In a groundbreaking collaboration at Adidas headquarters, elite functional fitness athletes underwent a revolutionary test that challenges everything we thought we knew about measuring cardiovascular capacity.
The question at the heart of this research: Are traditional VO2 max tests failing to capture the true aerobic capacity of CrossFit athletes?
What emerged was a testing protocol that might finally unlock the secret to understanding—and improving—functional fitness performance.
And the results could transform how athletes train for metabolic conditioning.
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The Problem With Traditional Testing
Back in 2024, researchers from the University of Basel profiled elite CrossFit athletes in laboratory conditions. They measured strength parameters and endurance capacity, specifically VO2 max values.
The results were surprising—and not in a good way. Male athletes averaged around 56 ml/kg/min, while females came in at approximately 52 ml/kg/min. These numbers seemed surprisingly low for world-class athletes.
This raised a critical question: Were these athletes simply not that aerobically fit, or was the test itself flawed?
Most VO2 max tests are done on a bike or treadmill. And also this test that we did in the lab was on a bike, a very controlled, very cyclical, a very predictable movement. But obviously in CrossFit there’s none of that.
CrossFit demands constantly varied movements, unstable positions, and rapidly shifting patterns. Testing athletes on a stationary bike might be like judging a basketball player’s ability by having them only run in straight lines.
Designing A Better Test
At the state-of-the-art Adidas sport science facility, researchers developed an innovative approach. They kept the concept of a ramp test to exhaustion but replaced traditional endurance modalities with functional movements.
The protocol was elegantly simple yet brutally effective. Athletes performed repeating five-minute EMOMs (every minute on the minute) with escalating intensity.
The Test Structure
- Minutes 1-2: Rowing at progressively increasing wattages (starting at 60 watts, increasing by 30 watts each round)
- Minute 3: Burpees to target (starting at 4 reps, increasing by 2 each round)
- Minute 4: Thrusters (11 reps until round 8, then increasing to 12, 13, 14)
- Minute 5: Rest
The test concludes when athletes can no longer maintain the prescribed watts on the rower or complete all repetitions within the minute.
The Secret Weapon: Motion Tracking Technology
Critical to this testing protocol was specialized equipment from WhatMotions—an IMU (inertial measurement unit) sensor worn on the chest and wrist.
This technology represented a genuine breakthrough. Using motion tracking and machine learning algorithms, the device automatically assesses functional movements in real-time.
More importantly, it estimates power output with remarkable accuracy, validated against laboratory measurements. This allowed researchers to standardize intensity across completely different movement patterns for the first time.
For the first time we can standardize the intensity across completely different movement patterns and that is purely because of this device that we can actually analyze and perform such a test.
The burpee-to-target variation was specifically chosen for standardization. Athletes jumped to a height proportional to their body height, ensuring fairness while maintaining consistency.
What The Data Revealed
Elite athletes pushed themselves to extraordinary limits. Some reached interval 9 or beyond, rowing at 450 watts while maintaining burpees and thrusters.
Lactate measurements told a fascinating story. Athletes maintained low lactate values (2.8-3.1 mmol/L) through the initial rounds, confirming the intensity remained sufficiently aerobic.
As rounds progressed, lactate began climbing. But what stood out was the athletes’ ability to continue working at high lactate levels—a specific adaptation to functional fitness training.
What is specific about CrossFit athletes is that you can go long in this high lactate zones. And that’s because you have a high tolerance to high density workouts.
Individual Differences Emerged
Different athletes showed distinct limiting factors. Some struggled most with rowing, particularly taller athletes who excelled at thrusters but found the rowing watts increasingly challenging.
Others maintained impressive efficiency throughout the test, using superior technique to conserve energy. This efficiency showed up clearly in the power output data.
One athlete noted his limiting factor clearly:
The row is so aggressive. That just turns into a max row for us. The thrusters, that’s a good movement for me. You have time on your side there. The row—I don’t know what 450 would equate to. Is that a sub 1:30? Yeah. Just I thought I had it in me for the burpees, but it just…
The Zone Two Mystery
One fascinating finding emerged regarding aerobic base training. CrossFit athletes demonstrated a large “yellow zone” between their first and second lactate thresholds—much larger than endurance or hybrid racing athletes.
This adaptation reflects how functional fitness athletes typically train. They spend considerable time in this moderate-to-high intensity zone, developing remarkable lactate tolerance.
However, this creates a unique challenge for zone two training. Because these athletes possess such well-developed aerobic systems, they must produce substantial mechanical power just to reach zone two intensity.
Traditional long, slow distance work becomes problematic—athletes get fatigued and bored from the sheer volume required.
Actionable Training Applications
The real value of this testing lies in practical implementation. Researchers used the threshold power data to prescribe specific repetition schemes for various movements.
By identifying the exact power output at both aerobic and anaerobic thresholds, they calculated how many reps of different movements would keep athletes in target zones.
A Smarter Approach To Conditioning
One innovative application involves mixed-modality zone two work. Instead of 90 minutes on an assault bike, athletes could alternate:
- 8 minutes of cycling at aerobic threshold
- 8 minutes of functional movements at prescribed low intensity
- Repeat for 60-90 minutes total
This approach builds aerobic capacity while allowing athletes to work on movement patterns and address weaknesses—without the mental fatigue of monotonous cardio.
Movement Efficiency Under Fatigue
The power output data revealed another crucial insight. Some athletes maintained consistent technique throughout the test, producing nearly linear power increases.
Others showed significant deviations, particularly after crossing their second lactate threshold. These inefficiencies under fatigue represent clear targets for improvement.
Those small variations, the deviations from the perfectly linear increase—they are due to changes in their technique or what they were actually doing. Some athletes have specific zones where they are more efficient, where they are able to move producing less power.
How You Can Use This Test
While access to laboratory-grade equipment seems out of reach for most athletes, the underlying protocol can be adapted for any gym.
The WhatMotions sensor is commercially available, allowing athletes to track their own movement efficiency and power output during functional fitness workouts.
Even without specialized equipment, the test structure provides value. Athletes can perform the exact protocol, tracking completed rounds and subjective fatigue to establish baselines and measure progress over time.
DIY Version
- Use a Concept2 rower with visible wattage display
- Set up a standardized burpee target at 120% of your height
- Select appropriate thruster weights (men: build to 45kg, women: build to 30kg)
- Follow the prescribed progression
- Record your final completed round
Retest every 8-12 weeks to track improvements in mixed-modal conditioning capacity.
The Future Of Functional Fitness Testing
This research represents a significant shift in how we understand and measure functional fitness capacity. Traditional cardio tests simply don’t capture the complex demands these athletes face.
By incorporating movement variety, tracking mechanical power output across different patterns, and measuring metabolic responses simultaneously, researchers created a more valid assessment tool.
Perhaps most importantly, the data generated isn’t just interesting—it’s actionable. Athletes receive specific training prescriptions tailored to their individual thresholds and weaknesses.
As one athlete reflected on the difference between this test and traditional assessments, the value became clear. This wasn’t testing for the sake of testing—it was performance optimization through precise measurement and targeted intervention.
The marriage of functional movements, advanced motion tracking, and metabolic testing may finally provide the tools to unlock peak performance in the constantly varied world of functional fitness.
