ctrl to sprint by zen

-- please give credit - zen

local player = game.Players.LocalPlayer
local character = player.Character or player.CharacterAdded:Wait()
local humanoid = character:WaitForChild("Humanoid")
local isSprinting = false
local normalWalkSpeed = humanoid.WalkSpeed
local sprintWalkSpeed = 30

local function startSprinting()
    if isSprinting then
        return
    end

    isSprinting = true
    humanoid.WalkSpeed = sprintWalkSpeed
end

local function stopSprinting()
    if not isSprinting then
        return
    end

    isSprinting = false
    humanoid.WalkSpeed = normalWalkSpeed
end

game:GetService("UserInputService").InputBegan:Connect(function(input)
    if input.KeyCode == Enum.KeyCode.LeftControl then
        startSprinting()
    end
end)

game:GetService("UserInputService").InputEnded:Connect(function(input)
    if input.KeyCode == Enum.KeyCode.LeftControl then
        stopSprinting()
    end
end)