Dr Glenn McConell chats with Professor Jørgen Jensen from the Norwegian School of Sport Sciences about Carbohydrate and protein requirements of endurance athletes. He has over 30 years of experience examining these areas. We focussed on muscle glycogen depletion during exercise and glycogen resynthesis after exercise. He thinks no mechanistic link between glycogen content and fatigue. Also discussed combined carbohydrate and protein ingestion and protein requirements for endurance athletes. A short discussion on his work with caffeine and exercise and his current research.

0:00. Introduction and how Jørgen got into research
3:25. His initial glycogen metabolism research
Started off looking at rodent muscles.
5:15. Glycogen depletion and performance
His feeling is that muscle glycogen at exhaustion is still not fully depleted (both in rodent studies and in humans).
7:17. Glycogen deletion in different fiber types
Does muscle glycogen become depleted in type 1 muscle fibers during prolonged exercise? Different methods for measuring muscle glycogen in different muscle fiber types. Type 1 fibers recruited first but they don’t run out of glycogen.
12:25. No mechanistic link b/w glycogen content and fatigue
What about localization of glycogen within the cell? Some people fatigue during prolonged exercise with quite a lot of muscle glycogen remaining.
15:18. Low glycogen and glucose uptake w/o exercise
Total Glut-4 glucose transporter number and low glycogen. Insulin.
18:30. Fasting and muscle glycogen
Fasting rats increases Glut-4. Fasting and weight loss.
21:00. Why fatigue when ingest CHO during prononged exercise?
Protective mechanisms?
24:31. Glycogen resynthesis after exercise
Glycogen supercompensation. Recovery of performance after glycogen depleting exercise.
25:49. CHO vs CHO + protein after exercise
Perform better with the added protein if the exercise is exhausted. CHO vs CHO + protein and muscle glycogen resynthesis. Also protein synthesis.
31:08. Matching caloric expenditure to intake
Matching caloric expenditure to intake after prolonged exercise. CHO, protein and fat. Food vs CHO and protein powders etc.
34:27. Glycogen supercompensation
Glycogen supercompensation with diet and exercise training.
38:09. Glycogen synthase and glycogen resynthesis
Exercise activates glycogen synthase and it stays activated even when a lot of glycogen has been resynthesis.
41:41. Protein requirements for endurance athletes
He thinks athletes can get the protein they need from food. Unless they have done many hours of exercise consuming mainly CHO. Also adding protein fairly quickly after extremely hard exercise improves later exercise and recovery. If not very hard exercise it does not.
49:08. What things have gone wrong in the lab?
50:46. Caffeine and exercise
He finds caffeine improves performance, even increasing VO2 max in elite runners. Perhaps due to the higher max heart rate and max ventilation.
56:08. Amazing recent Norwegian athletes
Mens 400m hurdles Karsten Warholm. Mens 1500m and 5000m Jakob Ingebrigtsen.
Mentioned Australian legend marathoner Derek Clayton.
58:01. Exercise and glucose tolerance
Effect of timing after the last bout of exercise and glucose tolerance. Continuous glucose monitoring.

Inside Exercise brings to you the who's who of exercise metabolism, exercise physiology and exercise’s effects on health. With scientific rigor, these researchers discuss popular exercise topics while providing practical strategies for all.

The interviewer, Emeritus Professor Glenn McConell, has an international research profile following 30 years of Exercise Metabolism research experience while at The University of Melbourne, Ball State University, Monash University, the University of Copenhagen and Victoria University.

He has published over 120 peer reviewed journal articles and recently edited an Exercise Metabolism eBook written by world experts on 17 different topics (https://link.springer.com/book/10.1007/978-3-030-94305-9).

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