Lower VO2 Max

I used to think that VO2Max was something useful, but it isn't. And it's not that Garmin is doing something wrong. Take a look at these highlights from this scientific study:

"CGM (Central Governor Model) predicts that the body regulates exercise to prevent myocardial ischemia during exercise. This is accomplished by limiting the blood flow to the periphery which the brain accomplishes by regulating muscle recruitment. Therefore, VO2max reflects this regulation of muscles recruitment. In essence, a central governor acts as a regulator for exercise instead of exercise being limited by some parameter.

A runner tested running versus another modality such as cycling will have different VO2max values. There is great individual variation too, between 0 and 13% in the aforementioned study.

After 4 weeks of training using an interval program designed to elicit time at VO2max, VO2max and, more importantly, performance did not improve. In addition, even in untrained people, the [study] stated that improvements in VO2max at high intensities were not dependent on the volume of training.

The study showed that while on average improvements were seen in a variety of endurance parameters after six weeks of endurance training, the individuality of the response was widespread with some showing even negative responses to the training.

The change in VO2max did not correlate with the change in performance on a time trial. Studies demonstrate improved performances without changes in VO2max. In a study on a female Olympic level runner, Jones showed that while the athlete’s 3,000m time improved by 46 seconds, there VO2max decreased from 72 ml/kg/min down to 66 ml/kg/min.

The fact that Radcliffe’s VO2max was essentially stable despite her training volume and intensity increasing substantially is intriguing. Her training increased from a modest 25-30 miles per week (and her VO2max was already 72 at the time) to 120-160 miles per week.

In untrained subjects VO2max increased during the first 4 weeks of training, but did not increase after that even with a further increase of training, despite continued improvements in performance.

There recognition that aerobic performance and VO2max are not direct equals or even well linked is a step in the right direction and needs to be acknowledged to a much greater degree."

Source: https://www.scienceofrunning.com/2009/12/fallacy-of-vo2max-and-vo2max.html?v=47e5dceea252

In answer to your question, here is the science behind how the number is recorded. 

discover.garmin.com/.../

The first sentence of this Garmin article sums up everything that is written there, but it's not science, just marketing: 'VO2 max is the defining measure of cardiorespiratory fitness and aerobic performance capacity'. No, VO2Max doesn't measure fitness, and seeing this number changing doesn't mean anything. Science is not a short text written by a company with no references to other studies, no peer-review, no proof of anything. It's just ***.