Caffeine W10 Flashcards
Where is caffeine metabolised?
The liver
What is caffeine?
1,3,7-trimthylxanthine
When do peak blood caffeine concentration occur?
Typically occurs 60min after ingestion in a dose-dependent way
What are the effects of caffeine?
Improved vigilance and alertness
Reduced perception of effort
Reduced fatigue and pain
What is the number 1 mechanism of caffeine? (Central Effect)
When adenosine binds to its receptor, this causes fatigue. Caffeine prevents adenosine binding and thereby delays fatigue
What is the number 2 mechanism of caffeine? (Metabolic effect)
Caffeine stimulates lipolysis (breakdown of triglycerides), directly and via an increase in adrenaline. This may spare muscle glycogen
What is the number 3 mechanism of caffeine? (Muscle ion effect)
Caffeine stimulates calcium release which is important for muscle contraction
How does caffeine increase calcium release in muscle?
Caffeine increases the release of intramuscular calcium ions (Ca2+), responsible for muscle contractions, although this seems to happen with very high doses of caffeine
How does caffeine increase fat metabolism and oxidation?
Caffeine can directly (increase triglycerides breakdown) or indirectly (increase epinephrine)
Does caffeine and carbohydrate co-ingestion work in influencing substrate metabolism?
No- there is no effect on substrate metabolism
How does caffeine block adenosine?
The MAIN MECHANISM
Caffeine has similar chemical structure to a molecule called adenosine (responsible for feelings of tiredness, fatigue and even pain sensation)
Therefore, caffeine can stop adenosine from binding to its receptors in the brain, reducing the sensations of both tiredness and pain
What is an advantage of using caffeinated gum?
Most of the caffeine bypasses the gut
- increases absorption
- decreases GI distress
What is the optimal dose of caffeine to enhance athletic performance?
3mg/kg BM
When should you consume caffeine to enhance performance?
40-60min prior
How much caffeine should you ingest doing exercise?
1.5mg/kg
How much caffeine should you ingest during late stages or important stages of exercise?
100-200mg
What is co-ingestion with CHO like?
Ergogenic
When should you consider caffeine usage?
Endurance sports (>60mins)
Brief sustained high-intensity sports (1-60min)
Team and intermittent sports- work rates, skills and concentrations
Single efforts involving strength or power
Pre-training energy boost if carrying fatigue into a session
How can caffeine influence hydration?
Small to moderate doses of caffeine have minimal effects on urine losses or overall hydration in habitual caffeine users
What are the side effects of caffeine?
At moderate and high doses of caffeine (>6-9mg/kg) other side effects can occur
- Jitters
- Insomnia
- Inability to focus
- GI unrest
- Irritability
There is a dependency to caffeine- anxiety and sleep disorders, withdrawal effects can occur
What are the recommendations for caffeine?
The ergogenic effects of caffeine are supported by scientific research, and it is not in WADA’s prohibit list
There is evidence that caffeine (3mg/kg BM) can enhance performance in a range of different sports
High doses can cause negative side effects including gut upset, confusion, anxiety and disturbed sleep (time!)
Generally safe to use, although it varies across individuals. Practical considerations: dose, timing, product, event
What is the half-life of caffeine?
4-6hours
Why is there no effect on substrate level metabolism when caffeine is consumed ?
Due to insulin being more prominent and stronger effector when consumed with carbohydrate
May have an effect in a fasted state
When does caffeine habitual consumption affect ergogenic effects?
6mg/kg BM
How much caffeine should children <18 limit to?
<2.5mg/kg/day
What is a safe dose of caffeine to ingest?
400mg/day from all sources and 200mg at any one time
