Here’s a shocker: at this moment, you possess a piece of technology more complex, advanced, miraculous, and valuable than anything that’s ever come out of Silicon Valley. It’s the product of millions of years of research and development, and an endless array of resources have gone into honing its functions.

But despite the brilliant complexity of this machine, it’s incredibly fragile. And even worse, it doesn’t come with an instruction booklet that teaches you how to use or maintain it.

The technology I’m hinting at is your body, and my goal as a trainer is to convince you that the simplest way to maintain this wonderful machine is to engage in regular resistance training.

Better known as lifting weights.

Sure, there are other forms of exercise, and each claims to be all your body needs to be fit, but it’s my mission in life to convince you that lifting weights is by far the most important thing you can do to maintain your body.

Other forms of fitness are wonderful accessories, but if you use only one tool, it should be resistance training.

The 10 basic components of fitness

Consider that there are ten basic components of fitness: strength, power, speed, stamina, flexibility, coordination, agility, balance, accuracy, and cardio respiratory endurance.

Other activities might check one or two boxes, but a well-developed resistance training regimen ticks nearly all of them.

But what about yoga? That counts, right?

Listen, I happen to love yoga. It’s the perfect way to disconnect from my frenzied life after a stressful day. And I know so many women (and men!) who do nothing but yoga to stay fit.

And you know what? Most of them are actually pretty fit.

Yoga gives them heaps of flexibility and balance—not to mention the endorphin rush of getting a good sweat going on—but they’re missing some of the most important pieces of the fitness puzzle.

And before you shout “Yoga makes me strong!” at your screen, understand that static holds are just a tiny portion of strength. And because you’re always pushing off of the floor, there’s no “pulling” component to the strength you build in yoga. And a healthy strength regimen should have a ratio of 3:1 pulling to pushing.

That means for healthy shoulders, you should do more pullups (yes, anyone can learn to do those) and rows than pushups and presses).

OK, but I already run

Running is another popular means of being fit, but in many cases it actually leads to injury and imbalance, which are really the opposite of fitness.

You’re certainly getting cardiorespiratory endurance when you run, along with stamina and, if you sprint, some speed. But again, you’re neglecting the most important pieces of the puzzle, all while engaging in a repetitive lower-body-specific movement pattern that lines the pockets of physiotherapists.

But don’t swimmers have the best bodies?

What could be wrong with swimming, right? It’s low-impact, it promotes strength and cardio endurance, and just look at the sleek physiques of those Olympians!

But prominent swimming coaches will tell you that 90 percent of swimming is upper body. The legs just trail behind you to keep you in line. Which means that if swimming is all you do, you’re neglecting the biggest, most structurally important muscles in your body.

And because no part of swimming mimics the rest of your daily activities, you’re not building a stable platform or any kinesthetic awareness to support your body as you age.

Why weight training matters

Now let’s look at weight training under the same microscope.

With a well-designed plan, you’re strengthening every structural and functional muscle in your body, including your heart if you lift with high intensity. You develop power from doing explosive movements like kettlebell swings. Stamina comes from high-rep sets. Believe it or not, you actually increase your flexibility when you lift with a full range of motion—few athletes are more flexible than Olympic weightlifters. Lifts like the Turkish getup give you agility and balance, while compound lifts like squats and deadlifts will test your coordination. Loaded throws also increase your accuracy, which means that with a well-balanced regimen, you’re hitting every aspect of human fitness—all within four one-hour sessions each week.

But even beyond those basic elements of fitness, lifting weights confers six key benefits better than any other form of exercise.

1) You’ll look better

Many women are scared of being too bulky, but as a figure competitor who’s been around a lot of bodybuilders, I can promise you that’s not going to happen without freakish genetics or heaps of steroids—even for a testosterone-filled man.

What lifting weights will give you is a symmetrical, aesthetic physique that burns fat while you rest—because muscle tissue is inherently metabolic.

Which means that if you lift weights, you’ll likely be leaner than someone who doesn’t lift.

2) You’ll live longer

We evolved to constantly move our bodies through strenuous motions in a varied landscape.

But in the modern era, we spend our days sitting at tables, sitting in cars, sitting at desks, and sitting on couches. We don’t climb, run, jump, push, or pull anything heavier than a fridge door, which means we’re constantly telling our bodies “Don’t worry—life is easy, and we don’t need to hang onto all that metabolically expensive muscle tissue.”

The result is too little muscle, too much fat, and the inability to climb stairs or withstand falls as we age. There’s no disputing that the more structurally sound your body is, the more likely you are to live a healthy, active life well into old age.

3) You’ll be smarter

This one surprises most people, because we have this idea of the average “gym bro” as a meathead who lives to grunt at women and flex in the mirror.

But research shows that training our bodies results in significant neurological benefits. By moving our bodies, we develop kinesthetic awareness and forge new neural pathways, enhancing our cognitive abilities.

Think of it this way: according to neuroscientist Daniel Wolpert, the animals with the biggest, most complex brains evolved all that gray matter for the sole purpose of complicated, adaptable movement. In general, the less an animal moves, the smaller its brain is.

So there’s a direct neurological relationship between how much you move, and how much your limited energy stores your body devotes to maintaining an active mind.

4) You’ll likely eat better

I’ve trained cyclists, marathoners, and swimmers who “carbed up” by crushing plates of pasta without ever considering how it might impact their long-term relationship with insulin.

But more often than not, when people start lifting weights seriously, the reevaluate their relationship with food to make sure all their hard work beneath a barbell is paying off. Because people who lift weights are often motivated by aesthetics—and because the vast majority of fat burning or fat gain is a result of dietary choices, lifters quickly become religious about their macronutrients and caloric intake.

They eat clean, count calories, and measure both what they put in their mouths and what it does to their bodies.

5) You’ll be more confident

Imagine you woke up every morning and climbed a mountain.

Think of the sense of accomplishment you’d constantly feel—especially if climbing that mountain gave you a defined physique that you can’t help loving when you look in the mirror.

On a small scale, that’s what lifting weights is all about. If you dedicate yourself to it and do it consistently, you’ll be constantly progressing and overcoming challenges, and it’ll give you you a tremendous sense of self worth.

6) You’ll be less stressed

I’m no stranger to stress, but when I’m having a rough day, nothing feels better than heading to the gym, turning off my human brain, and moving like an animal for an hour.

Not only does counting reps and focusing on movement soothe me, but the euphoric rush of endorphins that follows a good lifting session is like no other pleasure.

That’s why I lift. And that’s why I specialize in helping others learn to lift as well.