Alkalisers and buffers Flashcards
During repeated sprints, why does our mean power output fall?
• An increase in metabolites • Glycogen depletion • PCr depletion • Muscle acidosis o Not lactate- H+ associated accumulation o pH <7 = acidosis
Give a simple overview of muscle contraction key steps
action potential –> neurotransmitter release –> Ca –> powerstroke/cross bridge formation
What molecule causes acidosis
protons
What can we do to lactate to prevent proton accumulation
Buffer it
H + Pyruvate –> ?
Lactate + H
HC03 + H –> ?
Co2 + H20
Give 3 ionic changes which occur extracellularly during fatigue
o ↓K o ↑Ca o ↑H o ↑Lactate o ↑Na o ↑Cl
Give 3 ionic changes which occur interstitially during fatigue
o ↓Na o ↓Cl o ↑K o ↑H o ↑Lactate
State 2 exchange channels the body has to alter ionic concentrations
- Na/H exchange channel
- H/lactate monocarboxylate
- Na/HCO3 transporter
- Na/K ATPase
Why are changes in K the most important ionic variation?
K is the key ion for the generation of action potentials
How many K in for Na out of the Na/K ATPase
2 K in
3 Na out
What is the resting membrane potential disturbed to during exercise
-70mv to -50mv.
Why is there a disturbance in resting membrane potential during exercise?
The Na/K pump is ATP dependent, and as during exercise ATP levels decrease, K+ rises extracellularly
True or False: The disturbance in resting membrane potential during exercise means a smaller change is required in MV to cause an action potential
True- This means there is a smaller force generation, which effects Ca2+ release.
What process may attenuate K increase, preventing the change in H ions
Alkalosis
HCO3 is an extracellular buffer. How does it work?
It decreases H and therefore K but doesn’t change blood lactate
Why is buffering beneficial
allows the body to work harder i.e. generate more lactate for longer
but without the performance decrements normally associated with increased lactate.
Give an example of an alkaliser
- sodium bicarbonate
- sodium citrate
How do alkalisers work?
increases blood HCO3 pool, and therefore the muscle.
They can increase time to exhaustion.
What type of events may alkalisers be beneficial for
They are useful for anaerobic glycolysis events, or those effected by a reduced pH.
True or False: alkalisers cause an increase in H
True, but though more H were produced (increased Bla),
NaHCO3 and NaCitrate buffered it with HCO3 so effects weren’t felt
What is a beneficial effect of chronic bicarbonate supplementation?
pH reduced and there was an increased buffering ability and power seen, with high supplementation for 5 days prior
Describe alkalisers effectiveness as a training aid
There is a ceiling effect- increased buffering in untrained athletes
Increases VO2 max
Increases lactate threshold
Increase exercise at pre-training VO2max
Increase exercise duration
Increases stress on body, so greater adaptions seen
Give 2 side effects of alkalisers
- Vomiting
- Diarrhoea
- Dizziness
- GI distress
What is the optimum timing for alkaliser supplementation
• 120-150 mins prior to exercise
o Or 60 mins prior if in capsule form
What should alkalisers be co-ingested with
a light meal or fluid such as orange juice
What is the optimum dose of alkalisers
0.3-0.5g/kg/BW of bicarbonate
Give 2 examples of intracellular buffers
PCr, Protein, Carnosine or Bicarbonate
What is carnosine
A dipeptide found in animal flesh, made up of L-Histidine and Beta-Alanine
How does carnosine work
It acts as a buffer, antioxidant and prevents glycosylation or carbonylation.
The N group removes H+ after exercise, decreasing H+ accumulation.
Which muscle fibre type has the greatest amount of carnosine in
Type II
Describe the synthesis of carnosine in the body
Carnosine (from diet) –> histidine and B-alanine (in blood) –> carnosine (in skeletal muscle)
What does B alanine share a transporter with
taurine
What are the benefits of B alanine
decreases neuromuscular fatigue, improves ca handling, and increases exercise duration
What is the wash out period of carnosine
16-20 weeks
What is the wash out period for PCr and Cr
4 weeks
Give 2 side effects of carnosine
• Paraesthesia • Hypertension • Double vision • Weight gain • Because uses same transporter as taurine o May be decreased performance o Effects mood
What type of exercise may B alanine be beneficial for
exercise >60 secs
