Proprioception is the sense that lets us perceive parts of our own body. The location of our limbs, our posture, the angle of our joints, our overall movement, and actions we are taking. We have sensory receptors in our muscles, joints, and skin; and we are aware of how we command our muscles to move and perform actions.
With your eyes closed, can you touch your fingertips together? Keep your eyes closed (good job reading this) and do it again, but touch your fingertips behind your head. More challenging - a less familiar position, but still quite possible.
Everything that follows may lead you to the conclusion that one could really amplify an immersive experience through the use of crouching, ducking, crawling, jogging, flailing, kicking, and other such dramatic movements. This is largely ill-advised for obvious concerns of accessibility. Not just physical concerns, but immersive hardware - heavy displays, straps, cables - is largely not suited for fast motion or abnormal postures.
Don’t worry, you can still achieve impressive results with a subtle touch.
Posture And Space
When was the last time you built a pillow-fort, or holed-up inside of a tent? Small spaces where standing is impossible. Any space that is to small to stand up in feels incredibly small, and spaces that may just be large enough to stand comfortably can feel far larger than they really are.
Consider the common refrain of how small playgrounds or other childhood locations feel when one returns to them as an adult. This isn’t mere nostalgia, the environments really do feel disproportionately larger to children than adults.
I do not believe this extends or supports the idea that someone shorter feels like a space is larger or smaller than a taller individual, as we have all reached our own levels of calibration, so to speak. The size of a “regular room” is likely more informed by the rooms we have regularly experienced more than a variation in height by a foot or two.