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)