How many muscles are in the human body? The answer may surprise you.

The human body is a wonderous thing, especially when you consider how intricate and efficient each bodily system is. For instance, an adult’s blood vessels could encircle the earth 2.5 times if connected end to end; the human nose is capable of recognizing more than a trillion different scents; and a human heart beats more than 3 billion times in an average lifespan.

But among the most impressive systems of the body is the musculoskeletal system and all its muscles, ligaments, bones, tendons and connective tissue. This system allows us to move about freely starting with climbing out of bed each morning and then getting to school, work or play, followed by all the countless activities and movements that follow.

How many muscles are in the human body?

So, how many muscles make up this vast system of tissue, strength and mobility? It turns out the answer is not as straightforward as one might think, says James Smoliga, DVM, PhD, the director of research and faculty development for Tufts University School of Medicine Seattle Program. "The numbers vary," he explains, with some experts saying the body has close to 600 muscles and others saying it may be as many as 840.

He says this discrepancy exists because "anatomists have different ways of deciding whether a given muscle is one muscle with multiple parts or if it should be considered multiple distinct muscles."

Adding to the confusion is that every now and then, researchers discover another new muscle such as what happened with a 2022 study and a newly defined muscle in the jaw. Because of such factors, most sources report on the safe side that there are at least 600 muscles in the human body.

No matter how you count them though, it's known that the smallest muscle in the body is the stapedius muscle - a muscle located within the middle ear that's not even ¼ of an inch long. The largest muscle is the gluteus maximus and it has important functions such as helping with the rotation of the thigh and hip joint. "Unfortunately, many people have sedentary jobs which require a lot of sitting and can lead to weakness in the core and gluteal muscles of the body that can ultimately lead to increased susceptibility to injury," says Matthew Anastasi, MD, a consultant within the division of sports medicine department of orthopedics at Mayo Clinic in Arizona.

What are the main types of muscle?

All muscles in the human body fit into one of three types or categories: "skeletal, smooth, and cardiac," explains Eric Hegedus, PT, PhD, a professor of rehabilitation sciences at Tufts University School of Medicine. Skeletal muscles are the lean muscle tissue attached to one's bones, usually by tendons. Smooth muscles consist of the tissue located in various internal structures such as one's arteries and digestive tract. And one's cardiac muscle is the muscle tissue specific to the heart.

Hegedus says each muscle type is distinguished by different functions. "The muscles you can see that give our body its shape and help us move are skeletal muscles; the ones that mostly function without us thinking about them are smooth muscles; and cardiac muscle is, of course, the heart."

How to strengthen and protect muscle

For muscles to function properly requires care, protection, and at various life stages, strengthening. For cardiac and smooth muscles, that means taking care of our heart and digestive system and not consuming products that could do bodily organs harm. When it comes to skeletal muscles, "aerobic exercises such as running and swimming are fantastic ways to work and strengthen (them)," says Anastasi. Exercise should also include weightlifting or resistance training, which Hegedus says "is the single most important thing you can do to maintain quality of life as you age."

Indeed, such exercise not only strengthens each targeted muscle group but can also help smooth and cardiac muscles as well since muscle growth demands more oxygen-rich blood which makes one's heart beat faster to keep up.

Another way to strengthen and protect one's muscles is through proper stretching. "Flexibility decreases with age and therefore all major muscle groups should be stretched at least two to three times per week," advises Anastasi. He adds that stretching on a regular basis also maintains and may even increase one's flexibility, "which helps to keep a normal range of motion for all of your joints."

And even if your interests or movement capabilities are limited, Smoliga says you can still improve the health and function of your muscles by staying active. "The most important thing is trying to participate in physical activity, which engages your muscles beyond that which you would do from activities of daily living," he says. "Doing something is better than doing nothing."

More: Your blood pressure may change as you age. Here's why.

This article originally appeared on USA TODAY: How many muscles are in the human body?