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n South African Journal of Sports Medicine - Maintenance of hyperglycaemia does not improve performance in a 100 km cycling time trial : original research article
Objectives. 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.
Design. Seven endurance-trained male cyclists (22+4 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.
Results. There were no significant differences between ETT and HTT in overall time (143:09+7:14 v. 142:23+7:16 min:s), mean power (275+39 v. 279+39 W) and heart rate (160+9 v. 158+11 beats.min-1).
Conclusion. Time trial performance over 100 km is not improved by maintaining a hyperglycaemic (10 mmol.l-1) blood glucose concentration.
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