Supplements, caffeine and buffering agents (wk 10) Flashcards
What is 1,3, 7 trimethyl xanthine?
-> metabolised in the liver. Commonly consumed drug. Removed from WADA list in 2004 (previously 12 ug/mL limit). Sources: coffee, matcha, chocolate and energy/ caffeinated drinks e.g. red bull and coca cola.
What is the bioavailability of caffeine?
->P Peak blood caffeine concentrations typically occur ~60 min after ingestion in a dose-dependent way. However, benefits from caffeine can occur soon after intake (before reaching peak blood concentrations). Caffeine interacts with all body cells and crosses the blood-brain barrier. The half life is around ~5 hours.
What are the effects of caffeine?
-> improved vigilance and alertness, reduced perception of effort, reduced fatigue and pain, = improved performance (but has high individual variability)
Proposed mechanisms - Central effect: blocking adenosine:
. Central effect: blocking adenosine -> 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. It is the main mechanism.
Proposed mechanism: Metabolic effect - increase in fat mobilisation and oxidation:
- Metabolic effect: increase in fat mobilisation and oxidation -> Caffeine can directly (increased triglyceride breakdown) or indirectly (increased epinephrine) stimulate fat metabolism. Muscle glycogen sparing – only in certain conditions (9mg/kg, high W, early in exercise)
Proposed mechanisms: muscle ion effect - increase in 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. It was thought that caffeine supplementation might be able to increase muscle force generation, but this outcome is not consistent across studies.
What are the metabolic and Ca2+ mechanisms which contribute towards caffeine?
-Metabolic and Ca2+ mechanisms may contribute to the ergogenic effects of caffeine in specific exercise conditions (e.g. high doses), but the evidence is limited and not very convincing. Experimental evidence suggests that caffeine can improve performance in a wide variety of sports through its effects at several sites of the CNS, reducing fatigue and sensation of pain and improving alertness and reaction time, without the need of high doses.
What is the caffeine content?
- The content of caffeine varies across different sources, and it can vary within the same source
- Tea and coffee are good sources of caffeine, but the actual caffeine content can vary markedly depending on the preparation mode
- For exact caffeine content, supplements (batch tested) are recommended.
Describe caffeine sources:
-> Caffeine, delivered in any form, can improve various aspects of performance. An advent. age of using caffeinated gum is that most of the caffeine bypasses the gut (increased absorption, decreased GI distress)
Amount and timing of caffeine:
-Amount -> The optimal dose for enhancing athletic performance appears to be ~3mg/kg BM (same as the optimal dose for enhancing cognitive function). Larger amounts do not seem to provide an extra benefit and may increase side effects.
-Timing -> Usually ~40-60 min before the event or exercise. Through event at lower doses (~1.5 mg/kg). Late during the event, or before an important stage of the event (100-200mg)
What is co-ingestion, habituation and when to consider its use?
-Habituation -> Cycling time-trial performance effects of acute caffeine ingestion (capsules, 6mg/kg) were not influenced by the level of habitual caffeine consumption (low, moderate and high). Caffeine (capsules, 6mg/kg) supplementation resulted in improved strength endurance and jumping performance independently of habitual caffeine consumption (low, moderate and high).
-Co-ingestion -> Caffeine and CHO is ergogenic (consumed throughout a time trial). Caffeine taken in energy drinks can contribute to hydration goals. Co-ingestion with CHO is ergogenic and offers greater performance improvements than CHO alone.
-When to consider its use? -> Endurance sports (>60 min). Brief sustained high-intensity sports (1-60 min). Team and intermittent sports – work rates, skills and concentration. Single efforts involving strength or power. Pre-training energy boost if carrying fatigue into a session.
Draw the caffeine recommendations dependent on genetics:
What are the risks and other side effects of caffeine?
- Sleep – Caffeine can affect sleep onset and quality (even at low levels of intake), which may interfere with the athletes recovery between training sessions, or during multi-day competitions. The timing of caffeine intake relative to the need for sleep (half-life = ~5 hours) should be considered
- Hydration – Small to moderate doses of caffeine have minimal effects on urine losses or overall hydration in habitual caffeine users. In addition, caffeine-containing drinks such as tea, coffee and cola drinks contribute to fluid intake.
-Other side effects -> At moderate and high doses of caffeine (>6-9mg/kg) other side effects can occur: anxiety, jitters, insomnia, inability to focus, GI unrest and irritability. There is a dependency to caffeine – anxiety and sleep disorders, withdrawal effects can occur.
What are the safety issues?
-Caffeine is considered a safe compound for to athletes to consume, especially when low to moderate doses are ingested (around <400mg/day)
-Excessive caffeine intake has been linked with a number of health issues. Pure of highly concentrated caffeine can be potentially lethal and WADA continues to monitor patterns of misuse
-The use of caffeine by children carries greater risk, and children (<18 years) are suggested to limit caffeine intake to <2.5mg/kg/day
-All supplements have a doping risk of some kind. Some supplements are risker than others. Athletes should aim to only use batch-tested supplements
Background of buffering agents:
-> High rates of glycolysis during maximal intensity exercise leads to the accumulation of H+. Fall in intramuscular pH from ~7.1 to <6.5 (blood pH decreases from ~7.4 to 7.1). Acidosis inhibits glycolysis (PFK), reducing ATP production, causing fatigue. Various buffers minimise shift in pH.
What is beta-alanine?
-> Beta-alanine is a beta amino acid precursor of carnosine. Carnosine is a dipeptide made up of 2 amino acids beta-alanine and histidine. Carnosine is found in human skeletal muscle, which has an important role as intracellular pH buffer. Carnosine is found in red meat, chicken, fish and seafood.
What is beta-alanine in the diet and supplementation?
-> Although carnosine is found in red meat, poultry and fish, diet alone is not enough to increase muscle carnosine to levels required for a performance benefit. Beta-alanine supplementation is required for at least 4 weeks to achieve meaningful increases in muscle carnosine levels. Available in powder or tablet/ capsule forms. Slow-release capsules can help to improve retention, further increasing muscle carnosine levels. Carnosine requires chronic consumption (daily to actually have an affect)
What is the bioavailability of beta-alanine?
-> Is a relatively recent supplement. Those with 13g/day of carnosine had a greater affect on concentrations on carnosine in the muscle post-exercise, than a 3.2g/day and 5.2g/day of beta-alanine supplementation.
What is muscle carnosine content and the effect on performance?
-Muscle carnosine content -> Muscle carnosine content increased 60% after 4 week and 80% after 10 weeks.
-Effect on performance -> More carnosine over time, accumulates into improved performance
What are the mechanisms of action of beta-alanine?
-> Chronic beta-alanine supplementation increases muscle carnosine levels. Higher levels of muscle carnosine enhance intracellular buffering of H+ ions produced anaerobic glycolysis. Greater muscle buffering capacity can limit/ delay fatigue and improve exercise performance when exercise is limited by muscle acidosis.
What is the evidence for beta-alanine?
-> ‘Beta-alanine supplementation to improve exercise capacity and performance: a systematic review and meta-analysis’. Small yet significant performance benefits (~2-3%) during both continuous and intermittent high-intensity exercise tasks ranging from 30s to 10min in duration.
What is the supplementation regime of beta-alanine?
- Loading dose – 3.2g beta-alanine/ day for >8 weeks or 6.4g beta-alanine/ day for >4 weeks
- Maintenance dose – 1.2g beta-alanine/day
- Consume in split doses with meals – enhanced uptake and better management of side effects
When should you consider the use of beta-alanine?
- Short (30sec to 10min), sustained high-intensity sports e.g. rowing, trackm swimming, middle distance running
- In the weeks preceding a period of training where training intensity is prioritised, or before competition blocks
- Sports that involve repeated high-intensity efforts e.g. resistance training, team/field sports, racquet sports
What is the individual variability of beta-alanine?
-Individual variability -> The response between individuals can vary significantly:
* Baseline muscle carnosine levels: athletes who follow a plant-based diet may have lower levels of muscle carnosine, and therefore further room for improvement
* Training status: highly-trained individuals may experience smaller benefits from beta-alanine supplementation. However, this can still be worthwhile for athletes where small benefits can have a meaningful impact on sporting results.
