Help with sprint script

Help and Feedback Scripting Support
#1

Hello, my sprint script causes the camera’s fov to “pulse”, and I’m not sure how to fix it.

local player = game.Players.LocalPlayer

repeat task.wait() until player.Character

local camera = workspace.CurrentCamera
local humanoid = player.Character.Humanoid
local UIS = game:GetService("UserInputService")

local debounce = false
local isRunning = false
UIS.InputBegan:Connect(function(input, isTyping)
	if isTyping then return end
	if input.KeyCode == Enum.KeyCode.LeftShift then
		if not debounce then
			debounce = true
			isRunning = true
			task.wait(4)
			debounce = false
		end	
	end
end)

UIS.InputEnded:Connect(function(input, isTyping)
	if isTyping then return end
	if input.KeyCode == Enum.KeyCode.LeftShift then
		isRunning = false
	end
end)

while true do
	print(humanoid.WalkSpeed)
	if isRunning == true then
		for i = 70,85,1 do
			camera.FieldOfView = i
			humanoid.WalkSpeed = 25
			task.wait(0.01)
		end
	else
		for i = 85,70,-1 do
			camera.FieldOfView = i
			humanoid.WalkSpeed = 16
			task.wait(0.01)
		end
	end
	task.wait()
end
#2

It’s because both for loops would be running at the same time, resulting in a “flickering/pulsing” fov.
Try using TweenService instead.