Glucose uptake is increased in trained vs. untrained muscle during heavy exercise

TY - JOUR

T1 - Glucose uptake is increased in trained vs. untrained muscle during heavy exercise

AU - Kristiansen, Søren

AU - Gade, Jon

AU - Wojtaszewski, Jørgen

AU - Kiens, Bente

AU - Richter, Erik

N1 - 2000 5200 107

PY - 2000

Y1 - 2000

N2 - Endurance training increases muscle content of glucose transporter proteins (GLUT-4) but decreases glucose utilization during exercise at a given absolute submaximal intensity. We hypothesized that glucose uptake might be higher in trained vs. untrained muscle during heavy exercise in the glycogen-depleted state. Eight untrained subjects endurance trained one thigh for 3 wk using a knee-extensor ergometer. The subjects then performed two-legged glycogen-depleting exercise and consumed a carbohydrate-free meal thereafter to keep muscle glycogen concentration low. The next morning, subjects performed dynamic knee extensions with both thighs simultaneously at 60, 80, and until exhaustion at 100% of each thigh's peak workload. Glucose uptake was similar in both thighs during exercise at 60% of thigh peak workload. At the end of 80 and at 100% of peak workload, glucose uptake was on average 33 and 22% higher, respectively, in trained compared with untrained muscle (P < 0.05). Training increased the muscle content of GLUT-4 by 66% (P < 0. 05). At exhaustion, glucose extraction correlated significantly (r = 0.61) with total muscle GLUT-4 protein. Thus, when working at a high load with low glycogen concentrations, muscle glucose uptake is significantly higher in trained than in untrained muscle. This may be due to the higher GLUT-4 protein concentration in trained muscle.

AB - Endurance training increases muscle content of glucose transporter proteins (GLUT-4) but decreases glucose utilization during exercise at a given absolute submaximal intensity. We hypothesized that glucose uptake might be higher in trained vs. untrained muscle during heavy exercise in the glycogen-depleted state. Eight untrained subjects endurance trained one thigh for 3 wk using a knee-extensor ergometer. The subjects then performed two-legged glycogen-depleting exercise and consumed a carbohydrate-free meal thereafter to keep muscle glycogen concentration low. The next morning, subjects performed dynamic knee extensions with both thighs simultaneously at 60, 80, and until exhaustion at 100% of each thigh's peak workload. Glucose uptake was similar in both thighs during exercise at 60% of thigh peak workload. At the end of 80 and at 100% of peak workload, glucose uptake was on average 33 and 22% higher, respectively, in trained compared with untrained muscle (P < 0.05). Training increased the muscle content of GLUT-4 by 66% (P < 0. 05). At exhaustion, glucose extraction correlated significantly (r = 0.61) with total muscle GLUT-4 protein. Thus, when working at a high load with low glycogen concentrations, muscle glucose uptake is significantly higher in trained than in untrained muscle. This may be due to the higher GLUT-4 protein concentration in trained muscle.

KW - Adaptation, Physiological

KW - Adult

KW - Exercise/physiology

KW - Glucose/metabolism

KW - Glucose Transporter Type 4

KW - Glycogen

KW - Human skeletal muscle

KW - Leg

KW - Male

KW - Monosaccharide Transport Proteins/metabolism

KW - Muscle Proteins

KW - Muscle, Skeletal/metabolism

KW - Physical Education and Training

KW - Physical Endurance/physiology

KW - Reference Values

KW - Thigh

U2 - 10.1152/jappl.2000.89.3.1151

DO - 10.1152/jappl.2000.89.3.1151

M3 - Journal article

C2 - 10956363

SN - 8750-7587

VL - 89

SP - 1151

EP - 1158

JO - Journal of Applied Physiology

JF - Journal of Applied Physiology

IS - 3

ER -