lower pH decreases O2 saturation

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16 years ago 10/12/2007 12:45pm EDT

I think its fairly accpeted that a decrease in blood pH has the resulting effect in decreasing hemoglobins affinite for O2 and therefore lowering it saturation.

My query is on how this might effect middle distance races in athletes with the same speed at LT but at different lactate concentrations. (ie athlete A might have a lactate contentration of 4mmol/L at LT/MLSS (whatever your preferble term is...) whereas athlete B might have a lactate of 6mmol/L at LT/MLSS, although they both have the same speed at LT/MLSS. I haven't worded that very well but i hope you get the jist.

Athlete A should have a higher O2 saturation than athlete B at any given speed (where lacatte is produced and blood pH drops) as they have a pH closer to normal but does any body have ideas on how this might effect them during a race?

16 years ago 10/12/2007 1:42pm EDT

re: Physiologist1979

if lower ph decreases hemoglobins which main function is to carry oxygen aka energy to the bodies tissues. how do you think that would affect you?

16 years ago 10/13/2007 9:42am EDT

re: Physiologist1979

For those two hypothetical runners, runner A has better endurance obviously, but runner B might have better sprinting speed.

Runner A might be faster in a 1500m race, runner B, faster in a 400m race, where he is less troubled by lower blood pH/higher H+ concentration.

16 years ago 10/13/2007 1:54pm EDT

re: Physiologist1979

This drop in pH would facilitate the unloading of O2 in the active muscle, thus augmenting VO2. That's a good thing.

And technically, the MLSS is not a true steady state.

http://www.cellml.org/models/dash_bassingthwaighte_2004_version01

To answer your question:

It wouldn't matter at all as runner B also has the greater capacity to move further from equilibrium. Basically, various combinations of oxidative and oxygen independent energy capability could allow an identical performance velocity.

In a real middle distance race however, the higher end lactate value would be a predictor of racing success, not failure.

16 years ago 10/13/2007 4:17pm EDT

re: Physiologist1979

"fairly accepted"? I believe that is Bohr's Law.

The increase in acidity (lowered pH) is a good thing as it allows more O2 to be released from the hemoglobin when the RBC reaches the muscle (an area of low O2 pressure during exercise).

16 years ago 10/13/2007 5:17pm EDT

re: luv2run

luv2run wrote:
"fairly accepted"? I believe that is Bohr's Law.
The increase in acidity (lowered pH) is a good thing as it allows more O2 to be released from the hemoglobin when the RBC reaches the muscle (an area of low O2 pressure during exercise).

You're kidding? Blood pH is one of the most tightly regulated aspects of human physiology, resting in a narrow range of 7.35-7.45. One might see a blood pH of 7.2 during intense exercise, but anything lower (7.0) would result in acidosis, and a severe metabolic crisis, which could ultimately lead in anaphylactic shock or death.

I think you guys are referring to interstitial pH aren't you?

16 years ago 10/13/2007 5:32pm EDT

re: Physiologist1979

The difference in blood lactate levels could be due to a number of factors, most importantly running economy

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