Posted by Cris LaBossiere (24.66.94.141) on January 22, 2004 at 08:58:39:
Juerg is on to something with ammonia and urea sampling along with lactate. In terms of measuring muscle metabolism we only have indirect measurements available. Heart rate is thought to increase exponentially after the lactate threshold, I agree with this. So we use heart rate to measure aerobic/ anaerobic state indirectly, but not very well.
Then lactate came along (portable) and now we measure directly what heart rate did indirectly… well almost.. As Juerg points out our fingertip is a long way from our leg muscles. We measure blood lactate, and not muscle acidity. Blood lactate is a better indication of muscle acidity than heart rate, but blood lactate is still indirect.
We are like astronomers trying to measure a planet we can’t see. But because light bends a certain way, and because the orbit of other objects nearby is effected a certain way, astronomers decide these effects can only happen because something must be there. The astronomers without seeing something will say, “we know something is there because we have measured it’s affects on other things nearby.
Right now we measure how muscles affect things nearby (blood lactate, heart rate, ammonia, urea, testosterone, cortisol, etc.).
If we try to find our way through a city and we can only see to the front and not the side, we can only react after we see what is in front of us, we can’t have a good reason to turn left or right because we can’t see to the side, so each way we turn is a blind guess. When we add the ability to see to the side, we can see a short distance down the side streets before we turn, so now we have a better idea of where to go, but we still don’t know what is around the next corner.
When we add the “birds eye view” everything changes, now we see the whole city at once with all the streets, pathways, buildings, systems etc. This makes navigation instant. But we still don’t know what is inside buildings until we go inside.
At this stage in measuring training we can look forward, backward, and a little to the sides. It will be many years before we have the birds eye view and longer still before we see inside everything.
Lactate is very important right now, because we don’t have much else in terms of measuring metabolic pathways. But when we use lactate with heart rate and wattage, our combined tools let us see much more than only one tool at a time.
The lactate paradox problems that Juerg is discussing are very important. If we can be as smart as the astronomers, we may be able to make some conclusions without seeing the thing we are talking about.
I agree that the PC adaptation is a metabolic adaptation problem in the hip flexor muscles. I also agree that the reason why blood lactate doesn’t show this very well, (at least not in the way we expect) is because the hip flexors don’t dump a large enough volume of lactate into the blood to make a big difference, even though the hip flexors are largely anaerobic in the early “untrained state” of first time on PC.
A study done on rock climbers in England made a similar conclusion when they tested blood lactate at the time of forearm muscle fatigue/ failure. Blood lactate was well below “4.0”, yet the subjects forearms were “burning” and became fatigued. The total mass of the relatively small forearm muscles was not enough to fill the blood with lactate like the comparatively enormous leg muscles can.
So “blood lactate” does not always match an exact corresponding muscle ph. We need to understand that most of our standard blood lactate concentration conclusions regarding aerobic/ anaerobic shift are made through measuring leg dominant exercises like running and cycling. These two are chosen for research because they are the most popular exercise machines in laboratories, and further the bicycle is chosen because the variable of an individuals mass is mitigated by the seated position, and the bike is better for safety (falling off a treadmill hurts).
So another good point by Juerg that heart rate values may be different in the field than in the lab, even if the same power is developed. It’s a good thing we have heart rate monitors and portable lactate analyzers so we can measure what happens in the real world and not just the lab.
We should also be prepared to expect different blood lactate correlations to aerobic/ anaerobic shift with smaller and larger muscle mass recruitment because the size of the muscle influences the total volume of lactate per unit of time dumped into the blood stream. Smaller quantities of lactate may be taken up by surrounding muscle, the heart, and the liver, before blood concentration increases in the way we have come to expect.
For now we “triangulate” so to speak, our position for making up our minds in training decisions by using 3 or more specific simultaneous factors, the main three being; heart rate, blood lactate, and speed/ wattage. We also use blood glucose, ammonia, urea, and in the future some kind of metabolic scanner. Lets always be ready to move beyond blood lactate and heart rate as the main measurements, but for now these are the two big biological measurements that we compare to speed/ power.