caffeine

Question 1

what is caffeine?

Answer 1

1,3,7,-trimethylxanthine > metabolised in liver, commonly consume drug

Question 2

what is caffeines bio-availability?

Answer 2

interacts with all body cells and crosses the blood brain barrier peak blood caffeine concentrations occur 60 min after injection in dose-dependant way benefits from it occur soon after intake before rewashing peak blood concentrations

Question 3

what are the effects of caffeine?

Answer 3

• improved vigilance and alertness - reduced perception of effort - reduced fatigue and pain all = improved performance

Question 4

what is the key proposed mechanism to how caffeine works?

Answer 4

• central effect: adenosine binds to receptor causing fatigue. caffeine prevents adenosine binding delaying fatigue

Question 5

what are 2 other mechanisms for how caffeine works?

Answer 5

1. metabolic effect: stimulates lipolysis directly and via increase in adrenaline sparing muscle glycogen 2. muscle ion effect: caffeine stimulates calcium release which is important for muscle contraction

Question 6

further explain muscle ion effect mechanism?

Answer 6

• caffeine increases release of intramuscular calcium ions (responsible for muscle contractions) - happens in high doses - supplementation increase muscle force generation but this is not a consistent finding

Question 7

further explain metabolic effect?

Answer 7

• caffeine directly increases triglyceride breakdown out indirectly increases epinephrine stimulate fat metabolism - muscle glycogen sparing in certain conditions (high W, early in exercise)

Question 8

further explain central effect?

Answer 8

• caffein has similar chemical structure to a molecule called adenosine -caffein can stop it bing. to receptors in brain reduce tiredness and pain sensations

Question 9

content of caffeine

Answer 9

• varies across sources -coffee and tea are good sources but content is marked on preparation mode

Question 10

advantage of caffeinated gum

Answer 10

• bypasses the gut increasing absorption and decreasing GI distress

Question 11

optimal dose of caffeine for enhancing athletic performance?

Answer 11

• 3mg/kg BM -larger amounts don’t provide extra benefit and could increase side effects

Question 12

what to take for benefit?

Answer 12

• 40-60 mins before event/exercise - throughout at lower doses - late during or before important stage

Question 13

how does habituation affect intake?

Answer 13

• cyclist time trial (capsules of 6mg/kg) - not influence by level of habitual caffeine consumption - resulted in improved strength, endurance and jumping independently of caffeine consumption

Question 14

how does co-ingestion aid intake?

Answer 14

• caffein + CHO is ergogenic and consumed throughout time-trial - intake in energy drinks contribute to hydration goals - 70% improvement due to caffeine

Question 15

what should you consider using caffeine?

Answer 15

• endurance sports -brief sustained high-intensity sports -team/intermittent sports for work rates, skill and concentration -single efforts involving strength or power - pre-training energy boost if carrying fatigue into session

Question 16

what are the risks of caffeine?

Answer 16

1. sleep - interfere with recovery between training sessions. timing of intake relative to need for sleep should be considered 2. hydration - small moderate doses have minimal effects on overall hydration. caffeine constraining drinks contribute to fluid intake 3. moderate to high doses can cause anxiety, jitters, insomnia, less focus, GI unrest, irritability 4. withdrawal effects due to dependency

Question 17

what are the safety issues?

Answer 17

• excessive intake linked to health issues - can be lethal at high doses - use by children has greater risk and should limit intake to 2.5mg/kg/day - doping risk and athletes should only use batch tested supplements

Question 18

what are the key recommendations?

Answer 18

1. ergogenic effects of caffeine supported by scientific research 2. evidence caffein can enhance performance in range of different sports 3. high doses can cause negative side effects like gut upset, confusion, anxiety and disturbed sleep 4. generally safe to use but varies across individuals. consider dose, timing, product and event.