Trainers explain why there isn't a magic formula when it comes to doing cardio or weights first.
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Like many people, you probably face this constant conundrum when you walk into the gym: Should you do your cardio or weight lifting first? The short answer is that it largely depends on your goals.

"For example, if you're training for a marathon or any long-distance run, I would prioritize your run before strength training so you can focus on that without the distraction of your legs being fatigued," says ACE- and NASM-certified Apple Fitness+ trainer Betina Gozo. On the other hand, if your goal is to build stronger glutes, you might want to hit the squat rack before the treadmill. "There's so much more muscle recruitment needed in strength training, so you would want to save all the energy you can for it," says Gozo.

Even if you don't have a super-specific goal and want to train for better overall fitness, it's important to combine cardio and strength wisely so you don't overwork the same muscle groups. Focusing on the same muscle groups during back-to-back cardio and strength training sessions doesn't allow for adequate recovery, according to the American College of Sports Medicine. Plus, it could lead to fatigue and poor performance, thus increasing your risk of injury. So it's important to carefully consider the type of exercises you're doing when debating whether to do cardio or weights first.

Here, top trainers and exercise science experts break down when you should do cardio before weights and when the opposite is more beneficial. (Related: Shape Studio: Dance Cardio Core Workout)

When to Lift Weights Before Cardio

If you have a specific strength goal — such as, you're looking to PR on your deadlifts or perfect the Turkish get-up — you definitely want to make the weight room your first stop. (Related: The Perfect Strength Training Workout for Beginners)

Here's why: Your muscles are like a rubber band — they need to be taut enough to restrict whatever they're wrapped around, explains Gerren Liles, an ACE-certified Hyperwear athlete and Equinox master trainer. "If you take the rubber band and repeatedly pull it, it becomes too loose and unable to hold objects together. Your muscles work the same way," says Liles. "The repetitive movements in cardio reduce your muscles' ability to contract effectively, leaving you disadvantaged if you're doing pure strength training and lifting for maximal effort right afterward."

Science backs up the weights-before-cardio plan. A 2016 study published in the Journal of Strength and Conditioning Research recruited 11 healthy and fit men and examined their strength performance 10 minutes after a vigorous aerobic endurance workout. They were tasked with running on a treadmill at moderately hard, very hard, or maximal intensity for between 20 and 45 minutes, then performing resistance exercises like the high pull, squat, bench press, deadlift, and push press. These strength exercises were performed for 3 sets of 6 to 10 reps at 70 to 80 percent of their 1-rep max, with a three-minute rest interval between sets.

Results showed that their performance on the strength moves was significantly compromised after the aerobic workouts. Participants performed fewer reps with the squats, in particular, and power was reduced for the high pull, squat, and bench press after doing most of the aerobic workouts.

Moreover, a November 2016 study published in the European Journal of Sport Science had 30 recreationally fit men complete four different training protocols: strength training, strength followed by endurance training, endurance followed by strength training, and no training. The results suggest that performing endurance exercises prior to strength training results in impaired strength training performance, especially when lifting heavy. The study also showed that 1-rep maximum performance was much better during strength training alone and during strength training before endurance than in the reverse order.

Doing cardio after strength training may have a bonus benefit as well, according to Pete McCall, C.S.C.S., host of the podcast All About Fitness. Muscle cells store something called glycogen, which fuels muscular contractions, explains McCall. Glycogen is made from carbohydrates that your body breaks down into fuel. When your body converts glycogen into energy it becomes adenosine triphosphate, otherwise known as ATP. This process produces byproducts that can be recycled back into ATP and used as energy, explains McCall. Interestingly enough, your body uses glycogen as fuel during higher-intensity exercise such as lifting weights, and creates these byproducts which can actually be used as fuel for lower-intensity activities such as steady-state cardio, he says. Cool, right?

When to Do Cardio Before Weights

As mentioned, if you're training for a big endurance event, such as a triathlon or marathon, you generally want to use your energy for your cardio efforts and focus on them before you hit the weights.

Even if you're not focusing on a cardio-specific goal, there are some instances when squeezing in some cardio before strength work can be beneficial — namely, as a warm-up. "Doing cardio before strength can be an effective strategy for ensuring the body is properly warmed up and prepared for the challenges of the strength exercises," says McCall. "Doing some light, steady-state cardio — about 10 minutes — before any intense effort or activity prepares the body for exercise or performance," says Eric Sternlicht, Ph.D., associate professor of health sciences at Chapman University in Orange, California.

If you have a specific strength-related goal, such as deadlifting a certain amount of weight or learning a specific technique (e.g. an Olympic lift or kettlebell move), keeping it low-intensity is key. You should steer clear of HIIT and instead opt for steady-state cardio to limit the risk of fatigue affecting your strength workouts, says McCall.

A 2013 study published in the Journal of Strength and Conditioning Research agrees, finding that when exercisers did a low-intensity warm-up for 15 minutes, they were able to lift more weight in a 1-rep max test on the leg press machine than those who did no warm-up, only warmed up for 5 minutes, or did a moderate-intensity warm-up of any length. (Related: The Dynamic Warm-Up for Weight Lifting That Will Improve Your Performance)

However, if you're just strength training for general fitness, you can go a little harder with your pre-weight lifting cardio. "If someone is doing strength training for general fitness — meaning no specific goals — doing steady-state or aerobic intervals for 15 to 25 minutes or a short HIIT session of five to eight minutes would be okay before strength training," says McCall.

What If Your Goal Is to Lose Weight?

When it comes to weight loss, it doesn't really matter whether you do cardio or weights first — but strength trumps cardio in terms of general importance, says Strenlicht. Most people will focus on doing more cardio when they're trying to lose weight because it burns more calories, but it's far better to do strength training two to three days a week, he says.

Why? Strength training helps you increase or maintain lean body mass, which will burn more calories in the long run. ICYDK, the more muscle mass you have, the higher your resting metabolic rate (the minimum amount of calories your body needs to perform normal bodily functions), explains Sternlicht. And when you do heavy weight training with shorter rest intervals, you produce greater excess post-exercise oxygen consumption (EPOC), which are the calories you burn long after your workout. That's because it demands more on the anaerobic (oxygenless) energy pathways during exercise, which increases the need for oxygen post-workout. So the more intense your lifts are — and the less rest you take between sets — the more EPOC you'll produce.

That said, you shouldn't skip cardio altogether. "Ultimately, you use more energy and expend more calories doing aerobic training because you're moving consistently, whereas, with strength training, you may be using two-thirds of your time recovering, so adding some cardio can increase your overall calorie burn," says Sternlicht.

For that reason, it might be better to do hybrid strength-cardio workouts instead of steady-state cardio, says Gozo. "Each week, I recommend doing two total-body strength workouts with higher reps and lower weight and some interval training in between (such as an Orangetheory or Barry's Bootcamp class), plus two or three heavy strength workouts instead," she says.

If you want to lose weight, it's also important to increase your non-exercise activity thermogenesis (NEAT) — aka any movement or physical activity you do outside the gym, says Sternlicht. "Taking more walks, parking your car farther from the entrance, and walking up the stairs instead of the elevator are all examples of NEAT that will increase your calorie burn," he says. (Related: What Is a Calorie Deficit, and Is It Safe?)

How to Effectively Combine Cardio and Strength

Regardless of whether you do cardio or weights first, you're performing a workout that combines both strength and cardio into one session, aka concurrent training. And, for the general public interested in using exercise to maintain healthy body weight, doing both cardio and strength in the same workout can be effective for expending energy and building muscle without any real risks, says McCall.

In fact, a July 2014 study in the Journal of Strength and Conditioning Research enlisted 23 inactive female college students to follow an eight-week exercise program, which involved either doing endurance before resistance training or resistance before endurance training. The endurance portion consisted of 30 minutes of aerobic exercise at moderate intensity and the resistance portion involved performing 3 sets of 8 to 12 reps of five or six different strength exercises. Researchers found significant improvements in performance, strength, and lean body mass, regardless of exercise order (aka regardless of whether you do cardio or weights first).

In terms of designing a concurrent workout, there isn't a magic formula, according to Sternlicht. "You have to do whatever fits your lifestyle and schedule," he says. Whatever you choose, it's a good idea to mix it up every once in a while. Varying your workouts — whether you alternate doing cardio and strength first throughout the week or stick to one for a couple of weeks and then switch — helps challenge your body in new ways, so you don't hit a fitness plateau, says McCall.

And make sure you don't over-fatigue one muscle group. For example, consider pairing upper-body workouts with HIIT cardio days, and doing lower-intensity steady-state cardio on days when you're doing lower-body strength moves, says McCall. "Because the leg muscles will be working during the strength training, you don't want to kill them with intense cardio." (See also: Here's What a Week of Perfectly Balanced Workouts Looks Like)

The bottom line when wondering if it's better to do cardio or weights first: You want to prioritize your workouts according to your goals. If you're focused on lifting a certain amount of weight or mastering a new kettlebell exercise, then you should definitely hit the weight room first and supplement with some steady-state cardio on the treadmill, rower, or bike. On the other hand, if endurance is your goal, you should save your energy to go the distance and couple the stamina-building workouts with low-weight, high-volume strength training. And if you're aiming to lose weight, you want to do a combination of strength and cardio — with a special emphasis on strength.