Ten days of exercise training reduces glucose production and utilization during moderate-intensity exercise

Abstract

We have previously shown that 12 wk of endurance training reduces the rate of glucose appearance (Ra) during submaximal exercise (Coggan, A. R., W. M. Kohrt, R. J. Spina, D. M. Bier, and J. O. Holloszy. J. Appl. Physiol. 68: 990-996, 1990). The purpose of the present study was to examine the time course of and relationship between training-induced alterations in glucose kinetics and endocrine responses during prolonged exercise. Accordingly, seven men were studied during 2 h of cycle ergometer exercise at approximately 60% of pretraining peak oxygen uptake on three occasions: before, after 10 days, and after 12 wk of endurance training. Ra was determined using a primed, continuous infusion of [6,6-2H]glucose. Ten days of training reduced mean Ra during exercise from 36.9 +/- 3.3 (SE) to 28.5 +/- 3.4 mumol.min-1.kg-1 (P < 0.001). Exercise-induced changes in insulin, C-peptide, glucagon, norepinephrine, and epinephrine were also significantly blunted. After 12 wk of training, Ra during exercise was further reduced to 21.5 +/- 3.1 mumol.min-1.kg-1 (P < 0.001 vs. 10 days), but hormone concentrations were not significantly different from 10-day values. The lower glucose Ra during exercise after short-term (10 days) training is accompanied by, and may be due to, altered plasma concentrations of the major glucoregulatory hormones. However, other adaptations must be responsible for the further reduction in Ra with more prolonged training.

Glucose Turn Point as a Marker of Exercise Intensity in Elite Swimmers

“…The resting glucose for the thirty-three swimmers ranged between 4.5 and 6.7 mmol/l with a mean of 5.5 ± 0.57 mmol/l, which is in line with that previously observed in a training population [15] (Table 1). …”

“…Following the occurrence of Gt (4.8 ± 0.39 mmol/l), there was a significant rise in blood glucose through the following stages of the test, reaching its maximum (7.1 ± 1.1 mmol/l) at the point of highest effort Gt universally occurred at a lower exercise-intensity than AnT. This observation is supported by data from other researchers [6,[15][16][17][18][19] who, although not directly identifying Gt, have suggested that factors other than the production of lactate influence carbohydrate metabolism prior to AnT. Irrespective of the method used to identify AnT (Borch, Cheng or Kindermann) and the method used to compare differences (glucose, lactate, heart rate or time), Gt occurred at between 6 and 10% lower intensity than at AnT.…”

Effect of exercise and training on phospholemman phosphorylation in human skeletal muscle

“…During the trials, blood, expiratory gases, and skeletal muscle biopsies were taken. The short-term, 10-day training protocol has been effectively used to induce changes in exercise performance, metabolism, and muscle signaling in response to the same absolute intensity exercise by our group (2) and others (28,30).…”

Adrenergic-β2 receptor polymorphism and athletic performance

“…b-receptors facilitate lipolysis during exercise through the stimulation of sympathetic nervous system activity, which counteracts circulating insulin action on adipocytes during prolonged exercise. 18,54 Stimulation of the sympathetic nervous system through the onset of exercise promotes the release of catecholamines-epinephrine and norepinephrine. The b 2 -receptor subtype is more effective under epinephrine exposure.…”