All text and images from Alan Couzens.
The #AerobicThreshold or first rise in the lactate curve is a key training intensity.
Primarily because it usually coincides with the highest rates of #FatBurning coupled with relatively low CHO oxidation, so the athlete can accrue a lot of work with minimal metabolic fatigue.
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| VE = ventillatory efficiency, or how deeply you breathe. RR = respiration rate. |
As the chart above shows, when an athlete begins a progressive metabolic test their VO2 (oxygen) requirements increase almost immediately & in fairly direct proportion to the exercise intensity. It makes sense then that we'd have to increase our breathing to match this, right?
Wrong!
Our body is pretty wasteful with O2 at rest. Our muscles don't take up most of the O2 in the blood & it just cycles around. Therefore, the first port of call when our body needs more O2 is simply for the muscles to take up more already circulating O2 from the blood...
This shows up as an increase in the a-VO2 difference, i.e. the *arterio* *venous* *oxygen* *difference* - the difference between the amount of O2 in the blood of our arteries going into the muscle & our veins coming out...
https://twitter.com/alan_couzens/status/1488891134466084864?s=21&t=GfrF4HO0hBGxSZfFjVoy8g
As we continue to increase the intensity of exercise after moving from nose breathing to quiet mouth breathing, eventually we encounter a second breakpoint in ventilation - the transition from quiet mouth breathing to loud mouth breathing...
At this point, metabolic acidosis is starting to increase and the body's response to it is to "blow off" the increasing carbonic acid in the form of additional CO2...
This is directly visible in the relationship between VCO2 (the amount of carbon dioxide being produced) vs VO2 (the amount of Oxygen being consumed). At this point in the test the CO2 line takes a turn & begins approaching the O2 line.
https://twitter.com/alan_couzens/status/1489260556934471681?s=21&t=GfrF4HO0hBGxSZfFjVoy8g
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