GREY curve shows a Lack of pyruvate. Below the threshold, so below the crossing point of the blue and red curve (from lactate graf), there is a gap between how much lactate could be combusted in the aerobic metabolism (fuel demand in the currency lactate), and how much lactate actually gets produced. As lactate gets transformed to pyruvate before it enters the aerobic metabolism, the difference between the lactate produced and the fuel needed can be named “the lack of pyruvate”. The lack of pyruvate becomes 0 at one intensity, and this is the intensity where the metabolism is saturated with lactate/pyruvate. This can be called the anaerobic threshold.
Imagine that the athlete accumulated a large amount of lactate during an effort, and he/she wants to get rid of it and exercises at a lower intensity. The upper ceiling of how much lactate can get consumed is still defined by the maximum aerobic lactate combustion (blue curve in lactate graph). But there is also a gross production – the red curve in the same graph. The gap between gross production and lactate combustion is the possibility to use additional lactate as fuel (the additional lactate that was accumulated in a hard effort). And this is what the grey curve named “lack of pyruvate” shows you. In practical applications, this means the ability of the athlete to recover as a function of speed or power. The curve is in mmol/l/min.
– the apex of the curve being at 1 mmol/l/min,
– the athlete accumulated an extra 8 mmol/l in the blood.
To fully recover from this and to get rid of the lactate, it would take him/her 8 / 1 = 8 min. If an athlete isn’t able to recover at the apex of the curve, but it is forced to ride at a much higher intensity, that means that the lack of pyruvate isn’t 1 mmol/l/min but only 0.5; the recovery time would be 8 / 0.5 = 16 min.
At higher intensity, lactate accumulates more and more, which can be seen in the PURPLE lactate accumulation curve. This shows the rate at which lactate accumulates (mmol/l per minute). Even though lactate is not directly responsible for muscle fatigue or loss of force, it is a valid marker for these sorts of feelings.
Therefore, the rate of lactate accumulation x the time of accumulation is highly associated with time to fatigue. Therefore, the lower the accumulation rate (= the purple curve is less steep), the better the athlete will perform riding above the threshold. Be aware that only the smallest differences in the grey and purple curves of lack of pyruvate and lactate accumulation can be extremely relevant to the performance in various sports.
For example, a cyclist benefits from slower fatigue riding above the threshold, and this is where the race is won.
– an athlete can reach a maximum of 10 mmol/l lactate above baseline,
– his threshold (crossing point) is at 375 watts,
– at an intensity of 400 watts his accumulation is 1 mmol/l/min.
This means he would be able to ride 10 / 1 = 10 min at 400 watts to reach his limit of 10 mmol/l of lactate.
If his accumulation at 400 watts is not 1 mmol/l/min but only 0.9 mmol/l/lmin. To reach his ceiling of 10 mmol/l/min, he can now ride 10 / 0.9 = 11 minutes 6 seconds at 400 watts. This is more than one minute longer, which can be absolutely decisive for a race.