How to fix while loop using humanoind.Running speed not breaking properly?

Speed changes constantly which fires many Running event, but the speed variable never changes in each fired thread, so you basically just spammed while loops in the process, which causes neverending counting.

You should only add an if condition to the event that only works when your speed is equal or above 16.

Added debounce to suit your needs - this'll stop the event from being executed until the debounce is disabled.

local debounce
humanoid.Running:Connect(function(speed)
    if speed >= 16 and not debounce then
        debounce = true
        --Do stuff heree
        wait(1) --Delay execution for a second
        debounce = false
    end
end)

EDIT: I guess you'll have to use a while loop after all... Here's something you can work with.

local spd = 0 --We shall update our speed here
local delay = 1 --Delay things by a second, there's a substitute I wanna share instead of using wait(1)

local debounce = 0 --Debounce can be anything!

local bValue = 0 --The one you wanna give but doesn't care how much you're trying to give.

--Use Heartbeat for a bit of precision
local runService = game:GetService('RunService')

--Here is everything you gotta do
humanoid.Running:Connect(function(speed)
    spd = speed --Updates to current speed
end)

--Now, use Heartbeat to increase the value
--I forgot your value name so I'll just call it bValue
--Edit: nvm it's correct
--This works pretty much the same way as while loops... but fires every after a frame of physics simulation is completed.
--Debounce here acts as a cooldown tbh
runService.Heartbeat:Connect(function(dt)
    --dt is delta time, it means the number of seconds that has elapsed since the last finished frame.
    --Now let's check if debounce is available.
    if debounce > 0 then
        --This must've meant that the script is delayed. Decrease debounce until it reaches zero, so during the next frame's completion it'll be run again.
        debounce = debounce - dt --in luau use debounce -= dt
        --Don't worry about debounce being under 0! We don't care about it if it is, technically.
    elseif spd >= 16 then --If debounce > 0 and the speed recorded exceeds 16
        debounce = delay --This basically tells the debounce to delay the process like wait()
        --Now add something to ur value
        bValue = bValue + 1
        --Print bValue and speed
        print(string.format('added bvalue by one, final result: %d\nSpeed is %d', bValue, spd))
        --you can put debounce = delay here in case the operation above may cause errors and you dont want it to be delayed if it is faulty
    end
end)

Also, the speed output may not be consistent - but if there's a reason for you to use it, I would say sure, don't hold your horses :d