Carbohydrate Supplementation Pre-exercise Flashcards
- Identify the most appropriate nutritional strategy in the lead-up of prolonged bout of physical activity - discuss the distinct mechanisms through which your specific recommendations might facilitate performance
What are the 2 main roles of CHO nutrition before exercise?
- Maximise CHO availability (CHO loading)
2. Ensure adequate hydration
What is the habitual diet for athletes?
10-15% protein
15-25% fat
60-70% carbohydrates
How does the CHO regimen work?
- Low CHO + hard training for 3 days = pushes muscle to store glycogen
- High CHO + low training = super compensation of glycogen storage
What is exercise capacity?
Time to exhaustion
What is the utility of measuring exercise capacity?
Understand fatigue
What is exercise performance?
How far athlete can go in a defined period of time
What is the Bergstrom et al. (1967) study ?
oExercise to exhaustion on cycle ergometer @75% VO2max
oOver 3 days prior to exercise participants ingested either: high fat/protein diet or mixed diet or high CHO diet
oMeasured how long they could go for
>High CHO diet is much more advantageous, longer time to fatigue
What is the Karlsson et al. (1971) study?
oTime to complete a 30km run
oOver 7 days prior to exercise participants ingested either mixed diet or high CHO diet
>High CHO is better, shorter time to complete run
What is the Pizza et al. (1995) study?
oExercise to exhaustion on treadmill @100% VO2max
oOver 3 days prior to exercise participants ingested either mixed diet or high CHO diet
oMeasured how long they can hold VO2max intensity
>Surprisingly high CHO is better, longer time to fatigue
What are the 2 effects of CHO ingestion 3-4 hours before competition?
- Increases liver/muscle glycogen concentrations
2. Provides a feeling of comfort and satiety
What is the Chryssanthopoulos et al. (1994) treadmill study?
oTime to complete a 30km treadmill run
oParticipants ingested either: CHO 4h Pre and H2O during or H2O pre and CHO during
oDuring exercise, CHO is liquid ingestion (6% CHO solution)
>No difference: as long as there is CHO ingestion before or during it is the same
What is the Wright et al. (1991) study?
oExercise to exhaustion on cycle ergometer @70% VO2max
oParticipants ingested either: no CHO, CHO 3h pre-ex, CHO during ex, CHO 3h pre + during ex
>In all times of feedings, CHO intake was helpful relative to no CHO
When is it ideal for athletes to ingest CHO?
Pre + during competition
What are the 3 effects of CHO ingestion within one hour before competition?
- Final pre-exercise boost for liver/muscle glycogen concentrations
- Provides an exogenous source of CHO as it empties from the stomach
- Can cause metabolic disturbances
Why don’t studies measure below 70% VO2max?
It represents athlete levels and is above fat oxidation rates
Why don’t studies measure over 75% VO2max?
Can lead to variations due to acidosis differences (lactate)
What are the 5 metabolic responses to glucose ingestion?
- Increased plasma glucose
- Increased plasma insulin
3a. Increased CHO metabolism
3b. Lower plasma glucose
4a. Increased glycogen utilisation
What is the Costill et al. (1977) study?
Glucose ingestion and glycogen metabolism
o30 min of treadmill running
o45 prior to exercise participants ingested either: 300ml H2O + 75g glucose or 300ml H2O alone (placebo)
oGlucose group: fasted state, glucose levels rise with feeing, then adrenaline response due to exercise reduce plasma glucose
>Rebound hypoglycaemia in glucose group (below fasted glucose levels)
>CHO group using muscle glycogen faster (seems like a waste in terms of performance)
What is the Foster et al. (1979) study?
Glucose ingestion and exercise capacity
oFollow-on study from Costill et al. (1977) findings translate on exercise capacity?
oExercise to exhaustion on cycle ergometer @80 VO2max
o30 min prior to exercise participants ingested either 300ml H2O + 75g glucose or 300ml H2O alone (placebo)
>Glucose group does worse
>Only paper to find - effect of CHO
What is the Chryssanthopoulos et al. (1994) cycle study?
oExercise to exhaustion on cycle ergometer @70 VO2max
o30 min prior to exercise participants ingested either 300ml H2O + 75g glucose or 300ml H2O alone (placebo)
>Found no difference, if anything betters CHO
What are the 2 solutions of metabolic disturbance?
- Ingesting different types of CHO can alter the metabolic response to that feeding
- Ingesting low GI carbs before exercise may minimise any transient metabolic disturbance
What is the Glycaemic Index?
The incremental area under the blood glucose response curve of a 50g CHO portion of a test food expressed as a percent of the response to the same amount of CHO from a standard food (usually glucose) taken by the same subject
What is the Glycaemic Index equation?
(IAUC of test food)/(IAUC of reference food)x100
in mmol.l-1.150min
What is the Thomas et al. (1991) study?
oExercise to exhaustion on cycle ergometer @65-70% VO2max
o1h prior to exercise participants ingested either: H2O (placebo), Lentils (LGI), Potato (HGI), glucose (HGI)
>Sig positive effect of LGI compared to other 3
