Earlier in my RPG career I remember arguing with several GMs about wanting to be able to use acrobatics, or some other dexterity/agility related stat/skill. Every system I've ever seen - that has stats for your physical capabilities - disagrees with me on this. Climbing is always strength related, and several of those GMs were kind enough to explain it to me and how moving against gravity was an act of strength, not dexterity. Recently I came to the conclusion that I half agree with those GMs. Climbing should not be dexterity, but strength is also a poor way to represent it as well. Today I want to talk about that, and see whether or not you agree with me.
The Visible Problem With Strength
The visible problem with strength being used for climbing comes into play with the fantasy of the low strength, dextrous rogue character as depicted in every aspect of fiction from ninja stories to high fantasy tales involving rogues and thieves. The lithe, quick, knife fighter that does acrobatic tricks is often described as being able to climb like a spider. They scamper up walls and around ledges with the same grace and speed they do everything, leaving all their companions behind - even the big, strong heroes.
It seems strange to me that every RPG I've seen is incapable of depicting this very common aspect of the fiction the games are meant to be inspired by without some sort of bandaid - like Thieves in 5E not moving at half speed while climbing as a class ability. However, why Strength is uses does make sense on a quickpass, and we need to understand why that is before we can explain why it's not the ideal stat.
Why Strength Makes Sense
Strength makes sense for climbing because in the moment to moment aspect of climbing, effectively your character is Push/Pull/Lifting their body weight up the surface. If a character said they wanted to pick up a box that weighed 200 pounds, you wouldn't have them make a dex check would you? No, you'd have them make a strength check - if you had them make a check at all. So it stands to reason that when a person wants to lift their 200 pound frame up a wall you'd cal for strength, right?
Where This Falls Apart
Where Strength makes sense, and where it falls apart is made obvious with that specific conceptualization of what climbing is. Assuming characters with equal stats, you would likely assign a higher difficulty check for someone wanting to life a 300lb weight as opposed to a 100lb weight, correct?
Therefore it stands to reason that the high dex, low strength rogue that weighs 150lbs total with all their gear would have an easier time climbing a wall than the 300 pound+ Dragonborn fighter in heavy armor with a two handed weapon, correct? Now, obviously the Dragonborn's greater strength would help mitigate this difference, but they would still have the higher difficulty. Except no system does climbing checks this way.
Climbing check DCs is always based on the difficulty of the climb itself. A rope, or knotted rope, is generally the easiest difficulty in the game, with difficulty scaling up from there with things like sheer walls and overhangs being at the highest difficulty. The relative weight of the person trying to climb doesn't even factor into it.
Who Can Do A Pull Up?
While a little overly simple, we can assume that anyone who is capable of doing a pull up should be able to climb something in theory. Perhaps only something very small (like a ledge they can reach overhead), but they can perform the physical requirements for climbing. Right?
Most systems assume an average stat to be someone at least moderately physically fit. So it stands to reason that someone with an average strength, that is otherwise unburdened, could do a pull up, right?
More granular systems will flat out tell you the weight someone with strength X can lift, push, pull, or carry. If their strength enables them to lift their own body weight, the system is telling you that without a check being necessary this person can pull their body up some surface provided adequate handholds.
To break this down simpler: unless a character has a below average strength score (i.e. they get mechanical penalties, or what the game determines to be below average) they should be able to climb something when unburdened without a check.
Climbing Is Actually An Act of Stamina
Climbing a length of rope, a wall, or anything else is actually an act of stamina. Assuming you can even make some upward progress (see the above section) meaning the check is even possible, climbing is a race between your progress, and your endurance. You can see this in several videogames like Shadow of the Colossus and Legend of Zelda: Breath of the Wild where you have a "grip meter" that depletes over time. You can see this watching Ninja Warrior (the Japanese or American ones) where people fall off in the middle of obstacles, not because they're incapable of navigating the obstacle, but because their muscles give out before the obstacle is complete. Anyone who has gone rock climbing can also attest to this, and it is part of the reason why people will takes rests partway up, letting their arms hang loose and free. They're giving their muscles a rest so that they can continue up, much the same way that people will slow down or stop when running to catch their breath before starting up again.
The only time strength should be involved is if it is questionable that a character could even lift themselves/their gear. You could handle this either with two checks (simpler in a game like D&D and Pathfinder where this just requires rolling a second D20) where the Strength check determines if you make upward progress, and the Constitution check determines if you fall. Doing it this way, the constitution check should get harder with each check (making a climb something of a skill challenge) and enabling the person to 'rest' a round to reduce the difficulty of the next con check. Or you could just have the person roll the lower of the two stats, and go with that since a chain is only as strong as its weakest link.
While a single act of moving upwards is indeed strength, the base line abilities of an average statline should allow an unburdened character to lift themselves up. The act of climbing is actually an act of stamina/endurance, and as such should be tested against Constitution/Stamina/Resolve or whatever stat represents a character's physical tenacity.
Do you disagree? I'd love to hear why.