Science with STAPS – we explain things!
Individual anaerobic threshold, aerobic threshold, 4 mmol threshold and so on ... There probably are many more terms to describe this “mysterious“ threshold so many pieces have been written and lectures been held on. Instead of wasting time defining a name for this threshold, we would rather like to explain what it is all about:
The anaerobic threshold (as we call it) is not the transition from aerobic to anaerobic metabolism. And the allegedly occurring acidification is not the reason for the break-off when riding / running at the anaerobic threshold, either.
The anaerobic threshold determines the highest performance / intensity possible at which physiologically there still is a steady state of lactate. In other words: lactate production (via the anaerobic metabolism) is exactly as high as lactate oxidation (via the aerobic metabolism). Unlike the linearly proceeding lactate oxidation, the lactate production is an exponential process (see picture), therefore both metabolic pathways intersect at a certain intensity. As soon as this intensity is surpassed and by climbs above the anaerobic threshold, the athlete produces more lactate than he or she can break down – with the consequence of acidification.
Clearing up the (wrong!) myths surrounding the anaerobic threshold:
- the anaerobic threshold is not the transition from aerobic to anaerobic metabolism, but the maximum steady state of lactate, i.e. both metabolic pathways run “equal“, the resulting lactate concentration remains the same!
- lactate production does not start at the anaerobic threshold only: lactate is always produced (with or without training load!) and further metabolized!
- acidification is no break-off criterion: where is acidification to stem from when riding at the anaerobic threshold, if lactate production and lactate break down are at equilibrium?!
- the limitation of stress duration at the anaerobic threshold is of an almost exclusively energetic nature: the consumption of carbohydrates is so high that it cannot be topped up adequately!