Nutrition and exercise Flashcards
What are the two main determinants of fuel use during exercise?
> intensity
> duration
What is the effect of exercise intensity on fuel use?
Increase intensity = greater muscle glycogen oxidation
- (van Loon et al, 2001)
What is the effect of exercise duration on fuel use?
Increase duration = greater plasma free fatty acid oxidation
- (Romjin et al, 2001)
Roughly how many calories of carbohydrate energy is stored within the human body?
<3,200 kcal
Roughly how many calories of fat energy is stored within the human body?
> 100,000 kcal
The concentration of what in the liver and blood is positively correlated with time to fatigue in endurance exercise?
glycogen
liver glycogen - (Casey et al, 2000)
muscle glycogen - (Bergstrom et al, 1967)
What 2 hormones stimulate gluconeogenesis and glycogenolysis in the liver when the body is in a fasted state or during exercise?
> adrenaline
> glucagon
Adrenaline suppresses the release of what hormone associated with liver glycogen regulation?
insulin
What effect does endurance training have on fasted levels of muscle glycogen?
increases them
- (Gonzalez et al, 2016)
What effect does a high carbohydrate diet have on endurance performance and why?
high CHO diet = increase muscle glycogen = increased time to fatigue
Why may carbohydrate be ingested during endurance exercise?
keeps blood glucose levels steady, preventing hypoglycaemia
So more carbohydrate ingested during exercise the better?
no,
as quantity ingested rises, utilisation rates drop
At what value of CHO ingestion during exercise does utilisation plateau?
~ 1 g per minute
What is the limiting factor for glucose utilisation?
glucose transporters in the intestine
SGLT 1 have a limit of 1.2 g per minute
What effect can glucose build up in the intestinal lumen have on a performer?
creates gut discomfort
How can you solve the problem of SGLT having a limit of 1.2 g per minute?
Ingest sucrose (glucose + fructose) glucose and fructose use different transporters, raising the uptake limit to 1.7 g per minute.
What happens to MUSCLE glycogen pre-post cycling exercise when ingesting water, glucose and sucrose
Water = drop Glucose = drop Sucrose = drop by similar amounts - (Gonzalez et al, 2015)
What happens to LIVER glycogen pre-post cycling exercise when ingesting water, glucose and sucrose
Water = drop Glucose = no change Sucrose = no change
- (Gonzalez et al, 2015)
In the Gonzalez et al 2015 study, what effect did ingesting sucrose have on substrate utilisation and gut discomfort compared with glucose?
Sucrose = increased energy from exogenous CHO utilisation and reduced gut discomfort
When either a placebo, glucose of sucrose drink was consumed 2 hours prior to a 1 hour cycling time trial, which condition resulted in greater average power output?
sucrose > glucose > placebo
- (Currell & Jeukendrup, 2008)
What is the optimal level of CHO ingestion for performance in endurance exercise?
1 - 1.5 g per minute at regular intervals (every 15 mins)
- (Smith et al, 2013)
When in a fed state, which hormone regulates liver glycogen?
Insulin
What effect does insulin have on liver glycogen?
increases stores by stimulating glycogen synthesis and suppressing glycogenolysis and gluconeogenesis.
In the days following exercise, what kind of recovery pattern does muscle glycogen follow?
supercompensation
