Health and movement — Wiki

Health regeneration, fall damage, getting shot, accuracy on the move, zoom, and how fast you run, sprint, aim, lean, crouch and jump.

You have 100 health.
It comes back: 5 seconds after you last took damage, all your missing health returns over one second. The recorded matches bear this out: players hit again within 5 seconds hadn't healed, and those hit again 7 seconds or more later were back to full.
Once your health has come back, the damage done to you before no longer counts as an assist.
Below 30 health the screen shows you're badly hurt.

Every hit kicks your aim, away from the shooter: about 0.5° per 10 damage at its peak, 0.05 seconds after the hit. It's over by 0.4 seconds.
Holding a Kar 98k doubles it, and a Springfield or a Kar 98k Sniper makes it 2.5 times as big.
Hits don't add up: the biggest one counts. All the pellets of one Trench Gun blast count as a single hit, with their damage added.
A hit from in front kicks your view up, and one from behind kicks it down. One from the side turns your gun.

You fall at 19.6 m/s², twice the Earth's gravity (the game's own gravity, 14 m/s², times 1.4 for players). Grenades fall just as fast.
Fall damage depends on how fast you land. Below 15.5 m/s it does nothing. From there it rises to 101 at 20 m/s and faster, which kills from full health. That's a drop of 6.1 m before it hurts, and 10.2 m or more to die from full health.
On Invasion, falling into the sea kills you.

You run at 4.75 m/s, times your weapon's own multiplier: 4.83 to 4.99 m/s. The table is on Weapons.
Forward is fastest: moving sideways you get 80% of that speed, and backwards 70% (read from the code; more on Hidden rules).
Sprinting is 7.12 m/s with any weapon. You can't sprint while leaning.
Aiming slows you to 40% of your run speed, times your weapon's aiming multiplier. That's 2.09 m/s with a scoped sniper rifle and 4.08 m/s with most guns.
Leaning slows you to 55% of your speed, and leaning while aiming slows you 10% more.
Crouched you move at 3.09 m/s, times your weapon's multiplier.
You reach full speed in 0.12 seconds (you accelerate at 40.5 m/s²), and let go of the keys and you stop in about a quarter of a second.
Slopes up to 46° are floors you can walk up; anything steeper is a wall. You walk up steps up to 45 cm high without jumping.
Crouching and standing up take 0.2 seconds.
On ladders you climb at up to 3.4 m/s.

A full lean takes 0.22 seconds, and so does coming back.
It tilts your view 20° and moves your eyes 39 cm to the side and 7 cm down: you lean round a corner from a pivot about at your waist.
Against a wall you lean less. The game checks 80 cm to the side you lean to, and stops your head about 10 cm short of anything there. Flat against a wall, you can't lean that way at all.
Lying down you lean only a fifth as far.
You can't sprint while leaning.
The BAR and the STG 44 are marked as heavy in the game, but nothing uses that mark. They slow you only through their own multipliers, like every other gun.

Fully aimed and on the ground, moving costs you no accuracy.
From the hip, holding a move key while moving faster than 1 m/s, or being in the air, opens your spread to its widest in a fraction of a second. Let go of the keys and it closes again, even while you're still sliding. The BAR and the STG 44 don't suffer it on foot.
In the air, aiming adds spread only in the first 0.3 seconds of aiming in.
After sprinting you can't fire for 0.3 seconds.
Each shot also turns your gun a little to one side: 0 to 0.2° by weapon, the same side for about 0.4 seconds at a time.
The gun kicking back and swaying on your screen is only the gun's model: it doesn't move your aim.

Your FOV setting (65 to 105, default 95) is your view from the hip.
Aiming zooms to the weapon's own field of view, times your setting / 90, so a gun's zoom changes little with your setting. The scoped Springfield and Kar 98k Sniper are always 23°, whatever your setting.
With head bob on, sprinting widens your view by 3°.

You jump at 6.55 m/s, the same with every weapon: your feet rise 1.09 m, and you land 0.67 seconds later on flat ground. Your speed across is kept.
A second jump within 2 seconds of the last one is lower: it starts at 1/1.3 of the speed, about 59% of the height.
Jumping while crouched stands you up instead.
Before jumping, the game tries to vault, but only where the map has a vault spot: a ledge 32 cm to about 2.16 m high, right in front of you. Elsewhere you just jump (Hidden rules, "Vaulting").
Shooting in the air adds spread (see Weapons).
In the air your keys still steer you, at a third of the push you have on the ground (two thirds when you're nearly still), and not into a wall you're touching.
Strafing in the air can make you faster than running. The game's movement comes from Unreal Tournament, with Quake's rule for the keys' push: it adds speed only while you're slower than your top speed in the direction you press, and nothing caps the speed it leaves you with. Turning as you strafe in the air builds speed; once you land, you slow back down to your normal speed.

Landing faster than 10 m/s, which takes a long drop rather than a normal jump, slows you for a moment: up to a second.
Landing hard again while you're still slowed halves your speed and slows you for 1.5 seconds.

Press the use key within 3 m of a weapon on the ground. You can't while you're planting or defusing, or where you could plant or defuse.