Effect of a 2-h hyperglycemic-hyperinsulinemic glucose clamp to promote glucose storage on endurance exercise performance |
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Authors: | Maclaren D P M Mohebbi H Nirmalan M Keegan M A Best C T Perera D Harvie M N Campbell I T |
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Institution: | (1) Research Institute for Sport & Exercise Sciences, Liverpool John Moores University, Henry Cotton Campus, Webster Street, Liverpool, L3 2ET, UK;(2) Department of Anaesthesia, Wythenshawe Hospital, Manchester, UK |
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Abstract: | Carbohydrate stores within muscle are considered essential as a fuel for prolonged endurance exercise, and regimes for enhancing
such stores have proved successful in aiding performance. This study explored the effects of a hyperglycaemic–hyperinsulinemic
clamp performed 18 h previously on subsequent prolonged endurance performance in cycling. Seven male subjects, accustomed
to prolonged endurance cycling, performed 90 min of cycling at ~65% VO2max followed by a 16-km time trial 18 h after a 2-h hyperglycemic–hyperinsulinemic clamp (HCC). Hyperglycemia (10 mM) with insulin
infused at 300 mU/m2/min over a 2-h period resulted in a total glucose uptake of 275 g (assessed by the area under the curve) of which glucose
storage accounted for about 73% (i.e. 198 g). Patterns of substrate oxidation during 90-min exercise at 65% VO2max were not altered by HCC. Blood glucose and plasma insulin concentrations were higher during exercise after HCC compared with
control (p < 0.05) while plasma NEFA was similar. Exercise performance was improved by 49 s and power output was 10–11% higher during
the time trial (p < 0.05) after HCC. These data suggest that carbohydrate loading 18 h previously by means of a 2-h HCC improves cycling performance
by 3.3% without any change in pattern of substrate oxidation. |
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