Title

Training Decreases Muscle Glycogen Turnover During Exercise

Document Type

Article

Publication Date

10-1998

Publication Source

European Journal of Applied Physiology and Occupational Physiology

Abstract

The present study was undertaken to determine the effects of endurance training on glycogen kinetics during exercise. A new model describing glycogen kinetics was applied to quantitate the rates of synthesis and degradation of glycogen. Trained and untrained rats were infused with a 25% glucose solution with 6-3H-glucose and U-14C-lactate at 1.5 and 0.5 μCi · min−1(where 1 Ci = 3.7 × 1010 Bq), respectively, during rest (30 min) and exercise (60 min). Blood samples were taken at 10-min intervals starting just prior to isotopic infusion, until the cessation of exercise. Tissues harvested after the cessation of exercise were muscle (soleus, deep, and superficial vastus lateralis, gastrocnemius), liver, and heart. Tissue glycogen was quantitated and analyzed for incorporation of 3H and 14C via liquid scintillation counting. There were no net decreases in muscle glycogen concentration from trained rats, whereas muscle glycogen concentration decreased to as much as 64% (P < 0.05) in soleus in muscles from untrained rats after exercise. Liver glycogen decreased in both trained (30%) and untrained (40%) rats. Glycogen specific activity increased in all tissues after exercise indicating isotope incorporation and, thus, glycogen synthesis during exercise. There were no differences in muscle glycogen synthesis rates between trained and untrained rats after exercise. However, training decreased muscle glycogen degradation rates in total muscle (i.e., the sum of the degradation rates of all of the muscles sampled) tenfold (P < 0.05). We have applied a model to describe glycogen kinetics in relation to glucose and lactate metabolism during exercise in trained and untrained rats. Training significantly decreases muscle glycogen degradation rates during exercise.

Inclusive pages

479–486

ISBN/ISSN

0301-5548

Comments

Permission documentation on file.

Publisher

Springer

Volume

78

Issue

6

Peer Reviewed

yes

Link to Full Text

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