During prolonged exercise,
During prolonged exercise, muscle and liver glycogen stores are depleted (the amount of glycogen stores you have in your body depends on your diet...carb rich diet will result in higher levels of stored muscle glycogen).
Depletion of glycogen and carbs (blood glucose) will result in a decreased rate of glycolosis (anaerobic pathway of producing energy) which in turn decreases the production rates of pyruvic acid/pyruvate (biproduct of glycolosis).
If pyruvate isn't available in the muscle, the availability of Kreb's cycle intermediates (oxaloacetate, malate etc) is reduced and the ATP production through Kreb's (aerobic metabolism..prolonged submaximal exercise) is slowed and less energy is available to the muscle.
Fats, in the form of fatty acids can be used in energy production. However, fat metabolism can ONLY occur through Krebs cycle. When the Krebs is slowed (reduced Krebs intermediates) so is the rate at which fat is metabolized.
Consuming carbs during exercise promotes the preservation of the liver stores of glycogen (converted to glucose thus providing blood glucose). It takes roughly 1hr (and this varies from individual) for muscle glycogen to be depleted (muscle glycogen = main source of carbohydrates for energy for the first hour). In addition, when blood glucose and liver glycogen stores are depleted, the body experiences hypoglycemia which inhibits central nervous system activation.
Another consideration is intensity level, if you are performing/training at higher intensity levels (as one may during a race) there is a shift from fats as fuels to carbohydrates. Fats are primarily used during low intensity exercise. If you try to pick up the pace during a prolonged exercise without the use of exergonic fuel/carbs you may hit your wall because there will be little blood glucose, muscle or liver glycogen left to fuel the higher intensity exercise.
Lastly, depending on where and when you are training environment will have an effect on your performance. It's likely that you are sweating and need to replace sodium lost through sweat. Sodium loss can lead to fatigue as well.
My guess is that you may not have the right fuel souce for you. Most recommendations say to consume 30-60g of carbs per hour of exercise, 1-5g/kg body weight 1-4hrs before exercise
Lots to consider. Try honey mixed with molasses and salt about an hour in. Seems to work well for me
During prolonged exercise, muscle and liver glycogen stores are depleted (the amount of glycogen stores you have in your body depends on your diet...carb rich diet will result in higher levels of stored muscle glycogen).
Depletion of glycogen and carbs (blood glucose) will result in a decreased rate of glycolosis (anaerobic pathway of producing energy) which in turn decreases the production rates of pyruvic acid/pyruvate (biproduct of glycolosis).
If pyruvate isn't available in the muscle, the availability of Kreb's cycle intermediates (oxaloacetate, malate etc) is reduced and the ATP production through Kreb's (aerobic metabolism..prolonged submaximal exercise) is slowed and less energy is available to the muscle.
Fats, in the form of fatty acids can be used in energy production. However, fat metabolism can ONLY occur through Krebs cycle. When the Krebs is slowed (reduced Krebs intermediates) so is the rate at which fat is metabolized.
Consuming carbs during exercise promotes the preservation of the liver stores of glycogen (converted to glucose thus providing blood glucose). It takes roughly 1hr (and this varies from individual) for muscle glycogen to be depleted (muscle glycogen = main source of carbohydrates for energy for the first hour). In addition, when blood glucose and liver glycogen stores are depleted, the body experiences hypoglycemia which inhibits central nervous system activation.
Another consideration is intensity level, if you are performing/training at higher intensity levels (as one may during a race) there is a shift from fats as fuels to carbohydrates. Fats are primarily used during low intensity exercise. If you try to pick up the pace during a prolonged exercise without the use of exergonic fuel/carbs you may hit your wall because there will be little blood glucose, muscle or liver glycogen left to fuel the higher intensity exercise.
Lastly, depending on where and when you are training environment will have an effect on your performance. It's likely that you are sweating and need to replace sodium lost through sweat. Sodium loss can lead to fatigue as well.
My guess is that you may not have the right fuel souce for you. Most recommendations say to consume 30-60g of carbs per hour of exercise, 1-5g/kg body weight 1-4hrs before exercise
Lots to consider. Try honey mixed with molasses and salt about an hour in. Seems to work well for me
