VO₂max for HYROX‑style racing: what to measure.

A HYROX race alternates eight 1 km runs with eight functional stations, from a ski ergometer and sled push and pull to rowing, carries, lunges and, last, wall balls.¹ Brandt and colleagues timed 11 recreational athletes (27% women) through a simulated Individual Open race and measured heart rate, blood lactate and perceived effort throughout.¹

• It is long and mostly running. The median finish was 86.5 minutes. The runs took 51.2 minutes of that, the stations 32.8.¹
• It is hard almost all the way. About 80% of the race (median 79.5%) was spent at "very hard" heart-rate intensity, and most of the rest at "hard".¹
• The stations cost more than the runs. Peak blood lactate was higher at the stations (median 8.5 mmol/L) than on the runs (7.7 mmol/L). Heart rate, lactate and perceived effort all peaked at the final station, wall balls.¹

The athletes' VO₂max was measured in a lab, on a treadmill ramp with a metabolic cart. The median was 51 ml/kg/min (range 46.6 to 72).¹ Higher VO₂max went with a faster overall finish (Spearman's ρ = −0.71). So did more endurance training and a lower body-fat percentage.¹ VO₂max was related to run time, but not to time spent on the stations.¹

The authors list the limits themselves: a small sample, athletes racing alone without competitors or spectators, runs on a treadmill rather than a track, a sled that differed from the competition sled, one division only, and no direct test of lower-body strength.¹ A larger registered study of the physiology and performance of HYROX athletes is listed on ClinicalTrials.gov.²

They answer different questions. VO₂max is the most oxygen you can use, your ceiling. A race that lasts well over an hour is not run at that ceiling: it is run just below the point where breathing and effort stop being sustainable.

That point is close to your second ventilatory threshold, VT2. Below your first threshold, VT1, effort is easy and you can talk in full sentences. Between VT1 and VT2 is steady, hard work. Above VT2, effort can only be held for a short time.^3,4 Measured in a ramp test, both thresholds come with your own heart rate and running pace at each, so you can set run pace and check whether a station has pushed you over VT2. See VT1 and VT2, explained.

The study above found about 80% of the race at very hard heart-rate intensity.¹ That is one reason a measured VT2 is useful: an age-formula heart-rate zone can be far from your own threshold.⁵

Looking for a test in India? See VO₂max testing in India.

• Retest at the end of a block, not every week. Training studies measured VO₂max change after 6 to 20 weeks.⁸
• Know your own noise. In one small 2026 study (six well-trained men cycling just below their first threshold, five systems), day-to-day variability in V̇O₂ was 3% to 12% (one system excluded), roughly 60–70% of it from the person.⁶ Maximal tests may differ, so treat a change smaller than the noise you see in your own repeat tests as possibly no change.
• Keep the test the same: device, protocol, time of day, food and caffeine, and treadmill rather than bike if you want run paces.

• The current engineering build records supervised room-air bench sessions only, with the analyzer off-face. Ramp tests are planned for later builds.
• The current flow element is characterised to about 85–100 L/min of ventilation. Trained athletes often breathe 150–200 L/min at VO₂max, so a maximal ramp is beyond it. A high-flow element is in development and will be validated separately. Known limitations.
• No accuracy figures yet. VenTracer will be validated side by side with a laboratory metabolic cart before any accuracy claim.ⁿ³ The validation plan.
• Testing during a race simulation (stations, wall balls, sled) is not something we plan to claim.

Until then, a lab ramp test with a metabolic cart is the way to get your VO₂max and thresholds measured. If you coach hybrid-fitness athletes and want to hear when VenTracer can test them, join as a coach.

1. Brandt T, Ebel C, Lebahn C, Schmidt A. Acute physiological responses and performance determinants in Hyrox© – a new running-focused high intensity functional fitness trend. Front Physiol. 2025;16:1519240. Published 31 March 2025.
2. ClinicalTrials.gov. Physiological and Performance Characteristics of HYROX Athletes. NCT07873840. Accessed October 2026.
3. Keir DA, Fontana FY, Robertson TC, et al. Exercise intensity thresholds: identifying the boundaries of sustainable performance. Med Sci Sports Exerc. 2015;47(9):1932–1940.
4. Seiler S. What is best practice for training intensity and duration distribution in endurance athletes? Int J Sports Physiol Perform. 2010;5(3):276–291.
5. Iannetta D, Inglis EC, Mattu AT, et al. A critical evaluation of current methods for exercise prescription in women and men. Med Sci Sports Exerc. 2020;52(2):466–473.
6. Van Hooren B, Souren T, Miqueu F, Bongers BC. Technological and biological reliability, and validity of five different CPET systems during simulated and human exercise. Scand J Med Sci Sports, 2026.
7. Molina-Garcia P, Notbohm HL, Schumann M, et al. Validity of estimating the maximal oxygen consumption by consumer wearables: a systematic review with meta-analysis and expert statement of the INTERLIVE network. Sports Med. 2022;52(7):1577–1597.
8. Bacon AP, Carter RE, Ogle EA, Joyner MJ. VO₂max trainability and high intensity interval training in humans: a meta-analysis. PLoS One. 2013;8(9):e73182.