Weightlifting — also known as strength training or resistance training — is often thought of as the kid brother of cardio. Most people don’t see it as vital to their health in the same way as, say, running or stretching. Scientists don’t study it as much as they study endurance training.

When you tell people you’ve started running, they’ll say you’re taking care of your health. Tell them you’ve started weightlifting, and they’ll say you’re taking care of your looks. They couldn’t be more wrong. Strength training is one of the best things you can do for your health, athletic performance, and quality of life. Here’s why.

You Need Strength Training to Get into Your Best Possible Shape

If your workouts consist mostly or entirely of endurance exercise such as running or swimming, you’re not going to build very much muscle. And if you don’t build muscle, you’re going to have excess fat as well. People who do cardio without resistance training often find themselves falling into the skinny-fat trap, in which they’re at a healthy weight, but nonetheless have excess body fat and very little muscle mass.

Your body alternates between anabolic (tissue building) and catabolic (tissue breakdown) states. Ideally, you want to build muscle when you’re in an anabolic state and burn fat when you’re in a catabolic state, and that requires you to give your muscles an anabolic stimulus. While you may have gained some muscle when you first started endurance training, any muscle-building benefits of endurance training are short lived. Beyond a certain point, you have to be lifting weights.

The benefits of weight training go beyond improving your body composition. When you gain muscle, you raise your metabolic rate. For every pound of muscle you add, you burn an extra 7–10 calories per day just to maintain your body, as well as an extra 5–20 calories per hour when you work out.

Lifting weights also improves your body’s hormonal environment, often dramatically. Studies have shown that resistance training, either on its own or as an addition to endurance training, can raise testosterone by as much as 50 percent, while also lowering levels of cortisol, the stress hormone.

Strength Training Will Make You a Better Athlete

Let’s start with the obvious: strength training makes you stronger. How much stronger? If resistance training can increase your muscle mass by 50 percent, you might think that strength would also go up by 50 percent, but you’d be wrong. Strength depends not only on sheer muscle mass, but also neurological and technique factors. Advanced trainees are typically two to three times as strong as novice trainees of a similar weight. This has obvious carryover into athletic pursuits, including obstacle racing: a competitor who lifts weights will be at a huge advantage for challenges like climbing, traversing monkey bars, and pulling heavy objects.

Start Strength Training Today. Download the Spartan Bodyweight Workout Plan.

A common objection to strength training is that it reduces mobility and flexibility—in common parlance, that it will make you “muscle-bound.” While this does happen with bodybuilders who use steroids to become unnaturally huge, studies have shown that resistance training does not reduce flexibility in healthy young people and actually improved flexibility in the elderly.

Mobility is defined a bit differently than flexibility: it’s not just your range of motion, but your ability to exert force throughout that range of motion. In other words, mobility is the combination of strength and flexibility. This makes intuitive sense—senior citizens who need to use a walker aren’t very mobile, even if they are flexible. By that definition, strength training clearly improves mobility even more than it improves flexibility.

The other concern many athletes have is that strength training will reduce their endurance, or vice versa. Like the “muscle-bound” concern, there’s a grain of truth to this. Some of the muscular adaptations involved in strength and endurance training are mutually exclusive. However, this is only a major factor when taken to an extreme, and when you focus exclusively on lifting the heaviest possible weights. You shouldn’t try to become an elite powerlifter if you want to be a good marathon runner, but moderate amounts of resistance training—say, two or three sessions per week—won’t have much impact on endurance, particularly if you train with lighter weights and higher numbers of repetitions, and it will actually improve your performance in endurance events that include strength and power components, like Spartan races.

Strength Training Will Make You Healthier

We’ve established that lifting weights will get you into shape, make you a better athlete, improve your overall well-being, and maybe even improve your sex life. But what does it do for your health? As it turns out, lifting weights is one of the fundamentals of a healthy life.

Let’s start with cardiovascular health. A 2017 meta-analysis (a study that synthesizes a bunch of other studies) concluded that resistance training has similar cardiovascular benefits to aerobic training alone, and combining resistance and aerobic training is better than either one on its own.

How about injury risk? Another meta-analysis concluded that resistance training improves bone density, lowers the risk of fractures, and improves multiple risk factors for osteoporosis, to a greater degree than aerobic training.

Of course, the ultimate measure of health is life expectancy, and by that measure, strength training is practically the fountain of youth. One study found that among senior citizens, strength training was associated with a 46 percent reduction in all-causes mortality, meaning that people who lift weights were 46 percent less likely to die during the study compared to those who didn’t.

Get Started on the Path to Strength

You don’t need to start hitting the gym five times a week, and you don’t need to lift heavy. As an endurance athlete, you’ll probably respond better to lighter weights anyway. You also don’t need to use every piece of equipment in the gym—just six to 10 compound movements are plenty to start with. Here are two workouts you can use for your first two months.

Workout 1

1. Deadlift, three sets of 8–12
2. Bench press, three sets of 8–10
3. Barbell or cable row, three sets of 12–15

Workout 2

1. Barbell squat, three sets of 8–10
2. Chin-ups, three sets of 10–12, or to fatigue if using body weight
3. Military press, three sets of 12–15

Alternate between these two workouts, hitting the gym two or three ways a week and resting two or three minutes between sets. Before long, you’ll be turning some of that extra body fat into muscle, strengthening your bones, and improving your race time.

And yeah, you’ll also look good.

Want more training help? Download the Spartan Training Plan.