Endurance athletes and those who do a lot of cardio (eg. runners, cyclists, swimmers) have different nutritional needs compared to those who are trying to achieve strength and muscle hypertrophy.
00:31 What happens to a muscle during exercise
03:22 Glycogen and fat as ‘protein sparers’
03:42 Comparing a mixed, high carbohydrate and high fat diet for endurance training
05:06 Recovery after an endurance event
05:27 Role of protein during recovery
06:14 Take home points
Endurance exercise burns through a lot more calories (per unit of time) than resistance training, and the fuel needed to sustain cardio is predominantly glycogen utilised by the aerobic system. This is in contrast with resistance training which relies on mainly the Creatine Phosphate and the Glycogen-Lactic Acid system for short bursts of muscle power.
The body preferentially uses glycogen and fat for energy. While protein can be broken down to make glucose (a process called gluconeogenesis), this process is not as efficient as using glycogen or fat to produce ATP. That’s why glycogen and fat are referred to as ‘protein sparers’.
Athletes on a high carb diet start off with much higer levels of muscle glycogen prior to exercise. This higher levels of glycogen is associated with longer time to exhaustion as compared to a mixed or high fat diet. So for endurance, a high carb diet easily outperforms a mixed or high fat diet.
A high carb diet leads to faster recovery of muscle glycogen compared to a high fat or mixed diet
Studies have shown that a high protein diet does not improve performance, but can improve blood markers of muscle damage and subjective muscle soreness.
Take home points:
1. Endurance athletes should focus on a high carb diet, with one study recommending 6-10g/kg/day of carbs.
2. It takes 48 hours to build up muscle glycogen stores even on a high carb diet. So it is better to avoid strenuous exercise for at least 2 days prior to a endurance event.
3. Protein may assist with recovery. One study recommends an intake of 0.25 g/kg of protein per hours of endurance exercise.
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Guyton and Hall Textbook of Medical Physiology 13ed (2015), chapter 85 (p1085-89)
International Society of Sports Nutrition Position Stand 2017: https://jissn.biomedcentral.com/articles/10.1186/s12970-017-0177-8
Macdermid et al. 2006: https://www.ncbi.nlm.nih.gov/pubmed/16676704?dopt=Abstract
Burke et al. 2011: https://pubmed.ncbi.nlm.nih.gov/21660838-carbohydrates-for-training-and-competition/
Saunders et al. 2007: https://pubmed.ncbi.nlm.nih.gov/17685703-consumption-of-an-oral-carbohydrate-protein-gel-improves-cycling-endurance-and-prevents-postexercise-muscle-damage/
Saunders et al. 2004: https://pubmed.ncbi.nlm.nih.gov/15235331-effects-of-a-carbohydrate-protein-beverage-on-cycling-endurance-and-muscle-damage/
Certain vector illustration adapted from https://www.freepik.com/
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