The interference effect myth: you can train strength and cardio together

The myth: strength and endurance in the same session cancel each other out. The "interference effect" dominated gym lore for decades — do both and you'll get good at neither. It made HYROX athletes anxious about a sport that is, by definition, both.

Debunking it

The concrete proof: Schumann and colleagues' 2021 meta-analysis found that concurrent aerobic and strength training did not impair the development of maximal strength or muscle size compared with strength training alone. Only explosive (power) development took a modest hit — and HYROX rewards strength endurance, not a max vertical jump.

In other words, the exact thing HYROX requires — a strong aerobic base plus strength endurance — is well supported by combining them. Believing the myth makes you over-separate your training and under-train the race's real demand: doing both while tired.

What to do instead

Combine deliberately. If you want to protect each quality, separate the hard strength and hard endurance sessions by 4–6 hours when your schedule allows. As race day nears, do the opposite: combine modalities in one session (run, then station work, then run) to build sport-specific fatigue resistance.

Tip 1: Same day is fine — spacing beats skipping.
Tip 2: Put the priority quality first when it's fresh.
Tip 3: In the final weeks, blend running and stations to mimic the race.

Keep reading

• Is HYROX strength or cardio?
• Runner vs CrossFitter: who's built for HYROX?
• How to build your HYROX aerobic base
• Free 8-week HYROX plan