Strength-limited or engine-limited? How to tell

You're limited by whichever half grades lower when both are measured on the same scale. Put your lifts against bodyweight standards and your VO2max against age and sex standards, and the lower one is the cap. If you race HYROX, your run and station percentiles are a second opinion. Then give your spare hours to the lower half, because under the combined score a point there is worth more than a point on the side you're already good at.

Put both halves on one scale#

"Am I strong enough" and "is my cardio good enough" are usually answered with two different rulers. A 140 kg squat and a 22-minute 5K don't compare until both are converted into the same thing.

The way hybridAF does it: strength grades your best barbell squat, bench, deadlift and overhead press against bodyweight, and engine grades your VO2max for your age and sex. Both land on the same ladder, where untrained is 20, novice 40, intermediate 60, advanced 80 and elite 95. Both halves are graded against published population data. Where the cut points sit and putting both on one ladder are our choices, and the science page says which parts are which.

You don't need the app to do this roughly. Look up your lifts in the hybrid athlete standards and your VO2max in the VO2max calculator, from a watch reading or a recent race. If one comes out "advanced" and the other "novice", you have your answer already.

The arithmetic: what one more point is worth#

The Hybrid Score combines the two with a harmonic mean, 2 × S × E ÷ (S + E), instead of an average. That pulls the result toward the lower half. Strength 60 and engine 90 average 75, but their harmonic mean is 72. Strength 75 and engine 75 is a straight 75.

The useful part is what that does at the margin. One more point of strength adds 2E² ÷ (S + E)² to the score. One more point of engine adds 2S² ÷ (S + E)². Whichever half is lower always has the bigger number.

Read that third row. When the halves are four points apart, the difference per point is small, 0.47 against 0.53. At 60 against 90 a point of strength is worth more than twice a point of engine.

It shows up even more clearly over a whole block. Take my October numbers, 74 and 57. Ten more points of strength would take the score to 67.9. Ten more points of engine would take it to 70.3. An average would call those two blocks identical, five points either way. The harmonic mean says the engine block is worth more, and the gap widens the further apart the halves are.

This is arithmetic about our score, not physiology. No published instrument validates combining strength and engine this way. We chose it because it makes the weak half impossible to hide, and the reasoning is in why the Hybrid Score uses a harmonic mean.

My numbers, twice#

Going into my first HYROX in August, my score was 77: strength 74, engine 80. Slightly engine-heavy. By the table above, a point of strength was worth 0.54 and a point of engine 0.46, so strength was the half capping me.

Then the race. HYROX is eight 1 km runs, each followed by one of eight workout stations ¹. I finished in 1:13:38, 197th of 3,254 men. My eight runs ranked 127th in that field. My eight stations ranked 406th ².

HYROX Bangkok 2026: where each part ranked

	Value (% of field (lower is better))
All 8 runs	3.9
Row	4.3
Burpee broad jumps	7.7
Sandbag lunges	10.3
SkiErg	21.7
Farmers carry	22.4
Sled pull	23.1
Wall balls	24.7
Sled push	29.7

Ken's rank in each part divided by the 3,254 men in the race. Ranks from HYRESULT, captured 2026-08-20.

Same shape as the score: engine ahead, strength behind. The heavy sled push was my worst-ranked station, 966th.

It isn't a clean split, though. The SkiErg, mostly an engine station, ranked 705th, down with the sleds and the carry. My row, also mostly engine, ranked 140th, nearly level with my runs. So "stations" doesn't equal "strength". The race agrees with the score on direction. It doesn't prove the score.

You can run the same check on your own race. HYRESULT gives the run total and the station total each a rank in the field. If your run rank is far better than your station rank, the stations are the weak half. Before you call that a strength problem, split the stations into the mostly-engine ones (SkiErg, row) and the load-heavy ones (sleds, farmers carry, lunges). Mine split both ways, which is the useful part.

Now October, and the picture has flipped. On 22 October my score is 64: strength still 74, engine down to 57. These numbers are on the current scoring model, which changed on 8 October, so they don't compare directly with the 77 from July.

Ken's two halves, October 2026

day of October	Strength (index (0 to 100))	Engine (index (0 to 100))
8	74	70
13	74	67
14	74	63
18	74	57
22	74	57

Daily snapshots on the current scoring model (from 8 October 2026). Source: Ken's hybridAF score history, read 2026-10-22.

The engine side only counts recent work, runs from the last 90 days and watch VO2max readings from the last 120, so it moves with what I've done lately. Lately has been steady 7 to 8 km runs at about 5:00 per kilometre. At 74 and 57, a point of engine is now worth 0.64 and a point of strength 0.38. The half that capped me in July is now the stronger one.

That's the honest answer to "which half caps me": it depends on when you ask. It's a measurement, not a personality type.

What the HYROX research says#

If HYROX is your event, the first published study of the race looked at what predicts finish time, and it points at the engine. Brandt 2025 ran 11 recreational athletes through a simulated race. Runs took 51.2 minutes of the 86.5 total. Faster times went with higher VO2max (rho -0.71), more endurance training volume (rho -0.68) and lower body fat (rho 0.67). Grip strength (rho 0.09) and resistance training volume (rho 0.34) weren't significantly related ³.

The stations behaved in a way a lifter would recognise. The heaviest ones, the sled push and sled pull, were the quickest to finish, with medians of 128 and 155 seconds. Wall balls, the last station, produced the highest heart rate, lactate and effort ratings of the race ³.

Treat it as a first look, not a verdict. Eleven people, racing alone, on a non-official sled, and grip was the only strength test ³. It also answers a different question. It says what tends to separate athletes across a group. It doesn't say which half is capping you. My race had the engine as the stronger half and the stations as the weaker one, which is exactly the case the group average hides.

hybridAF is not affiliated with HYROX.

Strength holds, engine fades#

The two halves don't age the same way in the score, and that matters for this question. Strength is graded from your best logged barbell lifts, with no recent-time window. Engine only counts runs from the last 90 days and watch VO2max readings from the last 120.

So if you stop running, the engine side drifts down on its own, and it can slide into being the cap without you noticing. If you stop lifting, the strength side holds its number, because the score has no way to know your squat has faded until you test it again. My strength has read 74 through six weeks of autumn training with no squats or deadlifts logged. That's a reason to retest a lift now and then, not a reason to believe nothing changed.

Does training the weak half cost the strong one?#

Probably less than you'd fear. Schumann 2022 pooled 43 studies and found adding aerobic training to a strength program didn't compromise maximal strength (SMD -0.06) or muscle size (SMD -0.01). Explosive strength took a small hit, mostly when both were done in the same session ⁴.

The other direction works too. Berryman and colleagues note that the interference effect hasn't been consistently reported, and that strength training can improve middle- and long-distance endurance performance, with a caveat that a badly planned block can hurt it ⁵. So moving hours to your weaker half doesn't mean giving the other one away, as long as the plan is sensible.

A rule of thumb for moving the number#

1. Grade both halves on one scale, from current numbers. A VO2max from last spring isn't current, and neither is a squat you last tested a year ago.
2. If they're within about five points of each other, the point values are nearly equal. Train for what your next race or block actually needs.
3. If the gap is bigger, the lower half gets the extra hours. Not all of them. Enough that it moves.
4. Recheck after six to eight weeks, because the cap can move, as mine did.

One catch. A point isn't the same amount of training everywhere on the ladder. The top band, from advanced to elite, spans 15 points where the bands below it span 20, so near the top each point takes more improvement to earn. A gap between 85 and 92 is harder to close than one between 55 and 62.

If you want the numbers without the algebra, the Hybrid Score calculator takes your lifts plus a run, a watch VO2max or a HYROX finish, and shows both halves and what one more point on each is worth. Once you know which half to feed, how to split a hybrid training week covers where the hours go, and how much lifting you need when you also run covers the dose. My full race is broken down in my first HYROX, and the rest of this cluster is on the hybrid training hub.