Cardio used to be king. That is, until researchers and gym rats alike found that strength workouts come with greater fitness and health gains than do steady-state cardio sweat sessions.

For instance, in one Journal of Sports Science & Medicine study, people who cranked out a 20-minute interval strength workout that included pushups, burpees, squats and lunges burned an average of 15 calories per minute. That's nearly twice as many calories as burned during long runs. Meanwhile, when, in a 2015 Obesity study, Harvard researchers followed 10,500 men for 12 years, they found that those who strength trained gained less abdominal fat, a marker of overall health, compared to those who spent the same amount of time performing traditional cardio workouts.

That's because, while steady-state cardio (think: a 45-minute jog on the treadmill) burns calories not just from fat, but also from muscle, strength workouts build muscle, burn calories even after you leave the gym and still strengthen your heart. After all, your heart is a muscle!

"Without question, lifting weights is the most important thing you can do in the gym for your health," says certified strength and conditioning specialist Brad Schoenfeld, assistant professor in exercise science at Lehman College in New York. "If you can only do one thing, lifting is a must."

But, that doesn't mean cardio is without its benefits – or that it shouldn't have a place in your gym routine, Schoenfeld says. "Performing cardio can give you additional benefits above lifting. Strength and cardiovascular workouts can work synergistically," he says.

Why You Still Need Cardio in Your Routine

First of all, there are the obvious cardio benefits of performing cardio workouts – hence the name "cardio." During cardiovascular workouts like running, cycling or swimming, your heart and lungs have to work faster and harder than they do during strength sessions, meaning they become stronger and more efficient than they would during a given strength workout, Schoenfeld says. In fact, research published in The American Journal of Cardiology pinpointed aerobic exercise as the most efficient form of exercise for improving cardiometabolic health.

What's more, while weight lifting may be more efficient than cardio when it comes to fat loss, performing both types of workouts comes with better results than performing strength training alone. That way, you get a major calorie burn from cardio workouts as well as more muscles and an improved metabolic rate from strength workouts, he says.

But, if you're not too into the dreadmill, and are more focused on strength gains, you can rest assured that a stronger cardiorespiratory system means better strength and muscle gains, says Dean Somerset, an Alberta-based kinesiologist and certified strength and conditioning specialist.

By increasing your muscles' capillary as well mitochondrial density, cardio workouts enhance your body's ability to fuel your muscles with more energy and achieve better workout performance, Schoenfeld says. And better performance means better results. (While capillaries are responsible for delivering nutrients to your muscles and removing waste like carbon dioxide, mitochondria act as your muscle cells' microscopic power plants.)

What's more, after every strength set and workout, your heart, vasculature and lungs – all of which you strengthen during cardio workouts – are largely in charge of helping your body recover for optimal benefits, Somerset says. They replenish your body with energy and deliver oxygen, amino acids and other nutrients to your muscles to help them spring back stronger, he explains.

Strength vs. Cardio: How to Find the Right Balance

"Ideally, you should get some cardio exercise every day," Somerset says. "It can even be 10 minutes going for a brisk walk. You don't have to train for a marathon every day. Just do a daily something." A 2014 Iowa State University study even found that 10 minutes of running per day, and at slow speeds, results in a markedly reduced risk of death from all causes as well as heart disease. The American Heart Association recommends performing 150 minutes of cardio per week in 10- to 60-minute sessions.

Above that, how many workouts and how much time you devote to cardio per week largely depends on your fitness goals and current health, Schoenfeld says. Maybe your main fitness goal is to complete a triathlon, to hit a healthy weight or fight sarcopenia, the loss of muscle, as you age. Maybe your doctor wants you to get your heart rate up more often for better cardiovascular health. Or maybe your heart isn't fit for starting a cardio routine. This is where talking to a trainer and your primary care physician about your health and goals comes into play.

For everyday exercisers and weekend warriors, though, the workout that you most enjoy is going to be the best one for you because you'll stick with it, Somerset says. He notes that research consistently shows that enjoyment is the No. 1 predictor of your ability to stay consistent with, and reap fitness and health gains from, a workout. Maybe that means mixing up your strength workout with a spin class or two per week. Or running for every workout and using strength workouts solely for injury prevention and improving your running performance.