Nutrition & Athletic Performance Flashcards
Nutrition plays an essential role in exercise and sport because it is important for:
- health
- adaptations to PA and exercise
- weight maintenance
- exercise performance
Nutrition influences nearly every process in the body involved in:
- energy production
- recovery from exercise
Timing and amount of intake of macronutrients in the athlete’s diet should be based on a fundamental understanding of:
- how training-nutrient interactions affect energy systems
- substrate availability
- training adaptations
Exercise is fuelled by an integrated series of energy systems:
- ATP-PCr
- glycolysis
- aerobic
ATP-PCr system:
provide a rapidly available energy source for muscular contraction for ~10 seconds
Anaerobic glycolytic pathway:
- rapidly metabolizes glucose and muscle glycogen
- primary pathway supporting high intensity exercise lasting 10-180 seconds
As _____ becomes more available to the working muscle, the body uses more of the _____ pathways and less of the _____ pathways.
- oxygen
- aerobic (oxidative)
- anaerobic (phosphagen and glycolytic)
Oxidative pathways provide the primary fuels for events lasting longer than ______.
~2 minutes
Oxidative pathways use:
- muscle and liver glycogen
- intramuscular lipid
- adipose tissue
- triglycerides and AA from muscle, blood, liver and the gut
When crossover between pathways occur, the relative contribution of energy pathways is determined by:
- intensity, duration, frequency, and type of training
- sex and training level of the individual
- prior nutrient intake and substrate availability
6 components of diet:
- carbohydrate
- protein
- fat
- vitamins
- minerals
- water
Carbs can influence:
- performance
- adaptation to training
Modern carb intake recommendations are….
not one size fits all
Carb intake should be a function of …..
carb use or needs
Carb daily needs/recommendations depend on:
- characteristics of the exercise session
- body weight (proxy for the size of muscle stores)
General fuelling up guidelines:
- preparation for events <90 min exercise
- 7-12 g/kg per 24 h as for daily fuel needs
What type of carbs for general fuelling up?
- carb rich sources
- low in fibre
- easily consumed to ensure that fuel targets are met
- meet goals for gut comfort or lighter racing weight
Carb loading guidelines:
- prep for events >90 min of sustained/intermittent exercise
- 26-48 h of 10-12 g/kg body weight per 24 h
Speedy refuelling guidelines:
- <8 h recovery between 2 fuel demanding sessions
- 1-1.2 g/kg/h for first 4 h then resume daily fuel needs
What type of carbs for speedy refuelling?
- there may be benefits in consuming small regular snacks
- carb rich foods and drink may help to ensure that fuel targets are met
Pre-event fuelling guidelines:
- before exercise > 60 min
- 1-4 g/kg consumed 1-4 h before exercise
What types of carbs for pre-event fuelling?
- timing, amount, type of carb foods and drinks should be chosen to suit the practical needs of the event and individual preference/experience
- choices high in fat/protein/fibre may need to be avoided to reduce risk of GI issues during event
- low glycemic index choices may provide a more sustained source of fuel for situations where carbs cannot be consumed during exercise
Scandinavian researchers discovered that muscle glycogen could be _____ by changes in _____ and _____.
- supercompensated
- diet
- exercise
Supercompensation protocol resutled in….
extremely high muscle glycogen concentration
Important potential disadvantages of supercompensation:
- hypoglycemia during the low carb period
- GI problems
- poor recovery when no carbs are ingested
- tenseness during a week without training
- increased risk of injury
- mood disturbances during the low-carb period
Because of the numerous disadvantages of the classical supercompensation protocol, studies have focused on….
a more moderate protocol that can achieve similar results
- training slowly reduced over a 6 day period
- first 3 days: 50% CHO diet
- last 3 days: 70% CHO diet
How does supercompensation work?
- inc. time to exhaustion (endurance capacity) by ~20%
- dec. time required to complete a set task (eg. time trial, endurance performance) by 2-3%
With supercompensation, the duration of exercise must be at least ___ minutes before performance benefits occur.
90
Supercompensation had no effect on….
- sprint performance and high-intensity exercise up to about 30 minutes
- at these high intensities, glycogen depletion is probably not the performance-limiting factor
Mechanisms by which CHO feeding during exercise may improve endurance performance:
- maintenance of blood glucose and high levels of carb oxidation
- glycogen sparing in the liver and possibly muscle
- promotion of glycogen synthesis during exercise
- affects motor skills
- affects the CNS
Carbs provide improvement in endurance and performance > ___ min of duration.
45
Amount of carbs needed during brief exercise (<45 min):
not needed
Amount of carbs needed during sustained high intensity exercise (45-75 min):
- small amounts including mouth rinse
- frequent contact of carb with mouth
Amount of carbs needed during endurance exercise including stop and start sports (1-2.5 h):
- 30-60 g/h
Amount of carbs needed during ultra endurance exercise (>2.5-3 h):
- up to 90 g/h
- products providing multiple transportable carbs achieve high rates of oxidation of carbs consumed during exercise
Type of CHO ingested can affect _____ and _____ ___ and consequently improve _____.
- absorption
- oxidation rates
- performance
Feeding a single CHO source at high rates saturate _____ and limits _____.
- transporters
- absorption
____ + _____ + ______ + _____ + _____ = more CHO absorbed, made available for oxidation.
- glucose
- fructose OR maltodextrin
- fructose OR glucose
- sucrose
- fructose
Effect of more CHO absorbed, made available for oxidation is attributed to ….
the separate transport mechanisms across the intestinal wall for glucose (SGLT1) and fructose (GLUT5)
Faster absorption ____ the amount of CHO in the ___ ____ = dec. ____ discomfort during exercise.
- decrease
- GI tract
- GI
Describe carb mouth rinse:
- CNS might sense the presence of carbs via receptors in the mouth and oral space
- sweet and non-sweet CHO were shown to activate regions in the brain associated with reward and motor control
- rinsing the mouth with a carbohydrate solution can enhance performance
Describe how mouth rinsing or ingesting small amounts of CHO play a role when high power output is required over 45-75 minutes.
non-metabolic role in enhancing performance by ~2-3%
Mouth rinse can be practical in a few situations:
- athlete cannot ingest any CHO because of GI problems
- energy intake needs to be restricted
In carb mouth rinse, ____ is not the key factor.
- sweetness
- artificial sweeteners do not affect performance
In carb mouth rinse, brain activity is specific to ____.
- carbohydrates
- other nutrients do not seem to affect performance
Purpose of CHO intake after PA:
replenish depleted stores of liver and muscle glycogen
Important factors in promoting restoration of muscle glycogen stores:
- timing of CHO intake
- rate of CHO ingestion
- type of CHO ingested
- ingestion of PRO and CHO after exercise
Glycogen synthesis (4-6 h) post exercise is dependent on _____ _____. Above ____ of carb intake, there is little or no further benefit.
- carb intake
- 1.2 g/kg bw/h
Ingestion of types of carbs have no effects on ____ ____.
glycogen synthesis
Fructose ingestion leads to lower rates of …
muscle glycogen synthesis after exercise compared with glucose or sucrose
Fructose must be converted to _____ in the ____ before it can be used for ____ synthesis in the muscle. This process takes time.
- glucose
- liver
- glycogen
____ rate and the ____ of glucose seem to be important factors for glycogen synthesis.
- absorption
- availability
Muscle glycogen is more restored with a ____ meal compared with a ____ meal.
- high GI meal
- low GI meal
____ or ____ CHO meal have the same effect.
- liquid
- solid