Why Hyrox Is Destroying Your Physique

Summary

0:00 — Why HYROX may not build muscle

Ash Allen argues that HYROX is primarily an endurance event, not a reliable way to build the muscular physique often seen in race photos. People who already have substantial muscle may gradually lose some while preparing, especially if their running volume rises and their recovery or food intake is insufficient.

0:43 — Running is the biggest part of the race

A HYROX event consists of eight 1 km runs, each separated by a workout station. Allen says a simulated-race study found that running accounted for 59% of athletes’ total time. He also cites Hunter McIntyre’s race split—29 minutes of a 53-minute race spent running—and research suggesting that running strongly predicts finishing time.

His takeaway is that competitors need to train to run well, which means accepting a substantial endurance-training load.

1:46 — The interference effect

Combining cardio and strength training can make muscle-building harder, Allen says, particularly when running is frequent or lengthy. Running’s repeated impacts can add fatigue and muscle damage without providing the same growth stimulus as focused resistance training.

The effect is gradual: running does not necessarily erase muscle, but it can make it harder to recover and maintain it.

2:56 — Why elite HYROX athletes look muscular

Allen says many top athletes built their physiques before focusing on HYROX, often through CrossFit or weightlifting. He gives Willy Georges as an example: Georges reportedly weighed about 102–104 kg during weightlifting and around 85–86 kg as an elite HYROX athlete.

Allen cautions against copying an athlete’s current training without accounting for the years of lifting that came first.

3:37 — Stations may not bring muscles close enough to failure

Muscle growth generally requires sets to come close to failure, which Allen describes using “repetitions in reserve.” He argues that sled pushes and wall-ball throws often end because cardiovascular or muscular endurance gives out before the target muscles are close to failure.

Light weights can still build muscle, he notes, but only when sets are sufficiently challenging.

4:49 — Fixed loads limit progressive overload

To keep growing, muscles need progressively greater demands, such as more weight or repetitions over time. HYROX stations use fixed loads, while training is often geared toward completing them faster.

Allen uses the ancient legend of Milo of Croton carrying an increasingly heavy calf to illustrate progressive overload. Beginners may gain muscle initially from the novelty of training, he says, but those gains can stall when the stimulus stops increasing.

6:58 — The proposed solution: maintain muscle during race preparation

Allen advises keeping some strength training in the schedule during HYROX preparation. He says the minimum effective dose for maintenance can be relatively small, citing research in which young people retained muscle after substantially reducing training volume.

He describes a practical example of one weekly full-body session, with a few sets per muscle group and several reps left in reserve, while noting that needs vary.

8:57 — Build muscle in the off-season

For new muscle, Allen recommends a dedicated hypertrophy block rather than trying to maximize lifting and HYROX training at the same time. In his periodized approach, endurance work is reduced to a low, manageable level while strength training is emphasized.

As competition approaches, HYROX training increases and lifting shifts toward maintenance. He suggests placing the muscle-building phase in the months furthest from the race.

10:53 — Recap

Allen’s conclusion is that HYROX is a running-focused sport and is not, by itself, a dependable muscle-building program. To preserve muscle, maintain resistance training during race preparation. To add muscle, prioritize a separate strength-and-hypertrophy phase with progressive overload.

Presenter and sources

• Presenter: Ash Allen (Ash Allen Training)
• Sources cited or referenced: Brandt et al. (2025); Fast Talk Labs race splits; Rappelt et al. (2026); Held et al. (2026); Wilson et al. (2012); Schoenfeld et al. (2017); Bickel et al. (2011); Willy Georges’s reported weights via wod-science.
• Historical example: The legend of Milo of Croton.