Paper Information

Journal:   OLYMPIC   FALL-WINTER 2003-2004 , Volume 11 , Number 3-4 (SERIAL 24); Page(s) 51 To 66.
 
Paper: 

THE EFFECT OF GLUCOSE AND INSULIN ON ENERGY EXPENDITURE AND SUBSTRATE OXIDATION DURING PROLONGED INTENSE EXERCISE

 
 
Author(s):  MOHEBI HAMID*
 
* FACULTY OF PHYSICAL EDUCATION AND SPORT SCIENCES. UNIVERSITY OF GUILAN
 
Abstract: 
In the present study the effects of glucose and insulin infusion throughout a prolonged intense exercise on energy expenditure and substrate metabolism were examined. Eight male cyclists performed ergometer with 70% intensity for 120 min on two separate occasions under either an intravenus glucose clamp(G)at10 mmol/l,or a glocose(10mmol/1) and insulin clamp (GI) at 40 mU/segm/ min.Fasting venous blood samples were taken at rest both pre and post clamp and during exercise were analyzed for glucose, insulin and NEFA concentrations Expired air also, was collected for detemination O__24 uptake and CO__2 production over each minute to calculate energy expenditure and substrate oxidation Blood glucose concentration increased significantly and was maintained at 10 mmol/I in both trials The prime infusion of insulin caused plasma insulin concentrations to rise significantly (P<0.001). Plasma insulin were significantly higher during exercise in the GI trial compared with the Gtrial (p<0.05). Plasma NF-FA concentrations decreased between 67% and 76% from rest to the end of the exercise (P<0.01). Energy expenditure rise significantly during exercise in both trials, but infusion of insulin made no difference to energy expenditure during exercise The relative contribution of CHO to energy expenditure increased significantly up to 15 min of exercise (p<0.001) and thereafter increased gradually in the 70% GI trial up to 120 min (p<0.05). Insulin infusion made no significant difference to substrate oxidation (CHO, fat and protein metabolism). The results of this study confirm that low concentrations of NEFA, together with high plasma glucose and insulin concentrations respresents a condition that facilitates a rate of glucose utilization by active muscle and increases the contribution of CHO to energy expenditure. However, we conclude that glucose and insulin and intense exercise act synergistically to enhance energy expenditure and to maintain CHO oxidation throughout the exercise.
 
Keyword(s): EXEREISE: GLUCOSE : INSULIN, CARBOHYDRATE OXIDATION: FAT OXIDATION ENERGY EXPENDITURE : GLUCOSE CLAMP TECHNIQUE
 
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