Oh, but in terms of general design, children frequently aren’t factored in at all! Like, designing homes so that toddlers can comfortably exist, that’s one thing. But so a toddler-sized person can do adult-sized things, that’s much less often a concern. Little kids can’t always reach light switches or doorknobs, and with hands as little as theirs, they can’t manipulate standard scissors, and using general adult-sized tools (not just tools-tools, but just anything sized for an adult grip) would be awkward and/or painful, enough so that regular use could contribute to repetitive strain injuries. A kid, going to my work, they wouldn’t be able to reach the card readers, they wouldn’t be able to reach the door handles, they probably couldn’t move the heavier doors, a toddler couldn’t climb into my rolling chair without assistance, and a standard keyboard where I can touch-type wouldn’t be a good ergonomic fit for little kid hands.
So a kid can exist in an adult-sized environment, and they can do some things, but they’re facing massive disadvantages trying to do the same daily tasks using tools, buildings, etc. designed for an average adult. It’s something you hear about little people having to cope with if you read the right publications, but they’re outside that 5% female bound, so if there are constraints on the environment, they’re going to be one of the first groups to stop being actively accommodated. In human buildings, small people will FIT, because that’s how sizes work, but they’re going to struggle in other ways. On the flip side, a basketball player will… usually fit, because they aren’t too wide and high ceilings are relatively easy to do. But they’ll still have to duck to fit through doors, they won’t fit in compact cars, and they’ll struggle with things like airplane seats. Two kids in my freshman dorm hit their heads on their ceiling if they stood up straight. And people who are outliers in terms of width have their own problems in similar areas.
Plus the anthropometrics cover all sorts of dimensions like hand size and arm length, that all factor into the complete action profile needed to do any one of tons of everyday actions. The outliers who can get BY a lot of the time, but human accommodations for someone like a basketball player fall way short of robot accommodations for, say, Ultra Magnus.
Like, lemme talk in terms of military ships, because that’s a much more constrained environment. In a sub, you’re working with narrow halls, short little hatches, tiny bunks. A tall person simply won’t fit. You can get SOME height, but there’s a point where you just can’t serve on a sub if you’re too tall, because you can’t fit in the bunk. And a little person wouldn’t be able to serve either, because the environment is so constrained that things are too high for them to reach. Someone wide around is legit going to have trouble getting around because everything is so tight. A surface ship is much less constrained, but… still pretty constrained. You won’t run into as many of the issues, but the accommodations people build in just stop at a certain point, and if you tried to get them to account for a little person or a seven foot basketball player, you’d just get a shrug. And then something like a jet fighter is SUPER constrained in terms of who can pilot them, because this person needs to fit nicely into this very, very specific environment, and like hell they’re paying to redesign this expensive jet to fit more randos, that’s just not happening.
But this extends to more than plain dimensions. Ergonomic evaluations are just… super complicated, but it comes down to a statics/dynamics analysis of weight loading and stresses on various body parts. Even if a person CAN do something, is that task going to cause damage to their body over time? Even if a 5th percentile female can technically carry out the same LRU replacement maintenance task as a 95th percentile male, the physical dimensions of her body can SIGNIFICANTLY change those numbers from what that guy is going to experience. Her hand is littler than his, is this grip too wide for her? His hand is wider than hers, can it fit into the same tight area to do the task? If they’re lifting from five feet off the ground, she’s working at shoulder height and he’s working at chest height, and that’s going to affect their shoulders SUPER differently. Six feet off the ground? Oh my god, no, her shoulders will die, and you risk her dropping the thing right on her face. But go too low and the guy is going to have problems unless he kneels– and now fold that into your analysis too. Now account for weight, duration, frequency, periodicity, vibration, the rest of their body position, and any tools necessary for the task.
Just accommodating the 5th percentile female to 95th percentile male can get crazy hard. Even in terms of like, personal protective equipment. Standard equipment won’t work for everyone, even in terms of something as basic as glove size. And if you make PPE too uncomfortable/task-complicating, then people will go without and cause more safety risks. But specializing it to everyone ups your costs like whoa and introduces new problems if people use the wrong things or equipment goes missing and they have to make do with poorly fitted PPE. Small hands won’t be able to hold average sized grips well, and large hands won’t be able to comfortably fit into average grip spaces.
I’m all over the place, but a couple years ago I was head safety engineer for a big contract, working hand in hand with the full-on HSI engineers, and just trying to get the design engineers to size an LRU handle properly so an average sized hand could grab it was a multi-month fight. Explaining the weight limits for a single-person lift was equally painful. And the body stress analyses are complicated enough that analytic simulation tools look kind of… shockingly underdeveloped. Which they aren’t, a ton of work has gone into these things, the math is just so complicated to work out, even in a simplified way. I’ve done analyses that are literally laying a protractor on top of a photograph to see what angles people’s joints are making.
Haha, I’m really all over the place with this now :P But in a home environment, most humans can comfortably exist, even as extreme outliers. Once you start expanding out into stuff like driving (or other travel) or shopping or office work, you start running into issues, and once you hit a military/industrial environment, like large parts of the transformers universe are, human accommodations get surprisingly limited. It’s really interesting stuff, especially the raw theory of it, even though being the engineer raining on everybody else’s design parade is a fairly stressful experience.