What Is the Evidence That Dietary Macronutrient Composition Influences Exercise Performance? A Narrative Review
The introduction of the needle muscle biopsy technique in the 1960s allowed muscle tissue to be sampled from exercising humans for the first time. The finding that muscle glycogen content reached low levels at exhaustion suggested that the metabolic cause of fatigue during prolonged exercise had bee...
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| Format: | Article |
| Language: | English |
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MDPI AG
2022-02-01
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| Series: | Nutrients |
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| Online Access: | https://www.mdpi.com/2072-6643/14/4/862 |
| _version_ | 1797477466041745408 |
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| author | Timothy David Noakes |
| author_facet | Timothy David Noakes |
| author_sort | Timothy David Noakes |
| collection | DOAJ |
| description | The introduction of the needle muscle biopsy technique in the 1960s allowed muscle tissue to be sampled from exercising humans for the first time. The finding that muscle glycogen content reached low levels at exhaustion suggested that the metabolic cause of fatigue during prolonged exercise had been discovered. A special pre-exercise diet that maximized pre-exercise muscle glycogen storage also increased time to fatigue during prolonged exercise. The logical conclusion was that the athlete’s pre-exercise muscle glycogen content is the single most important acutely modifiable determinant of endurance capacity. Muscle biochemists proposed that skeletal muscle has an obligatory dependence on high rates of muscle glycogen/carbohydrate oxidation, especially during high intensity or prolonged exercise. Without this obligatory carbohydrate oxidation from muscle glycogen, optimum muscle metabolism cannot be sustained; fatigue develops and exercise performance is impaired. As plausible as this explanation may appear, it has never been proven. Here, I propose an alternate explanation. All the original studies overlooked one crucial finding, specifically that not only were muscle glycogen concentrations low at exhaustion in all trials, but hypoglycemia was also always present. Here, I provide the historical and modern evidence showing that the blood glucose concentration—reflecting the liver glycogen rather than the muscle glycogen content—is the homeostatically-regulated (protected) variable that drives the metabolic response to prolonged exercise. If this is so, nutritional interventions that enhance exercise performance, especially during prolonged exercise, will be those that assist the body in its efforts to maintain the blood glucose concentration within the normal range. |
| first_indexed | 2024-03-09T21:18:03Z |
| format | Article |
| id | doaj.art-a2e012b370af44b080e1a87f74662c7c |
| institution | Directory Open Access Journal |
| issn | 2072-6643 |
| language | English |
| last_indexed | 2024-03-09T21:18:03Z |
| publishDate | 2022-02-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Nutrients |
| spelling | doaj.art-a2e012b370af44b080e1a87f74662c7c2023-11-23T21:29:32ZengMDPI AGNutrients2072-66432022-02-0114486210.3390/nu14040862What Is the Evidence That Dietary Macronutrient Composition Influences Exercise Performance? A Narrative ReviewTimothy David Noakes0Department of Applied Design, Cape Peninsula University of Technology, Cape Town 8000, South AfricaThe introduction of the needle muscle biopsy technique in the 1960s allowed muscle tissue to be sampled from exercising humans for the first time. The finding that muscle glycogen content reached low levels at exhaustion suggested that the metabolic cause of fatigue during prolonged exercise had been discovered. A special pre-exercise diet that maximized pre-exercise muscle glycogen storage also increased time to fatigue during prolonged exercise. The logical conclusion was that the athlete’s pre-exercise muscle glycogen content is the single most important acutely modifiable determinant of endurance capacity. Muscle biochemists proposed that skeletal muscle has an obligatory dependence on high rates of muscle glycogen/carbohydrate oxidation, especially during high intensity or prolonged exercise. Without this obligatory carbohydrate oxidation from muscle glycogen, optimum muscle metabolism cannot be sustained; fatigue develops and exercise performance is impaired. As plausible as this explanation may appear, it has never been proven. Here, I propose an alternate explanation. All the original studies overlooked one crucial finding, specifically that not only were muscle glycogen concentrations low at exhaustion in all trials, but hypoglycemia was also always present. Here, I provide the historical and modern evidence showing that the blood glucose concentration—reflecting the liver glycogen rather than the muscle glycogen content—is the homeostatically-regulated (protected) variable that drives the metabolic response to prolonged exercise. If this is so, nutritional interventions that enhance exercise performance, especially during prolonged exercise, will be those that assist the body in its efforts to maintain the blood glucose concentration within the normal range.https://www.mdpi.com/2072-6643/14/4/862muscle glycogenliver glycogenhypoglycaemiafatigueendurancediet |
| spellingShingle | Timothy David Noakes What Is the Evidence That Dietary Macronutrient Composition Influences Exercise Performance? A Narrative Review Nutrients muscle glycogen liver glycogen hypoglycaemia fatigue endurance diet |
| title | What Is the Evidence That Dietary Macronutrient Composition Influences Exercise Performance? A Narrative Review |
| title_full | What Is the Evidence That Dietary Macronutrient Composition Influences Exercise Performance? A Narrative Review |
| title_fullStr | What Is the Evidence That Dietary Macronutrient Composition Influences Exercise Performance? A Narrative Review |
| title_full_unstemmed | What Is the Evidence That Dietary Macronutrient Composition Influences Exercise Performance? A Narrative Review |
| title_short | What Is the Evidence That Dietary Macronutrient Composition Influences Exercise Performance? A Narrative Review |
| title_sort | what is the evidence that dietary macronutrient composition influences exercise performance a narrative review |
| topic | muscle glycogen liver glycogen hypoglycaemia fatigue endurance diet |
| url | https://www.mdpi.com/2072-6643/14/4/862 |
| work_keys_str_mv | AT timothydavidnoakes whatistheevidencethatdietarymacronutrientcompositioninfluencesexerciseperformanceanarrativereview |