Why does my blocking script not work when damage is inflicted?

for some reason my blocking script does not work, it makes the humanoids health infinite and it dies when 100 damage is inflicted.

local userInput = game:GetService("UserInputService")
local players = game:GetService("Players")

local sprintSpeed = 30 
local walkSpeed = 16 

local player = players.LocalPlayer

local function beginSprint(input, gameProcessed)
	if not gameProcessed then        
		if input.UserInputType == Enum.UserInputType.Keyboard then
			local keycode = input.KeyCode
			if keycode == Enum.KeyCode.F then 
				player.Character.Humanoid.MaxHealth = math.huge
				player.Character.Humanoid.Health = math.huge
			end
		end
	end
end

local function endSprint(input, gameProcessed)
	if not gameProcessed then
		if input.UserInputType == Enum.UserInputType.Keyboard then
			local keycode = input.KeyCode
			if keycode == Enum.KeyCode.F then
				player.Character.Humanoid.MaxHealth = 100
				player.Character.Humanoid.Health = 100
			end
		end
	end
end

userInput.InputBegan:Connect(beginSprint)
userInput.InputEnded:Connect(endSprint)

I think this will work:

local userInput = game:GetService("UserInputService")
local players = game:GetService("Players")

local sprintSpeed = 30 
local walkSpeed = 16 

local player = players.LocalPlayer

local function beginSprint(input, gameProcessed)
    if not gameProcessed then        
        if input.UserInputType == Enum.UserInputType.Keyboard then
            local keycode = input.KeyCode
            if keycode == Enum.KeyCode.F then 
                player.Character.Humanoid.MaxHealth = math.huge
                player.Character.Humanoid.Health = player.Character.Humanoid.MaxHealth
            end
        end
    end
end

local function endSprint(input, gameProcessed)
    if not gameProcessed then
        if input.UserInputType == Enum.UserInputType.Keyboard then
            local keycode = input.KeyCode
            if keycode == Enum.KeyCode.F then
                player.Character.Humanoid.MaxHealth = 100
                player.Character.Humanoid.Health = 100
            end
        end
    end
end

userInput.InputBegan:Connect(beginSprint)
userInput.InputEnded:Connect(endSprint)