Development Team Member
Registered: 1380484167 Posts: 1,501
Sorry Ruud , but there is some more information on lactate and NIRS and why it can be used in combination and where or why it is much more questionable to be used in combination. But it is as well a respond to an increasing numbers of test I get mailed to me, where people use their lactate equipment and combine it with NIRS.
I will show some examples from contributor in this forum and some from outside contributor. It is very easy to understand why we hope or better hoped , that NIRS can give us lactate feedback. You can go back more than 10 years, where this was a common hope including for us but once we started to look at the both ideas we had to accept that they yes look at metabolic changes during an activity but in a very different easy. But one of the biggest fun part was, that we already had some discussion with lactate as the original idea, why we where testing for "lactic acid " was the bad reputation we forced upon this substance. So lactate is the reason for fatigue ,for failure for muscle soreness or what ever we got educated on.We have to avoid it have to learn to tolerate it and have to get rid of it as fast as possible. The problem was or is: In any lactate finger testing or ear, we have a value where we have more questions than actually a direction or answer. We have no clue on where it was produced, how much was produced, how much do we get in our sample, how much was recycled before the blood reached the finger, how fast does it disappear , what causes different speed of disappearance and so on. But the main reasons really was to find out the intensity , where we have a good option to go very long. let's name it aerobic or oxygenation intensity , so an intensity where e have no problem to create the ATP security by delivering steady O2 and in an amount, that we can nicely upkeep ATP levels, in fact we even can afford to do additional activities like talking as we have far enough O2 delivery that we can afford given out unused or nor delivered O2 deep enough into the lungs. Than we where hoping to find that nice balance so we where able to maintain performance as delivery and utilization of O2 was perfect and ATP levels ware save. And last but not least an intensity, where we feel or had the information, that we can not very long sustain, as O2 delivery was lower than the O2 needed for the activity including maintaining pO2 pressure in vital systems and keep ATP level in a needed level. The result of this mismatch of O2 delivery and O2 utilization than leads to a slow down of performance due to survival security for vital systems and ultimately ATP levels. The solution is relative simple. Get rid of O2 demanders or users , who are ultimately not needed for survival and that's where loco motor muscles come in and the often discussed metabolic pyramid. Now why this story. Main reason is a question I will answer on a different thread. But here first our dilemma. In the past we ad VO2 and lactate and not that easy for average daily users to have non stop feedback from this equipment. So we needed something and we developed test. Lab settings with specific guidelines but 85 % +- of the variables, the physiological systems where not that easy to control. Nevertheless we made big story out of room temperature, humidity, day time an much more as they for sure all influence physiological reactions. But we needed up with 1 point we search in a test like VO2 max . Max HR, LT 2 VT and so on. and form than on we where sure we had the gospel and where able to create calculated programs. There is or was another very important factor. Impression. If we tell people we will take blood and have gloves on and it looks very scientific , the test sells much better. If you add a mask and some bigger equipment with sound and graphs and you are even more impressed. How can we just fix a small device on a leg and arm yo barely see it you forget that it is there as you test and assume it is as accurad or close to as accurad as the other ideas we used.? Now this than leads to Zoning ideas, where when we go back in history started with the three explained above , but than we every new publication and to make a difference we started to add 4 5 and more zones into the idea. Than we used performance or HR as they are easy to use to believe, that we will be in the target zone when we use this feedback. We all know it can be true but as well we can be off. and HR is an example wattage users like to throw into the discussion. As much HR can be off due to different factors like heat, as one example so can be wattage off ( true still the same objective load, but very different physiological contributor or we may not even be able to reach this wattage ) out of the same reason in heat. Physiological change in survival mode so core temperature is the priority over performance and HR as a part of CO is needed to control the proper Core temperature and therefor less blood is available and with it O2 for the same performance we may had in a test a few days back. Where does that leads us. Well we need a direct live feedback and we can get rid of all this speculation as we see what is going on instead of speculating what may go on. This leads to some graphs for your own thinking. Above is NOT a 5/1/5 it is a three minute step test with stops of 1 min to take lactate so each lactate number is from a different load 250 watt start. So it is basically a classical step test with lactate to look for a lactate curve. Now blend out the NIRS data above and move back to the classical idea below Where is the LT ??. Now blend back and forget the LT here and think physiologically through each of the steps above and think what SmO2 trend may actually tell you. Noe below some lactate " curves" we have from 2 of Stuarts athletes. a. Sharon. ou can nicely see that the time we offer for her physiological systems change the trend in lactate by the same wattage ( wattage on the bottom axis) Y Now look again the live feedback with SmO2 trend and here to show it easier I use O2Hb in red. Can you see what mean with live feedback. If Sharon as a live feedback than she would not be thinking after the first 5 min with a lactate level of more than 1 mmol increase , that she reached her LT 2 ??? In fact she reaches another Lt 2 in the next step and again one in the lats step. More than 1 mmol increase form one step to the other ??? With a live feedback she had the nice information, that, yes she had to dig into her bank account initially or every time she starts new to maintain ATP levels but than she decided to get some supply to avoid a drop into a deficit. Physiological systems do not run into an O2 deficit and if they do the are dead.( Heart attack / Stroke to name some extreme situation , where O2 supply was stopped and we reached a deficit.) Below another lactate sampling from Stuart ( Allan ) Now imagine the SmO2 or O2Hb trend in this case ? And below as a repeat but to keep them together Sharon again with some questions. LT 2 where? FTP is above What do we do with all this confusion. Would it be not much easier to help Sharon with a love feedback for the goals we may set for her instead of hoping every day that one of the magical test results will actually be as well the proper physiological intensity on any common day.? Have fun thinking through this mess.