Concurrent Training for Hyrox: How to Run and Lift Without Sabotaging Either (Training Science, Part 1)
Training for Hyrox means developing aerobic endurance and functional strength simultaneously. Science shows they can interfere with each other. Here is how to programme them together without compromise.
The interference effect
In 1980, Robert Hickson published a study showing that athletes who trained for both strength and endurance simultaneously made smaller strength gains than those who trained for strength alone. The “interference effect” was born.
In the 45 years since, the picture has become more nuanced — but the core finding is real. Concurrent training (doing both endurance and strength training) blunts some of the adaptations you would make if you did either in isolation. The question for Hyrox athletes is not whether the interference effect exists, but how much it matters and how to minimise it.
The short answer: at recreational training volumes (under 12 hours/week), the interference effect is real but manageable. The right programming structure significantly reduces it. Ignoring it — treating your Hyrox training as a random mix of runs and station work — leaves measurable performance on the table.
The full 5-part Training Science Series
New parts drop every 2nd day. Bookmark the Training Science hub to follow along.
- Part 1 — Concurrent Training for Hyrox: How to Run and Lift Without Sabotaging Either (you are here)
- Part 2 — Zone 2 Training for Hyrox: How Many Hours a Week and Why
- Part 3 — How to Peak for a Hyrox Race: The Final 4 Weeks
- Part 4 — VO2max Training for Hyrox: Intervals That Actually Transfer
- Part 5 — Deload Weeks in Hyrox Training: When to Back Off and What to Do
Why the interference happens
The molecular conflict sits between two signalling pathways: AMPK (activated by endurance exercise) and mTOR (activated by strength training and necessary for muscle protein synthesis).
When you do endurance work, AMPK activation promotes mitochondrial biogenesis and aerobic adaptations. It also suppresses mTOR — the signal that drives muscle growth and strength adaptation. If you do a long run and then immediately attempt a strength session, the elevated AMPK from the run reduces the anabolic response to the lifting.
Conversely, heavy strength work and the muscle damage it causes can impair the quality of subsequent endurance sessions through fatigue and reduced movement economy.
The interference is most severe when:
- Endurance and strength sessions are done in the same session (particularly endurance first, then strength)
- The endurance volume is very high (marathon training on top of heavy lifting)
- Sessions are not adequately separated by recovery time
The rules that minimise interference
Rule 1: Do strength before cardio in the same session
If you must do both in the same session, do strength first. The mechanism: strength training does not significantly elevate AMPK, so it does not suppress the endurance adaptation. But endurance work before strength elevates AMPK and blunts the strength response.
Practically: if you have one hour and need to do both, spend 35–40 minutes on strength and 20–25 minutes on cardio. Not the reverse.
Exception: Compromised running sessions are the deliberate exception to this rule. In a compromised run session, the goal is to train running while fatigued from stations — which is exactly the race-specific demand. This session is intentionally hard on the running quality.
Rule 2: Separate hard sessions by at least 6 hours
If you are training twice in one day, there should be at least 6 hours between a hard endurance session and a hard strength session. This allows AMPK levels to return to baseline and reduces the interference on the second session.
In practice, most athletes do not train twice daily. But if you occasionally do — a morning run and an evening station session — make sure the morning run is easy (zone 2) so AMPK elevation is minimal by evening.
Rule 3: Prioritise compound strength movements
The strength work in Hyrox preparation should be compound — squats, deadlifts, pull-ups, rows, overhead press. These create the most stimulus per unit of time and interference.
Avoid high-rep endurance lifting (3 × 30 of any movement). This creates the highest interference because it activates AMPK while also fatiguing the muscles you need for running. It does not build the strength you need for the sled and does not build the endurance the running does.
The ideal strength rep range for Hyrox: 4–8 reps for maximal strength development. This builds the foundation that the station-specific training then expresses.
Rule 4: Sequence the week so hard sessions do not follow each other
A well-sequenced training week looks like:
Monday: Hard strength session (squats, deadlifts, pull-ups) Tuesday: Easy run (zone 2, 45 min) Wednesday: Hard interval run (4 × 1km at race pace) Thursday: Station circuit at race pace — this is the compromised day, it follows hard running Friday: Rest or easy movement Saturday: Long run (60–80 min at easy pace) Sunday: Rest
What to avoid: hard strength session on Monday, hard interval run on Tuesday. The fatigue from heavy squats and deadlifts significantly impairs running economy for 24–48 hours.
The minimum effective dose of strength training
Many Hyrox athletes over-invest in running (which they know how to do) and under-invest in the strength that makes the stations manageable.
The minimum effective dose of strength training for Hyrox performance is 2 sessions per week of 45–60 minutes each. These sessions should focus on:
- Lower body compound strength: Squats and/or deadlifts (this builds the base for sled push, lunges, wall balls)
- Upper body pull: Pull-ups, rows, or SkiErg-specific cable pulls (for SkiErg, sled pull, farmers carry)
- Core stability: Farmer’s carry variations, front rack carries, plank variations (for all loaded carries)
More than 3 strength sessions per week starts to significantly impair the running adaptation at typical Hyrox training volumes. Two sessions is the sweet spot.
Why pure runners underperform and why pure CrossFitters underperform
The pure runner problem: Athletes with strong running backgrounds who only add station-specific circuits to their running base typically find their running splits are fine but their stations are 30–50% over target time. The stations require specific strength that general fitness does not provide. A 40-minute 10km runner who cannot do the sled push without stopping twice will not go sub-70 at Hyrox regardless of their running speed.
The pure CrossFitter problem: Athletes with strong CrossFit or functional fitness backgrounds who only add running to their existing training find the opposite. Their station work is often close to target. But their running economy — the metabolic efficiency of running — is underdeveloped. Running 8km of a Hyrox at the required pace requires specific running training. It is not simply cardiovascular fitness expressed through a different modality. Running economy is a trainable skill and it takes weeks of dedicated running to develop it.
Both problems have the same solution: actually train both, in the right proportions, with the right structure.
The interference effect in context
One final note: the interference effect is meaningful but not catastrophic. Recreational Hyrox athletes (the vast majority of Open competitors) are not approaching the ceiling of either strength or endurance adaptation. The interference effect is most significant at elite levels where marginal gains matter.
For the athlete going from sub-100 to sub-80, the interference effect is not your problem. Getting adequate training frequency, learning the station movements, and running enough kilometres are more important. Apply the rules above and do not overthink the molecular biology.
What’s next
Part 2 covers Zone 2 training — the aerobic base work that most Hyrox athletes skip because it feels too easy, and why that is a mistake.
→ Part 2: Zone 2 Training for Hyrox
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