Default to concurrent. Block when you have a deadline. Most climbers aren't training toward a competition calendar: there's no date somebody else picked that you have to arrive sharp for, and without that date a block buys you surprisingly little.
Both structures work. They cost different things. A block protects intensity and spends drift in whatever you park. Concurrent protects everything and spends concentration on the quality that needs freshness most, which for climbers is usually max strength.
This is not which protocol to run
Choosing between max hangs, repeaters, and the rest happens inside one training slot, and our protocols comparison owns that question. This is about how the slots are arranged across weeks and months. You can run identical protocols in either structure.
Block: one thing at a time
A block structure gives one quality the priority for a stretch of weeks. Max finger strength, say. It gets the fresh sessions, the recovery budget, and the volume, while endurance and everything else drop to whatever keeps them from falling over. Then you switch.
What it buys. Concentration. Strength adaptation appears to be intensity-dependent, which is the finding behind our session order post: training at high intensities improved maximal finger strength while a lower-intensity group did not. Anything that quietly lowers your working intensity is eroding the exact stimulus you are chasing, and competing priorities lower intensity. A block is mostly a device for protecting intensity from everything else in your week.
What it costs. Detraining, and fragility. Whatever you park loses ground while it waits, and how much depends on how long the block runs and how close to nothing you let that quality drop. We're not going to invent a decay rate for you. Plan on picking it back up a step down from where you left it, and build that step into the next block rather than being surprised by it. Fragility is the sharper cost: a block schedules one stimulus for six weeks, so an illness, a work trip, or a tweak in week three eats a large share of the only work you had planned for that quality.
Concurrent: everything, all the time
A concurrent structure keeps every quality in the week at all times. Some finger strength, some endurance, some antagonist work, some skill, none of them getting the full weight of your attention.
What it buys. Robustness and simplicity. Nothing detrains because nothing was parked. A missed week is a missed week rather than a missed block. And you never have to answer the question of what to do if your season arrives while you are mid-endurance-phase.
Protects intensity
Protects everything
What it costs. Dilution. Every quality is competing for the same recovery, and the one that suffers most is the one that needs the most freshness, which for climbers is usually max strength. Run everything concurrently for long enough and you can end up in the specific frustration our log post describes as sawtooth with no trend: plenty of work, no direction.
The question is not which philosophy is correct. It is whether you have a deadline.
When a date appears, block
A trip you have booked. A season you want to arrive strong for. A specific project with a specific demand. That's what makes a block worth paying for, because a block is a bet: you're spending drift in everything you park to buy concentration in one thing, and the bet only makes sense when there's a date the concentration has to be ready by.
Several qualities will improve at once for most people, most of the time, and the robustness of concurrent work is worth more than the concentration until that date exists. You get to be ill for a week without losing a phase.
The three questions behind that
The rule above covers most people. If you want to reason it out for yourself rather than take ours, these are the things it actually turns on. We're not going to hand you a threshold like "under six hours a week, go concurrent". That number would be invented, and you'd be able to tell.
1. How many hard sessions can you actually recover from? Not fit in the diary. Recover from. The fewer you have, the worse dilution hurts, because splitting three hard sessions across four qualities means nothing gets a real stimulus. This is the argument that pushes time-poor climbers toward focusing. Our frequency post is the right lens: frequency follows load, not a rule.
2. How far away is your season? This is the deadline question again, in more detail. Months out, you can afford to park something and accept the drift, because there is time to bring it back, and that is the window where a block earns its keep. Weeks out, parking a quality you will need on rock is a bad trade, and the structure should be looking more like everything ticking over with the volume coming down. Our companion post on the training year covers that shape: off season you build, in season you maintain.
3. How long have you been training? Someone in their first year or two gets a response from almost any organised stimulus, so concentrating on one quality buys them little and costs them variety. Someone who has spent years training seriously usually needs a genuinely concentrated dose to move anything, because the early adaptations are already spent. Our timelines post explains why that gets harder as you go.
Answer those three and the structure tends to pick itself, and it usually picks the same thing the rule did.
What that looks like on two people
A climber with no trip booked, climbing twice a week and training twice, spends the year concurrent. Fingers, some endurance, some antagonist work, all of it present all the time, progressing slowly on each. Nothing is ever parked, so nothing ever has to be rebuilt, and when a good weekend appears they are ready for it because they were never mid-phase.
The same climber books three weeks somewhere steep and pocketed, far enough out to matter. Now there is a date. Fingers get the priority, the pocket positions get real attention, and the endurance work drops to whatever keeps it from falling over. That is a block, and it is worth the drift because the drift ends when the trip starts.
Same person, same tools, two structures, and the only thing that changed was whether a date existed. Notice there are no week counts in either sketch. How long a block runs depends on the person and the deadline, and a number here would be decoration.
Most climbers who ask this question end up somewhere in between anyway: one quality clearly prioritised, everything else kept alive on a maintenance dose, which is a block with the lights left on.
What both structures need regardless
- Progression. A structure is a container. If the load, volume, or difficulty isn't going up inside it, the container doesn't matter.
- A log you actually read. Neither structure tells you whether it worked. The log does, over a block, not a week.
- Deloads. Blocks make it easier to accumulate fatigue and easier to mistake that fatigue for a plateau. Our deload post covers telling one from the other.
- The same test position all year. If you change edges or grip positions between phases, you can't tell whether the structure worked or the test moved. See the testing post.
The bottom line
Block training protects intensity and costs you a little drift in whatever you park. Concurrent training protects everything and costs you concentration on the thing that needs it most. For most people most of the time, concurrent is the default, and the block is for when there's an actual deadline to aim it at. If you want to reason it out yourself instead, ask how many hard sessions you can genuinely recover from, how close your season is, and how many years of real training you're carrying. Then log it, deload it, and stop changing the structure every six weeks, which is the only approach that reliably fails.