REF-902 · Gutiérrez-Hellín et al., 2026 · International Journal of Sports Physiology and Performance, pp. 1-8 · Paper · PubMed

Relative Running Intensity and Pacing During an Official HYROX PRO MEN Competition: The HYScience Study

Blimited evidenceMeasured on trained to highly trained athletesWritten before October 2026, being re-checked

Twenty-four men racing HYROX PRO did a maximal incremental treadmill test to fix VT2, vVO2max and VO2max, then within 10 days raced the official HYROX Madrid 2025 event. Speed on each of the eight 1-km runs and in the Roxzone (the transition area between stations) was expressed against their lab markers.

Running pace fell steadily from the first to the last run, the Roxzone was the slowest part, and across all running the athletes averaged about 84% of their VT2 speed and 76% of vVO2max — clearly below threshold.

The authors conclude that HYROX PRO running is submaximal and declines across the race, and that holding a higher relative intensity appears central to a shorter running time.

Participants

n=24 male HYROX PRO MEN athletes; race time 69:58 [5:05] min:s; VO2max 51.56 (5.00) mL·kg-1·min-1.

Protocol

Maximal incremental treadmill test: VT2, vVO2max and VO2max.
Within 10 days: official HYROX Madrid 2025 event.
Running speed for each of the eight 1-km segments and the Roxzone, and for the total running component (runs 1 to 8 plus the Roxzone, 8.70 km), in km·h-1 and relative to VT2 and vVO2max.

Key Results

Lab: VO2max 51.56 (5.00) mL·kg-1·min-1 (95% CI, 49.56 to 53.56); VT2 at 16.41 (0.87) km·h-1 (95% CI, 16.06 to 16.76); vVO2max at 18.08 (0.81) km·h-1 (95% CI, 17.76 to 18.40).
Running speed declined from 16.13 (0.97) km·h-1 in run 1 to 13.58 (1.02) km·h-1 in run 8; the Roxzone was slowest at 10.52 [1.18] km·h-1.
Mean running intensity across the eight runs and the Roxzone was 84.13% (5.54%) of VT2 (95% CI, 82.66 to 87.10) and 76.33% (4.05%) of vVO2max (95% CI, 75.31 to 78.55).
Run 1 (16.13 km·h-1) was just below the group's mean VT2 speed (16.41 km·h-1).
Authors' conclusion: running in HYROX PRO MEN is submaximal relative to VT2 and vVO2max and declines progressively; sustaining a higher relative intensity appears central to a shorter total running time.

Practical Application

To "how hard should I run the 1-km legs in HYROX?": in 24 male PRO racers, running averaged 84.13% of VT2 speed and 76.33% of vVO2max, starting near threshold pace (16.13 km·h-1 against a VT2 speed of 16.41 km·h-1) and falling to 13.58 km·h-1 by run 8. The legs are run below threshold even by trained men, and the pace fade is the norm, so the lever is how little the pace falls, not how fast the first kilometre goes.
Inference, not tested here: a runner whose VT2 speed is known can use "a little under VT2 pace" for the early runs as a ceiling; the study measured what athletes did, not what pacing is best.
The Roxzone was the slowest running in the race (10.52 km·h-1) — it counts toward running time. Inference, not tested here: moving briskly through transitions is cheap time.
Not from this paper; the base's own practice: train running straight off stations (compromised running, REF-589 by analogy with triathlon) and start the first kilometre controlled, as set out in SYNTH-71.

Limitations

Men only, PRO division, one event; women and the Open division are not covered.
Relative intensity is inferred from speed against lab markers; no heart rate, lactate or gas exchange during the race is reported in the abstract.
The link between higher relative intensity and shorter running time is the authors' reading; the abstract gives no correlation values.
Observational: which came first — fitness or the ability to hold pace — cannot be separated.
Author affiliations include HYROX Spain and hybrid-training businesses (affiliation noted from the record; no conflict statement was read).
Written from the abstract and record metadata only (full text not read).
How this entry was checked and changed
Why this level

observational, n=24, single race