Lecture 7 (1) - Sodium bicarbonate and caffeine Flashcards
Sodium bicarbonate (SB)
- SB (NaHC03) is a salt composed of sodium ions and bicarbonate ions
- It is an alkalinising agent, also referred to as baking soda
why take SB?
During intense exercise the H+ build up exceeds the bodies capacity to excrete the H+ from the blood. Here we require exogenous support.
- Consuming exogenous bicarbonate can help to buffer H+ from the blood (not muscle but efflux of H+ from blood has the knock-on effect of increasing efflux from the muscle to the blood).
- SB is a blood buffer – buffers H+ from the blood. Reduces acidity to ensure we can keep exercising at the intensity that we want
Does SB work?
- pH levels massively drop after exercise. However, when SB has been consumed prior to exercise, the drop in pH is reduced (attenuates the decline). Sodium bicarb ingestion does help reduce blood pH- alkalising the blood before exercise
- Looked at SB vs sodium and change in sprint performance. Looked at change in peak power. Improvements shown for repeated sprint exercise – increases in peak power output
Meta-analysis of Sodium Bicarbonate use for athletic performance:
- Small but meaningful benefits might be achieved with sodium bicarbonate ingestion
- Better for events >1-7minutes
- Effects quite indiviudal – might not be useful for all elite athletes
- Best dose is 0.2-0.4 g/kg body mass, 60-120mins pre-exercise in flavoured water or capsules
Meta-analysis - Effects of SB on muscle strength and endurance:
- Found no effect on muscle strength (no improvement in maximum strength as this uses the PC system)
- Improvements in muscular endurance (25-30 reps – 45-60seconds of work)
Sodium citrate:
- Sodium citrate is also an alkalinising agent, and works in a similar fashion to SB
- Proposed to provide the same benefits as SB without the GI distress (however this is not well supported in research)
who would benefit from SB/ SC
- Anything over 25mins is unlikely to benefit. SB will not benefit football, rugby
- Good for lower intensity higher duration e.g., 5K
- Good for 2,000m row
Good for intermittent sprint performance in a training session
Side effects of SB
- Gastro-intestinal complaints are common
Caffeine
- Caffeine is a stimulant of the central nervous system – found in many plants (natural)
- Can increase alertness and delay the onset of fatigue, most notably blocks the adenosine receptor
- Was banned for use by WADA until 2024
- Caffeine gel, caffeine boost shots, caffeine energy bars, caffeine gums
Health Canada and the FDA recommend drinking no more than 400mg of caffeine a day
- The average cup of coffee (8oz) has just over 100mg of caffeine
How does caffeine work?
- First work in the 1970s found that caffeine increased fatty acid oxidation during aerobic exercise. During exercise you burn more fat when consumed caffeine compared to glucose and a control. Boosted FA oxidation results in less reliance on glycogen – keep going for longer
- Several later studies found performance improvements without changes in fat oxidation, indicating that this was not the key mechanism for the performance effects
Other mechanisms involved in caffeine supplementation
- Precise mechanisms not clear, but likely related to caffeine as a stimulant – exercise feels easier when caffeine is consumed
- Most hypothesises are related to its ability to decrease RPE and the direct act of the adenosine receptors to increase arousal. Perception of effort is decreased after caffeine consumption. Adenosine is a neurotransmitter which binds to receptor to create a change.
- Caffeine is an antagonist at the receptor so blocks adenosine binding. When adenosine binds it promotes sleep. Therefore, blocking the binding, will prevent lethargy and fatigue.
- Caffeine might also increase Ca2+ release from the sarcoplasmic reticulum helping to enhance muscle force production – this could translate into greater power output and performance in resistance and aerobic exercise
- Enhance force production through calcium mediated effect.
Recommended caffeine dosage:
3 mg/kg
5, 9, 13 mg/kg all improved performance to same extent - plateau effect (more is not better)
Effective of caffeine chewing gum on race performance:
- Twenty competitive cyclists completed two 30-km time trials that included a maximal effort 0.2-km sprint each 10-km.
- Caffeine (~3–4 mg/kg) or placebo was administered double-blind via chewing gum at the 10-km point following completion of the first sprint
- Found that HR was higher after caffeine, lactate was higher, mean power higher, sprint power higher, time was shorter
Often high individual variability occurs in caffeine trials
Wake up and smell the coffee: caffeine supplementation and exercise performance meta-analysis of 21 meta-analysis (umbrella review):
- Overall conclusion that effects of caffeine are better with aerobic exercise as opposed to anaerobic exercise
- For aerobic exercise, caffeine is beneficial for performance
Side effects of caffeine:
Caffeine shakes, irritability, disrupted sleep, GI function, tremor, bradycardia
There is limited evidence to suggest that caffeine is a diuretic
