Case Study: Two Examples of Client Exercise Testing with VO2 Master

Written by: Philip Batterson, Ph.D., Integrative Physiologist and Endurance Coach

While graded exercise tests (GXTs) are typically used to determine maximal oxygen consumption (VO2 max), they can provide more actionable information than just VO2 max data.

A proper GXT can determine your clients’ VO2 max and where their physiology changes in response to different exercise intensities, allowing you to determine their individual training zones.

Whether you train performance-oriented individuals or those who just want to improve their health and wellness, GXTs are useful tools for helping anyone individualize their training to maximize their adaptations. 

In this blog post, I will walk through two of my clients’ training regimens to explain how I use a GXT to determine zones. I also share effective training recommendations for individuals’ wellness and performance. 

How to use graded exercise testing for individuals focusing on athletic performance

The first athlete came to me with the goal of increasing his biking capacity for a road cycling race that was expected to be around a one-hour finishing time.

He had a significant background in training (over four years) but was limited on time (family, job, etc.). He wanted to make sure he was training in the best zones to help target the proper physiological adaptations and avoid overdoing his training. 

We created a graded exercise test based on his current fitness level. His expected power output for 40 minutes was around 250 watts. So, I tailored the graded exercise test to hit 250w about 7 minutes into the test. We increased power output by  20 watts every minute so that the test would be completed in between 7 to 15 minutes. 

It’s important to determine a measure that is close to your clients’ threshold power or speed. This measure should be maintainable for 30 minutes but not longer than 60 minutes—it could be anything from a 10k time to functional threshold power. Having an estimate of this number gives you a good starting point for where the intensity should be seven to eight minutes into the graded exercise test. 

We monitored heart rate, power output, and gas exchange/respiratory variables with the VO2 Master and Polar heart rate monitor during the test.

We also weighed him on a good-quality scale before the test, as weight is an important part of the relative VO2 calculation.

Upon completion of the test, the first things I looked at were:

1. What was the athlete’s VO2 max?
2. How does his VO2 max compare to other athletes in his demographic?
3. Is his VO2 max adequately high for his performance goals?
4. Was his VO2 max potentially limiting his performance? 
5. Where were his first and second ventilatory thresholds occurring, and how close were they?

The first ventilatory threshold (VT1) is where breathing, measured by minute ventilation Ve (l/min), starts to increase from normal baseline levels. VT1 indicates the point where more CO2 is being created due to muscle metabolism shifting from fat oxidation to carbohydrates. 

The second ventilatory threshold (VT2) is where breathing increases again. VT2 indicates the point where our bodies become more reliant on anaerobic energy systems and have to start creating even more CO2 to buffer H+ molecules coming from contraction. 

Let’s look at his test report.

His VO2 max was (51 ml/kg/min) at a maximal power of 360w, which is higher than 93% of males, 40-45 years old.

Based on this data, I concluded that his VO2 max was likely high enough for the individuals he was going to race against. 

Next, I looked at where his first and second thresholds were occurring. Most importantly, I determined where his second threshold was—in his race, he will have to be very close to his second threshold but not over it. His first thresholds occurred at 138 watts and 145 bpm. His second threshold occurred at 304 watts and 165 bpm. 

Looking at elite athletes shows us that second thresholds can occur up to approximately 93% of VO2 max. Most individuals have a second threshold between 70 and 85% depending on training status and specific work. 

His second threshold was around 97% of his maximal heart rate! 

At first glance it appeared that VO2 max was not limiting his performance. However, after looking at where his second threshold was in relation to his VO2 max, I realized there was a potential that his VO2 max was limiting his ability to raise his second threshold, which, as stated above, is very important for races between 45 and 90 minutes.

Training Recommendations 

Since he was working on completing a one-hour race, I recommended three to five days a week of training in zone 2 between 125-145w and 130-152 bpm. This recommendation will build volume but limit the amount of accumulated fatigue. 

For his specific higher-intensity work one to two days per week, I recommended accumulating time near or above VO2 max power (320-360+w) to help improve his VO2 max. We aimed to complete this style of training, progressively increasing intensity for five to eight weeks. Then, we tested again with the expectation that his VO2 max would improve. If it did improve, we would then work together on raising his second threshold and completing more specific work leading into his race.

How to use graded exercise testing for individuals focusing on wellness

The second client came to me after reading the new Peter Attia book. This client’s goals were to determine her zone 2 intensity and measure her VO2 max so she could track her cardiovascular fitness and get proper pacing strategies for health and longevity.

VO2 max has been shown to be a predictor of all-cause mortality—the higher your VO2 max is, the lower the risk of cardiovascular events and dying from other causes. 

Zone 2 work is an effective means of improving fat oxidation and blood markers in overweight obese individuals. It’s also an effective way of accumulating training volume, which is associated with improvements in metabolic health.

This individual did not have much experience with training. She lived a mostly sedentary lifestyle but was otherwise healthy. She told me she loved walking and occasionally biking outside. Since she had done very minimal activity lately, I had her complete her graded exercise test on a stationary bike, mainly for safety but also because it does not seem to make a difference if untrained individuals complete a treadmill or bike protocol. 

It was tough to know what this individual’s capabilities for maximal exercise would be, so I had her do a standard protocol that I had used with sedentary females in the past. 

She started at 60 watts, and we increased power by 20 watts per minute until she couldn’t maintain a cadence of 55 rpms.

During the test, we monitored heart rate, power output, and gas exchange/respiratory variables (with the VO2 Master).

Upon completion of the test, the primary variables of interest were:

1. VO2 max and how it compared to others in her demographics.
2. Her training zones so we could dial in specific training intensities, especially for zone 2 exercise.

Let’s look at her test report.

From the data, we see that her VO2 max was (37.5 ml/kg/min) at a maximal power of 180 watts, which was higher than 58% of females aged 35-39 years old. This is fairly good, but there is some room for improvement. 

Training Recommendations 

Since her main goal was to train for health and wellness, I recommended zone 2 training three to five days a week, 30 to 60 minutes a day for four weeks. I also recommended her zone 2 training intensity should stay between 126 and 147 bpm. I told her this could be done by walking, jogging, or cycling since those were the exercises she indicated would be most enjoyable. 

As she hadn’t been doing any training, I started her with three days per week, 30 minutes per day, and worked her up to four to five days per week. 

I didn’t have her do any high-intensity training for the first four weeks. Then, for the next six weeks, I had her introduce some VO2 max work into her training. She did 10 reps with 1 minute on and then 1 minute off once a day for a week (either by biking or jogging). 

I wanted her heart rate to get above 151 bpm, so she would be in zone four  or higher. The goal of this style of training was to get her body used to moving faster and more intensely, which would improve her VO2 max. 

Results

Both individuals were able to improve their performance. The first client set a one-hour personal record (PR) and raised his VO2max to 53 ml/kg/min). The second client is training consistently and has raised her VO2max to 41ml/kg/min. 

While graded exercise tests are not the only way to improve your client’s health and performance outcomes, they are an incredibly useful tool in determining how to optimize training regimes for different goals. By walking you through these examples, I demonstrated how to complete a graded exercise test, and what questions can be asked and answered using the report, both of which can then inform training recommendations.