Carbohydrates during exercise (wk 3) Flashcards
What are the 6 types of carbohydrates?
-> Glucose, fructose, galactose, maltose, sucrose and lactose
Draw the graph for slow and fast carbohydrates:
-> ‘Fast’ and ‘Slow’ refers to the speed at which these carbohydrate types are digested, absorbed and made available to the body for energy provision
What are the updated guidelines for athletes:
-> New guidelines consider the duration (and intensity) of exercise. Important to consume the correct amount of carbohydrates and sugars so that it doesn’t sit in the stomach and cause indigestion
-Only a proportion of what you consume will be oxidised
Describe carbohydrate feeding during exercise:
-> Carbohydrate feeding during exercise of about 45 min or longer can improve endurance capacity and performance. Effects of carbohydrate feeding during exercise increase with exercise duration. Carbohydrate feeding may also benefit from other aspects of sport performance e.g. motor skills during prolonged sports events
Draw the timeline for duration of exercise, amount of carbs needed and recommended types of carbs:
Describe carbohydrate ingestion during exercise:
-> There is a fall in blood glucose and then plasma glucose and carbohydrate oxidation during exercise. To overcome this, there should be carbohydrate digestion to fuel the body to offset these problems
-When we consume carbohydrates during exercise, there is spared liver glycogen but it must be careful of the amounts consumed
What are the metabolic effects of carbohydrate feeding during exercise:
-> Maintains plasma glucose concentration and helps to sustain high rates of carbohydrate oxidation. Spares liver glycogen (helping to sustain plasma glucose and carbohydrate oxidation). May spare muscle glycogen, but not often observed.
-Mouth rinsing can have benefits in terms of CHO loading
What are dose-responses of ingested glucose at 120 min cycling, 65% VO2 max?
-> No significant change in high doses of ingested glucose with exogenous carbohydrate oxidation rate. This implies that there is an optimal limit with the relationship between doses of ingested glucose and exogenous carbohydrate oxidation rate.
Draw the possible non-metabolic effects:
Draw the absorption of carbohydrates:
What is the difference in performance with glucose vs glucose+fructose?
-> 9% faster with glucose+fructose compared to glucose, and 19% faster compared to water (placebo)
What is multiple transportable carbohydrates?
-> Multiple transportable carbohydrates refers to sugars that are transported across the intestine by stimulating more than one protein transporter e.g. glucose and fructose. This can increase exogenous carbohydrate oxidation by 20-50% above single transported carbohydrates (and it can improve gut comfort). In prolonged, intense exercise (>2.5-3h), this can contribute to further performance enhancement.
-For exercise lasting >60-90 minutes, the benefits are related to the metabolic effects of providing ‘fuel’ to the body. To achieve the high ingestion rates (up to 90h/h), recommended for sustained intense exercise of >2.5-3h, multiple transportable carbohydrates are needed.
Day-to-day vs short term recovery:
-Long term (8-24 hours) -> Adoption of general daily CHO intake should ensure repletion on day-to-day basis. Short term (0-8 hours) -> More specific strategies may help ensure rapid glycogen repletion.
Draw the general daily carbohydrate intake guidelines for athletes (light, moderate, high and very high):
What is glycogen synthase?
-Glycogen synthase can be trained and with a greater exercise duration and intensity, the more efficient and faster it works to replenish glycogen stores
What is the regulation of muscle glycogen synthesis? + draw the graph
-> When we eat there’s an insulin response which has a positive effect on the GLUT4 pool and the GLUT4 translocation
Draw the graph for glycogen synthesis and carbohydrate intake
Describe types of carbohydrates:
-> Carbohydrate-rich foods with a moderate-to-high glycaemic index provides a readily available source of substrate for glycogen synthesis. This may be important when maximum glycogen storage is required in the hours after an exercise bout. Glucose = 100%, sucrose = 65% and fructose 25% in the glycaemic concentration index.
What is the effect of speedy refueling after exercise?
-> Early and frequent carbohydrate feeding (e.g. within the first hour and at 30 min intervals for 4 h thereafter, before resuming normal diet). 1.2 g/kg CHO/h for first 4 hours, of moderate-to-high glycaemic index CHO’s. Addition of protein if CHO is sub-optimal (but probably some protein anyway for stimulation of MPS).
What is the effect of post-exercise fructose-glucose?
-> Glucose has a 6 hr synthesis rate of 3.7 +/- 0.5 g/h, whereas fructose-glucose has a 6 hr synthesis rate of 8.1 +/1 0.6 g/h in the liver glycogen. Glucose has a 4 h synthesis rate of 44 +/- 8 mmol/kg dm/h, whereas fructose-glucose has a 4 hr synthesis rate of 39 +/- 8 mmol/kg dm/h in the muscle glycogen.
Describe carbohydrate type and short-term exercise recovery:
-> The replenishment of glycogen stores can be accelerated when fructose is co-ingested alongside glucose-based carbohydrates. Fructose co-ingested with glucose in recovery from exercise can also enhance subsequent time-to-fatigue.
