The human body employs between 640 and 850 muscles. Some of these muscles are voluntary while others are operating without you even knowing. The heart is a cardiac muscle and an involuntary muscle. It just keeps beating without us having to initiate or oversee anything. Voluntary muscles are known as skeletal muscles because they attach to your bones and work in partnership with your bones to allow you to walk run, push things, pull things, bend over, etc.
All muscles, whether involuntary or voluntary are essential for human health. While being healthy will have an impact on your involuntary muscles, more effort is required to keep skeletal muscles at the top of their game.