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Glucose and lactate interrelations during moderate-intensity exercise in humans
W C Stanley1, J A Wisneski, E W Gertz
1Department of Medicine, University of California, San Francisco.
Metabolism: Clinical and Experimental
|September 1, 1988
Summary
During moderate exercise, lactate production significantly increases, with its appearance rate nearly matching glucose disappearance. A substantial portion of blood lactate originates from muscle glycogen, not just blood glucose.
Area of Science:
- Exercise Physiology
- Metabolic Kinetics
- Biochemistry
Background:
- Understanding substrate utilization during exercise is crucial for optimizing athletic performance and metabolic health.
- Lactate and glucose kinetics are key indicators of energy metabolism during physical activity.
Purpose of the Study:
- To investigate the dynamic interplay between circulating lactate and glucose during moderate-intensity exercise.
- To quantify the rates of glucose disappearance and lactate appearance and their relationship.
Main Methods:
- Utilized stable isotopic tracer techniques ([13C]-lactate, [14C]-glucose, and vice versa) in ten healthy endurance-trained men.
- Measured arterial glucose and lactate concentrations at rest and during supine cycle ergometer exercise.
- Calculated rates of glucose disappearance (RdG) and lactate appearance (RaL) using tracer data.
Main Results:
- During exercise, the rate of lactate appearance (RaL) increased significantly, becoming 103% of the rate of glucose disappearance (RdG).
- Lactate clearance rate from the blood doubled during exercise compared to rest.
- An estimated 20% of glucose utilization contributed to lactate formation, with 20% of blood lactate originating from blood glucose.
Conclusions:
- Moderate exercise dramatically alters lactate and glucose metabolism, with lactate production rising substantially.
- Muscle glycogen is a primary source of blood lactate during exercise, exceeding contributions from blood glucose.
- These findings provide insights into fuel utilization strategies during endurance activities.