Wk 2 Carbs Flashcards
Metabolic pathways
Fats, carbs, proteins –> ?
Fats → FFAs + glycerol
Carbs → glucose
Proteins → amino acids
of calories per gram - carbs
4 kcals
Classification of carbs is based on number of _ _ _
Single sugar units
Sugars (1-2)
Monosaccharides
Disaccharides
Sugar alcohols
Oligosaccharides (3-10)
Malto-oligosaccharides
Non-a-glucan oligosaccharides
Polysaccharides (>10)
Starch
Fiber
Monosaccharides
Glucose, fructose, galactose
Disaccharides
Sucrose, maltose, lactose
Sugar alcohols
Sorbitol, mannitol, malitol
Malto-oligosaccharides
Maltodextrins
Non-a-glucan oligosaccharides
Inulin, polydextrose, raffinose
Starches
Amylose, amylopectin, modified starch
Fibers
Cellulose, pectin, B-glucan
Characteristics of high quality complex carbs
minimally processed, contains all nutrients and fiber, made of the whole grain (bran, endosperm and germ)
Characteristics of low quality complex carbs
extensively processed to remove bran and germ, much less fiber and fewer naturally occurring vitamins and minerals than high quality carbs
Role of carbs in exercise
Important role for performance in; prolonged, intermittent intensity and high intensity exercise, and for recovery in sport.
Carbs for exercise - location, amount and notes
Liver; 75-100g. Supports blood glucose level at rest and during exercise, depleted by overnight fast to <20g.
Muscle; 300-400g. Supplies glucose for muscle - lacks G6P, use increases with exercise intensity. Depletion: depends on exercise intensity
Blood; 4g blood glucose (3.9-5.5 mmol/L). Used by brain (and exercising muscle, as muscle glycogen becomes depleted)
Carb reserves are ___ g - ____ kcals
Carb reserves are 500g - 2000cal
Fat reserves are…
Almost unlimited
Roles of CHO in the athletes diet
Carbs sustain daily training, health and wellbeing, replenish liver and muscle glycogen stores, requirements vary depending on training intensity and duration, should be consumed throughout the day, should be altered day by day to reflect training load,
Training load and CHO intake (g/kg/d):
light - 3-5 (low intensity/skill based), moderate (60 min) - 5-7, endurance (1-3 hr of moderate/high) - 6-10, extreme (>4-5 hr mod/high) - 8-12
Sedentary people need _ g CHO every day.
Sedentary people 130g CHO every day.
Training with low carb stores leads to…
Increase in signalling enzyme AMPK - stimulates energy generating processes; decreases energy consuming processes. Activates transcriptional factors and co activators - PGCs. upregulates expression of genes related to mitochondrial biogenesis, and angiogenesis. Carb essentially switches off AMPK activation.
Low carb training - types and methods
Training 2x per day; limited or no carb intake between two training sessions - may incr expression of relevant genes
Training fasted; training after an overnight fast. Muscle glycogen may be ok but liver glycogen will be low.
Training w low exogenous carb availability; little or no carb ingested during exercise. This will exaggerate the stress response
Withholding carbs during recovery; none or very little carb post exercise to prolong the stress response
Sleep low; train late in the day with no carb before sleep. Lowers liver and muscle glycogen for several hours
Low carb training - drawbacks
possible negative impact on muscle protein synthesis. Will impact work capacity and quality of high intensity training sessions. May impact the immune system. Not advisable for athletes under 18. Psychological effects.
Pre-exercise meal - objectives
Incr/replenish muscle glycogen, restore liver glycogen after an overnight fast
Contribute to hydration, prevent hunger, easily digested, psychological boost?
Pre-exercise meal - guidelines
- Main meal 2-3 hrs before exercise lasting >60 min; to allow for gastric emptying before exercise
- Provide 1-4g CHO/kg before exercise - restore liver glycogen. increase/replenish muscle glycogen
- Contain fluid - contribute to hydration
- Avoid very high fat and spicy foods - facilitate gastric emptying, minimize GI distress
- Moderate in protein - filling?
- 30-60 min before exercise top up with high GI carbs - quick source of glucose
CHO during exercise - types of exercise w/ timing and corresponding CHO
- Brief exercise - <45 min: not required
- Sustained high intensity exercise - 45-75 min: small amounts incl mouth rinse for 10s, consider dental hygiene
- During endurance exercise incl stop and start sports - 1-2.5 hr: 30-60 g/h to spare muscle glycogen and maintain BG levels
- Ultra endurance exercise - <2.5-3 hr: up to 90 g/h. Use of different intestinal transporters may incr overall CHO absorption. Maltodextrin - fructose, glucose - fructose, glucose - sucrose - fructose
