Does It Matter If You Do Weights or Cardio First?

One of the first questions we ask ourselves when we arrive at the gym is: cardio or weights? There are countless machines built for running, squatting, cycling, and lifting, yet no directions on the workout that’s best to tackle first. As a result, many of us simply order our exercises in the sequence that feels most enjoyable—or based on the equipment that’s currently available, without really considering whether we might be hindering our results in the process.

According to some fitness experts, it’s a common misconception that cardio should kick off a workout because jogging or cycling is considered a necessary “warm-up.” In fact, aerobic training (cardio) may make a weightlifting session feel harder, because it fatigues the fibers of your muscles, so once you reach for the weights, your form and endurance could suffer. In a study published in the Journal of Strength and Conditioning Research, researchers found that exercisers did fewer weightlifting reps if they did cardio first.

What’s more, starting with dumbbells can actually boost your fat burn. “I always recommend doing weights before cardio,” says Los Angeles-based trainer Jennifer Purdie, NASM-CPT. “This order ensures you can have the most efficient workout. You’ll be strong for the lifting and use glycogen fuel for energy. Once you burn off your glycogen fuel, your body will shift to burning fat. You could burn more fat in your cardio session this way.”

In layman’s terms, pumping iron will burn through your anaerobic energy, which means exercise without oxygen (as in, not cardio). After you complete all of those reps, your cardio will rely on burning fat for energy. This sequence of muscle-building weightlifting followed by fat-burning cardio will leave you with the most noticeable physical results.

For those who need to focus primarily on aerobic fitness, it is still advisable to incorporate some resistance work. “If you’re training for a marathon or an event that requires significant amounts of cardio, I recommend doing weightlifting on different days,” Purdie says. “You want to be as strong as possible for weight-lifting sessions because you actually burn more calories after weightlifting than with cardio, as your body works harder to repair itself.” Check out these signs that it’s time to switch up your workout.