local Humanoid = game.Players.LocalPlayer.Character:WaitForChild("Humanoid")
local UserInputService = game:GetService("UserInputService")

UserInputService.InputBegan:Connect(function(input)
	if input.KeyCode == Enum.KeyCode.LeftShift then
		Humanoid.WalkSpeed = 40
	else
		Humanoid.WalkSpeed = 16
	end
end)