SN - Carb 1

bethdrysdale94's version from 2017-03-27 21:30

Section 1

Question Answer
How are substrates metabolised during exercise?digestive tract > glycogen in liver (80g) > glucose in blood > glycogen in muscle (300-800g) > CO2. OR Triglycerides in adipose tissue (10000-15000g) > FFA in blood > triglycerides in muscle (300g) > CO2
Which substrates are metabolised at different exercise intensities?fat = mid > low > high. Plasma FFA = roughly equal in all. Plasma glucose = high > mid > low (doubles from low to high) and muscle glycogen = high > mid > low but drastic increase. most energy at high intensity comes from muscle glycogen
What effect does the rate of glycogen depletion have on time to fatigue?higher rate of depletion, shorter time to fatigue
Maintenance of plasma glucose does what to time to fatigue?increases time to fatigue but only a short amount (1hr out of 4hrs) once muscle glycogen is depleted
What effect does CHO-electrolyte feeding have on time trial performance?improves performance compared to placebo (jeukendrup 1997) by over a minute
Can you spare liver glycogen?Yes, high glucose feeding completely spares liver glycogen, low glucose mostly spares it whereas none doesn't
What happens when you feed above optimal glucose?oxidation rates stay the same in low to high amounts of glucose feeding, as you increase feeding, more gets emptied but not all of the leftover, so the rest will become stored

Section 2

Question Answer
What are the simple carbohydrates?glucose, fructose, maltose, lactose, sucrose, galactose
What are the complex carbs?Malto dextrin (one branch), Amylose starch (long chain) and amylopectin starch (multiple branches)

Section 3

Question Answer
how can you measure oxidation of CHO?ingest labelled CHO with 13C, collect breath samples, analyse ratio of 13CO2 to 12CO2 (isotope ratio)
what limiting factor of oxidation of ingested carbs?exogenous carb oxidation rate, NOT ingestion rate. limited to below 1.0g/min of carbs
What limits exogenous CHO oxidation?not gastric emptying, not muscle glucose uptake, but intestinal CHO absorptionis the rate limiting step
How are carbs digested and absorbed?broken down into glucose/galactose/fructose. fructose does not require transport, but glucose and galactose move through with sodium into capillary
How is glucose absorbed?SGLT1 moves glucose and sodium into cell, GLUT2 transported allows glucose out of cell into ECF/blood, active transport of potassium occurs to maintain negative potential to allow movement of sodium in with glucose
how is fructose absorbed?GLUT5 into cell and GLUT2 out of cell

Section 4

Question Answer
1.2g/min gluc vs 1.2g/min gluc and 0.6g/min fruc vs 1.8g/min gluc, on exogenous CHO oxidation rate1.2 and 1.8g/min gluc produced same result, limited to around 0.8g/min absorption. gluc and fruc combined exceeded 1.2g/min absorption
What are the recommendations of CHO consumption during exercise?1.0-1.2g/min during exercise (1.0L of sports drink/hour (6-7%) or 0.5L sports drink (6-7%) plus an energy bar/gel
What type of CHO is recommended?simple CHO = glucose or maltodextrin (not fructose). or combined = glucose or maltodextrin AND fructose
What are the effects of glucose and fructose on timetrial?glucose reduces time by 10%, glucose and fructose reduces time by a further 8%
When is there no placebo effect in CHO trials?during prolonged exercise. placebo and water were equivalent, CHO (6%) reduced time by 11%
Drink or energy bar?Drink was significantly greater than bar in oxidation over time
Does caffeine have an effect on substrate when ingested with CHO?no
Does caffeine have an effect on TT cycling performance?yes, 30mg/100ml of caffeine with 6.4% GLU was 4.6% better than just GLU and 9.0% better than placebo

Section 5

Question Answer
CHO ingestion during exercise enhances performance by maintaining plasma glucose conc. and high rates of CHO oxidation when..?muscle and liver glycogen levels are reduced
Higher rates of exogenous CHO oxidation can be achieved with...?ingestion of combined CHO sources (GLU+FRU)
Combining CHO and caffeine ingestion effective strategy to enhance performance