by maintaining a hyperglycaemic (10 mmol.l-1) blood glucose concentration.


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