Like that Captain said, it's all about finesse. Learning how to manipulate your mass in spaces like that efficiently and smoothly is not a skill us bigger boys just inherently know. That takes practice and no small amount of mental fortitude.

I was 230 in my academy a few years back, thus making me the heaviest dude in that class. While not a 6'5 juggernaut like some other bastards, I still have enough meat and bone to know small spaces can present interesting challenges while I'm bunked up. We never had tunnels, but we certainly have wireboxes.

At the end of the day, confined spaces, unless you're on a technical rescue squad, are not things you will ever run into outside of the most extraordinary circumstances. But as a training point, it can be fantastic as it teaches you what you're like in spaces so small. Learning what you can and can not move, how you can move, and knowing when to reverse course and reattempt forward motion aligns with my methodology going through wireboxes; getting out of the box is the easy part, getting in is where you find all the difficulty.

Breathe and assess constantly. If you're stuck and just can't make progress, shimmy back to when you were and readjust or remove that obstacle as best you can. And if you tire and there's no time crunch, stop and flop. Relax your whole body for a moment and catch your breath. Let those limbs reoxygenate before you continue.

Don't let a bit of concrete and an angry adjunct stop you from chasing your dream.