These days, the internet is buzzing with advice that while money and insurance are good, you should build muscle before it's too late.

At first, I didn't understand. I thought that to live long, the heart and blood vessels were important, so what does having thick thighs have to do with lifespan?

But it turns out that muscle isn't just the flesh we use for strength.

In particular, the thighs and glutes are said to be crucial. I wondered if I really needed to work on my glutes at 60, but these are where the largest muscles in our body are concentrated.

They are responsible for walking, climbing stairs, getting up from a chair, and even stabilizing us when we stumble.

When you're young, having a bit of weakness in your legs isn't a big deal. But when you reach your 60s and 70s, your walking speed slows down, and if your balance decreases, the risk of falling increases.

If you happen to injure your hip joint, you'll end up lying down, which leads to more muscle loss, and with less muscle, you can't walk as well. It's a vicious cycle that can easily lead to death.

Muscle also acts as a factory for processing blood sugar. Skeletal muscle is a key tissue that receives and stores glucose from a bowl of rice.

Regular use of muscles can also help improve insulin sensitivity.

That's why it's not pleasant to see a body shape where the belly sticks out and the limbs become thin as you age. Your weight may be the same, but you could have lost muscle and replaced it with fat.

The true value of muscle shows when you're in pain. When a major surgery or infection occurs, the protein in your muscles becomes a resource that supplies amino acids needed for recovery.

It may seem insignificant in everyday life, but in a crisis, it's like having emergency funds to draw upon.

The same goes for arm muscles. Carrying a shopping bag, opening heavy doors, lifting your body, and catching yourself when you fall all rely on upper body strength.

This is one reason grip strength is used as an indicator of overall health.

That said, I'm not saying you should suddenly become a bodybuilder at 50. I'm not suggesting you should be kicking a soccer ball around at 60 either.

By 70, being able to get up from a chair without making a fuss when going to the bathroom alone, and by 80, being able to drive and carry grocery bags home is enough.

This may seem trivial, but as you age, it becomes an incredible asset.

Walking and cycling are good, but to maintain muscle itself, it's beneficial to do lower body exercises like squats and stair climbing, as well as upper body resistance exercises like push-ups and rows.

Eating enough protein and resting are also part of the exercise.

I now think of building muscle as creating a personal health insurance policy within my body.

If the money saved in youth is for retirement living expenses, then the muscle built from your 40s and 50s is your physical insurance for old age.

What's truly frightening about aging isn't just a few more wrinkles on your face.

It's not being able to walk on your own, even though you have two legs.