Postmarathon paradox: Insulin resistance in the face of glycogen depletion

Juha A. Tuominen, Pertti Ebeling, Raymond Bourey, Laszlo Koranyi, Antti Lamminen, Juhani Rapola, Timo Sane, Helena Vuorinen-Markkola, Veikko A. Koivisto

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52 Scopus citations


Acute physical exercise enhances insulin sensitivity in healthy subjects. We examined the effect of a 42-km marathon run on insulin sensitivity and lipid oxidation in 19 male runners. In the morning after the marathon run, basal serum free fatty acid concentration was 2.2-fold higher, muscle glycogen content 37% lower (P < 0.01), glycogen synthase fractional activity 56% greater (P < 0.01), and glucose oxidation reduced by 43% (P < 0.01), whereas lipid oxidation was increased by 55% (P < 0.02) compared with the control study. During euglycemic-hyperinsulinemic clamp, whole body glucose disposal was decreased by 12% (P < 0.01) because of a 36% lower glucose oxidation rate (P < 0.05), whereas the rate of lipid oxidation was 10-fold greater (P < 0.02) than in the control study. After the marathon, muscle glycogen content correlated positively with lipid oxidation (r = 0.60, P < 0.05) and maximal aerobic power (V̇O(2peak); r = 0.61, P < 0.05). V̇O(2peak) correlated positively with basal lipid oxidation (r = 0.57, P < 0.05). In conclusion, 1) after the marathon run, probably because of increased lipid oxidation, the insulin-stimulated glucose disposal is decreased despite muscle glycogen depletion and the activation of glycogen synthase; 2) the contribution of lipid oxidation in energy expenditure is increased in proportion to physical fitness; 3) these adaptations of fuel homeostasis may contribute to the maintenance of physical performance after prolonged exercise.

Original languageEnglish
Pages (from-to)E336-E343
JournalAmerican Journal of Physiology - Endocrinology and Metabolism
Issue number2 33-2
StatePublished - 1996


  • exercise
  • glucose uptake
  • glycogen
  • glycogen synthase
  • insulin sensitivity
  • lipid metabolism


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