Negative Anaerobic reserve
Is it possible to have a negative anaerobic reserve? Definitely NO. We can not draw more electricity from a battery than its total charge and we can not pour more than 33 cl of water from a 33 cl glass.
However the calculation of the anaerobic reserve or balance W’bal may yield negative values for a number of reasons.
Statistical variations. The anaerobic capacity W’ is obtained from the ECP model and from fitting of the reference power test values. This W’ number is subject to statistical uncertainty of at least 5 % which means that any computed W’bal that lies within 5% of zero value is to be considered as zero. A W’bal of -5% is still to be considered as normal, and approximately zero.
Inacurate reference data. In our ECP model we use a set of 5 reference data or Exhaustive-Power-Duration data. Each off these 5 data pairs are obtained from dedicated test rides untill exhaustion, i.e. P2, P5, P10, P20, P40. All other systems use sloppy data based on “best performances”, alternatively called P-D curves, Power Profile, MMP, CP-curve etc…These data do not necessarily present rides til exhaustion and are not suitable for any Critical Power model calculation. Using unfiltered MMP curve data will necessarily lead to multiple and very deep negative W’bal values.
Wrong models. Any correct ExRec (Exhaustion-Recovery) model should code correctly for the rate of loss of anaerobic reserve at any given power level P and for the rate of recovery when power is below the recovery threshold RT. Wrong models give wrong results.
A genuine negative W’ bal value occurs when the rider eventually outperforms or sets a new all-out record. Having a superday or having “good legs” may indeed yield a negative anaerobic balance. In this case the detected performance may be used to update the reference data. Also, when a higher value is detected for e.g. 10 minutes it is advisable to perform also new tests on the other values P5 and P2
This picture shows the result of a 10-minute all-out test leading to a -20 % negative anaerobic reserve. Prior to this test the registered reference value was P10 = 427 Watt. The riders ECP values are RT = 319W, CP = MAP = 395 W, SCP = 426 W and W’ = 21499 kJ. The test was included into a longer field training. The new average power on 10 minutes is P10 = 434 Watt i.e. only 1.6 % higher than the older value. To be clear, in this 10-minutes performance a 20% variation of anaerobic capacity corresponds to only a 1.6 % variation in total average power.