exercise and GI function Flashcards
ingested fluid availability is dependant on which two factors
gastric emptying
intestinal absorption
which factors affect gastric emptying
gastric volume
energy density
osmolality
exercise intensity
what is the site at which most fluid and macronutrient absorption takes place
small intestine
what is the function of the microvilli
increase surface area for absorption
what factors affect intestinal absorption
%CHO
type of CHO
Na+ (glucose - sodium co transporters - SGLT1
osmolality
what determines optimum fluid intake
combination of ambient temp (sweat loss) and exercise intensity determine how much fluid and carbohydrate is necessary
how does a high cho concentration affect absorption of fluid
reduce absorption of fluid and hence fluid availability
high cho concentration leads to high osmolarity which causes net movement of water into intestinal lumen
this leads to a net loss of water and has a dehydration effect
how much fluid should be ingested before exercise to prevent hypohydration
4-600ml of fluid
what should cho content in fluid be during exercise?
high enough to provide substrate but not so high that osmolality becomes too high and water absorption is impeded
what are the hazards of exercise for GI tract
nausea, heart burn, diarrhoea, Gi bleeding, mechanical injury of organs
what are the long term risks of GI bleeding
Fe deficiency and anaemia
how can GI bleeding be avoided
avoidance of NSAIDS and dietary fluid intake
exercise may reduce the risk of which GI tract diseases
GI cancers, gallstones, GI haemorrage, inflammatory BD and constipation
how is exercise thought to reduce the risk of colon cancer
reducing intestinal transit time, thus lowering secondary bile acids and increasing faecal short chain fatty acids
also improve immune function, decrease bmi, decrease insulin resistance
how does exercise reduce the risk of gall stones
exercise linked to decreased weight and better diet
exercise acts against glucose tolerance, high serum insulin, TGs, low serum HDL to prevent gall stones
also regulates CCK
how does exercise affect the risk of IBD
IBD - not IBS!!!!!
ulcerative colitis and crohns disease
sedentary groups have higher incidence of IBD
patients with IBD take steriod drugs to help with symptoms but this causes muscle weakness and osteoporosis
exercise helps to reduce the effect of the steroids and hence can increase quality of life for these patients
how does exercise affect constipation
increased gut motility, decreased blood flow to gut
biomechanical bouncing of the gut and increased fibre intake as a result of increased EE
how does repeated high intensity exercise affect gut function
intense exercise 70%+ VO2 max - during exercise blood flow is diverted to heart and working muscles and away from digestive system - during intense exercise more blood is diverted away, almost 60-70% decrease in blood flow - resulting in temporary ischemia of the gut
long term repeated high intensity exercise can lead to tissue damage due to ischemia
what neuro/immuno/endocrine changed are caused by exercise
hormone levels change - CCK, secretin, noradrenaline, adrenaline, glucagon
boots immune function via various cells - macrophages, neutrophils, natural killer cells
severe exercise may possible reduce natural killer cells + increase free radicals but exercise increases production of antioxidants
why is glucose present in sports drinks
activation of the SGLT1 glucose-sodium transporters - increased intake of glucose and sodium
water follows salt
