Hyrox Events: Why a Cooling Tub Must Be at Every Medical Post

After the death of a 28-year-old woman at Hyrox Eurexpo Lyon on 25 May 2026, the question of medical equipment at Hyrox events has become impossible to avoid. Ice baths were available at Lyon's medical station. They successfully treated several hyperthermia cases. But they were not enough for the most severe case. What could have made the difference?

What ice baths at a medical station cannot do alone

Media coverage of Lyon mentioned "ice baths at the medical station". That is a good starting point — it shows the medical team had anticipated thermal risk and had a cooling method available.

But there is a fundamental difference between ice baths used for cooling and a medical-grade emergency cooling tub compliant with the reference protocol.

The reference protocol — validated by the ACSM, SFAR and IOC — requires whole-body immersion: shoulders and scalp submerged, airway maintained above water by attending medical staff. This immersion must be maintained until rectal temperature returns below 38.6°C, measured every 5 minutes.

A bag of ice placed on the body, or cold water spraying, does not constitute whole-body immersion. The cooling rate achieved is 0.03°C/min — versus 0.35°C/min for full immersion. For a patient at 42°C, the difference between the two methods is the difference between 10 minutes and over an hour to reach 38.6°C. The therapeutic window is 30 minutes.

The Cool First Transport Second protocol applied to Hyrox

The medical rule applies identically to an indoor Hyrox event and an outdoor marathon:

1. Recognition — collapse during intense effort + temperature ≥ 40°C + neurological signs = presumed EHS.

2. Immediate cooling — deploy the tub, fill with cold water and ice, whole-body immersion. No transport before cooling.

3. Call EMS in parallel — SAMU informed of cooling in progress, not before.

4. Stop at 38.6°C rectal — then transport to emergency department for blood work.

The deployment speed of the tub is critical. Every minute lost between collapse and the start of immersion is a minute where core temperature remains above 40°C.

What every Hyrox organiser must put in place

Before the event

Thermal risk assessment — even indoors, calculate the expected heat load based on participant numbers, floor area and air conditioning capacity. During extreme outdoor heat, indoor heat load can exceed air conditioning capacity.

Cooling tub provision — minimum 1 deployable tub per advanced medical post. For a large-scale Hyrox event (several thousand participants over multiple days): 2 to 3 units.

Cold water and ice stock — plan for daily replenishment. A cooling tub requires approximately 200 to 300 litres of water at 5–15°C and 20 to 30 kg of ice.

Rectal thermometers — at least one per medical post. Essential for safely triggering and stopping cooling.

Medical team training — Cool First Transport Second protocol, tub deployment, cooling stop criteria.

During the event

Active triage — identify participants who are slowing, stumbling, appearing confused, or stopping sweating. These are the early signs of EHS before collapse.

Tub in standby position — do not wait for an emergency to deploy. In standby configuration, the tub can be filled and operational in under 2 minutes.

Radio communication — first responders on the course must be able to contact the advanced medical post immediately without losing time.

The organiser's liability

In French law, the Lyon death will likely lead to an investigation into the medical conditions of the event. Regardless of the conclusions of that investigation, this incident redefines the standard of care expected at Hyrox events.

An organiser without an immersion tub compliant with the reference protocol cannot claim to have met the recommendations of the ACSM and IOC — which are now the professional standard.

Kollder in the Hyrox event medical setup

Kollder is designed for the specific requirements of indoor fitness events: rapid deployment in a confined space, single-person operation, compact profile between uses, full patient access for advanced medical procedures.

For Hyrox and fitness event organisers who want to act before the 2026 summer season: kollder.com/#contact.