Week 9 - Creatine Flashcards
Where is creatine synthesized?
endogenously synthesised from AA (arginine, glycine and methionine) in the liver, pancreas, and kidneys
Where is creatine stored?
> 95% stores in skeletal muscle
What % of creatine is obtained from diet?
50% - meat and fish
In what form is creatine stored in the muscle?
2/3 Phosphocreatine (PCr)
1/3 Free creatine
What is the average total creatine pool in muscles?
What about the upper limit of creatine storage?
120 mmol/kg dry muscle mass
160mmol/kg dry muscle mass
What is the average IM creatine stored in vegetarians?
90-110mmol/kg dry muscle
In terms of creatine turnover, how much is synthesized and how much is excreted?
Synthesis - 2g/day –> 1g endogenous + 1g exogenous (diet)
Excretion - 2g/day –> creatinine (urine)
During a 30sec cycling exercise bout, what are the benefits of increased creatine?
Maximal work and total work increases.
What does creatine enhance?
resistance to fatigue
What are the benefits of combining creatine supplementation and resistance training?
Hypertrophy - small increase of skeletal muscle hypertrophy in both the upper and lower body.
What is the main effect of creatine supplementation?
Increases PCr resynthesis
- This increases short-term, high-intensity exercise capacity to perform repeated bouts of high-intensity effort.
Describe the mechanism of action of creatine supplementation.
Its important in Phosphocreatine resynthesis. It increases levels of creatine in the muscle which means we can take a phosphate from ATP to add to creatine making phosphocreatine (via creatine kinase).
PCr levels are higher in which type of fiber?
type II fibers
When are PCR levels decreased? How long does it take for PCr to be depleted?
During maximal exercise (because its breakdown sustains high rates of ATP production) + 10seconds
How long does it take for 80% re-synthesis of PCr?
4 minutes
What are the benefits of creatine supplementation?
- Increased Cr stores 30% = Increased PCr resynthesis
- Increased muscle glycogen
- Increase growth factor expression
- Decreased muscle damage
- Training harder and longer = increase lean mass/strength
What are the best creatine sources?
- Diet - red meat (beef/pork) and fish (tuna, salmon, cod, herring)
- Creatine monohydrate (CM): white powder, 99% absorbed, better uptake mixed with a carb containing liquid or food, synthetic (suitable for vegetarians and vegans)
Describe a short, high-dose creatine loading protocol.
- 20g/day (split into 4 doses) for 5 days
- 0.3 g/kg BM (split into3-4 doses) for 5 days
Describe a long, low-dose creatine loading protocol.
3-5g/day for 20-30 days
How much would be a maintenance dose of creatine?
2-5g/day
Does creatine have an acute effect?
No - we need loading protocols
When is creatine supplementation most effective? Explain why.
When its co-ingested with carbohydrates or carbs + protein.
When you combine creatine supplementation with carbs, carbohydrates produce an insulin response which means creatine uptake into the muscle is more effective leading to greater phosphocreatine and creatine.
What is an issue with co-ingestion of creatine with carbs?
Massive amounts of carbs are required to maximize muscle creatine content.
Insulin response becomes hampered as time goes on so its more of a one off type protocol.
Using examples, when should we consider the use of creatine supplementation?
Single (+1-5%) and repeated bouts (+5-15%) of high-intensity exercise.
High-intensity max efforts <150 sec, largest effects on
<30 sec tasks.
Examples include;
- Power and strength sports: 100m, weightlifting
- Intermittent sports: hockey, football
- Resistance training aimed to incr. lean mass and muscular strength.
What has recent evidence shown on the effect of the combination of creatine and CHO loading during prolonged TT cycling?
it may increased power output during repeated high-intensity sprint efforts during the late stages of prolonged TT cycling
How can creatine supplementation reduce concussions?
Improvements in cognitive processing in the brain and potentially reduced damage and enhance recovery from mild traumatic brain injury/concussion.
What are individual variability considerations in creatine supplementation?
Baseline levels of muscle creatine
- Individuals with high muscle creatine levels will experience low creatine uptake from supplements.
- Individuals with low muscle creatine levels have the greatest potential for increases in response to supplementation.
Sport type
- In sports where performance isn’t determined by PCr availability (or fast ATP resynthesis) creatine supplementation will likely not have any effects (e.g. ultra-endurance or exclusively skill-based).
Why may there be an increase in body mass (1-2kg) when taking creatine?
likely as a result of water retention
How long would a washout period after using creatine be?
4-6 weeks
Are there any safety concerns with taking creatine? How can this be attenuated?
Mild, temporary gut upset can occur but can be attenuated with split dose, longer loading protocol and avoidance of high fibre foods with ingestion.
