Splanchnic glucose and muscle glycogen metabolism after glucose feeding during postexercise recovery

Glucose (100 g) was ingested 15 min after bicycle exercise until exhaustion at a work load corresponding to 70% of maximal uptake (series 1), 14--15 h after an identical exercise period, no food being taken in the interval (series 2), and by nonexercised control subjects. Splanchnic glucose output in the exercised groups rose to values 50--300% greater than in controls, amounting to (over 135 min) 59 +/- 5 g in series 1 and 58 +/- 6 in series 2 compared to 28 +/- 6 in controls. The glycogen concentration of quadriceps muscle in series 1 was 65 +/- 2 mmol glycosyl U/kg wet wt before exercise, 16 +/- 13 at the end of work, and 32 +/- 4 at 135 min after glucose ingestion. In series 2, muscle glycogen concentration was 20 +/- 3 immediately after exercise and rose to 44 +/- 5 over the ensuing 14--15 h in spite of continued fasting. It rose to 56 +/- 3 at 135 min after glucose loading. Repletion of leg muscle glycogen after glucose feeding could account for 50--66% of total splanchnic glucose release. It is concluded that during postexercise recovery, a greater proportion of an oral glucose load escapes hepatic retention, allowing repletion of muscle glycogen to take precedence over hepatic glycogen repletion.