Creatine and Nitrate Flashcards
1
Q
what is creatine
A
- endogenously synthesised from AA (argenine, glycine and methionine) in the liver, pancreas and kidneys
- > 95% is stored in skeletal muscle
- approx… 50% obtained from the diet
2
Q
creatine stores
A
- about two thirds of intramuscular creatine is phosphocreatine (PCr) with the remaining being free creatine
- the total creatine pool (PCr + Cr) in the muscle averages about 120mmol/kg dry muscle mass
- the upper limit of creatine storage appears to be about 160mmol/kg dry muscle mass
- vegetarians have been reported to have lower intramuscular creatine stores (90-110 mmol/kg dm)
3
Q
creatine turnover
A
- synthesis - ~2g/day
- 1g endogenous
- 1g exogenous (diet)
- excretion - ~2g/day
- creatine (urine)
4
Q
what are the effects
A
- increase in PCr resynthesis
- short-term, high-intensity exercise capacity to perform repeated bouts of high-intensity effort
5
Q
creatine metabolism during exercise
A
- PCr levels higher in type II fibres than type I fibres
- PCr levels decrease during maximal exercise (because its breakdown sustains high rates of ATP production)
- PCr can be depleted in ~10 seconds
- 80% re-synthesised in ~4 minutes
6
Q
mechanisms of action
A
- supplementation with creatine:
- increase in Cr stores 30% = increase PCr resynthesis
- increase in muscle glycogen
- increase in growth factor expression
- increase in protein synthesis
- decrease in muscle damage
- training harder, longer = increase in lean mass / strength
7
Q
creatine sources
A
- diet (red meat [beef/pork] and some fish [tuna, salmon, cod, herring) -> but not enough
- creatine monohydrate (CM)
- white powder, 99% absorbed
- significant amount of evidence
- better uptake mixed with a carbohydrate containing liquid or food (consume quickly after mixing)
- synthetic (suitable for vegetarians and vegans)
8
Q
creatine loading protocols
A
- no acute effect -> loading protocols
- short, high-dose protocols:
- 20 g/day (split in 4 doses) for 5 days
- 0.3 g/kg BM (split in 3-4 doses) for 5 days
- long, low dose protocol:
- 3-5 g/day for 20-30 days
- maintenance dose:
- 2-5 g/day
- washout period = 4-6 weeks
9
Q
when to consider its use?
A
- single (+1-5%) and repeated bouts (+5-15%) of high-intensity exercise
- high-intensity max efforts <150sec, largest effects on <30sec tasks
- power and strength sports: 100m and 200m sprints, weightlifting, powerlifting, sprint swimming
- intermittent sports: field/team sports
- resistance/interval training: training programmes aiming to increase lean mass and muscular strength/power
10
Q
other applications
A
- endurance exercise
- recent evidence shows that a combination of creatine and CHO loading may increase power output during repeated high-intensity sprint efforts during the late stages of prolonged stimulated TT cycling
- concussion
- improvements in cognitive processing in the brain and potentially reduced damage and enhance recovery from mild traumatic brain injury/concussion
11
Q
individual variability
A
- baseline levels of muscle creatine
- individuals that have high muscle creatine levels will experience low creatine uptake from supplements, and vice-versa. Therefore, individuals with low muscle creatine levels (e.g. vegetarians) have the greatest potential for increases in response to supplementation
- sport type
- in sports where performance is not determined by PCr availability (or fast ATP resynthesis) creatine supplementation will likely not have any effects (e.g. ultra-endurance or exclusively skill-based)
12
Q
concerns
A
- increase in body mass (1-2kg)
- likely as result of water retention. It may be counteractive for the performance for endurance and/or other eight-sensitive sports. consider washout period (4-6 weeks) if using creatine
- myths
- there is no evidence that creatine supplementation causes kidney damage, muscle cramps, strains, damage/injury, or affects fluid balance and heat dissipation
13
Q
safety issues
A
- no evidence of adverse effects with long term (4 years) creatine supplementation at appropriate dosages in healthy individuals
- mild, temporary gut upset can occur but can be attenuated with split dose, longer loading protocol and avoidance of high fibre foods with ingestion
- contamination: all supplements have a doping risk of some kind. athletes should only use batch-tested supplements
14
Q
what is nitrate
A
- dietary nitrate (NO3-)
- the ingestion of NO3- leads to enhanced nitric ocide (NO) bioavailability
- high nitrate-containing foods include leafy greens and root vegetables
- the average dietary intake of adults in western countries is 1-2 mmol/d (~60-120 mg/d) with vegetables providing about 80% of the total
15
Q
Nitric Oxide (NO)
A
- ingestion of dietary NO3- -> enhanced NO bioavailability (via the No3- nitrate-NO pathway, reaction catalysed by bacteria in the mouth and the digestive system
- NO plays an important role in the modulation of skeletal muscle function
