[Scott Johnston]

Balfer:

Sorry to be so slow responding. I thought I responded, but it looks like my reply didn’t post.  So here goes:

First, do not rely on your AW to give you any meaningful estimate of your VO2max.  Besides, what you are exercising for is to improve your aerobic performance, not to move a needle on a measurement that is a proxy for performance.

Your early lactate numbers are not outrageous, but they do indicate someone with what we call aerobic deficiency. While it could be related to metabolic efficiency at 130-135, another contributing factor for the lactate dropping after 90 minutes is that you began to deplete muscle and liver glycogen stores, and your metabolism was forced to switch to more fat for fuel.   Muscle glycogen depletion is one of the most powerful signals to your genes to make beneficial aerobic adaptations.

I would recommend you do a HR drift test as described here.

We have used that test to establish the upper limit of zone 2 with literally thousands of athletes, and it correlates very well with lab gas exchange tests.

As for what to do next:

Do the HR drift test to set the top of Z2.  Do all your endurance training below that HR value.  Drop the VO2 max workouts. They are slowing your aerobic adaptation.  High-intensity training with a large accumulation of lactate and the concomitant hydrogen ions H+ down-regulates the gene expression for the aerobic adaptations you are looking for.  There is a time and place for high-intensity training, and it does have a beneficial effect on cardiac stroke volume, but your limitation is peripheral (muscular metabolism), not central (cardiac output), and you need to focus on the low-hanging fruit. You might want to read this article .

If you choose not to do that, I would continue what you are doing.  If it ain’t broke, don’t fix it.  But the way you know your training is working is by measuring performance, not a performance metric.  Do a time trial at 115 or what ever HR you choose. Train using that upper limit and repeat the time trial in 4 weeks.  That is usually long enough to see measurable progress.

You may also find this book a useful resource.

I hope this helps.
Scott