No matter how unappealing you may find the prospect of a tough cardio day, you also know that tough cardio days are really, really good for you. They get the sweat flowing, they’re good for your heart, and each one is a great opportunity to catch up on your podcast queue. But there is a possible downside to cardio, though, that has nothing to do with your feelings about doing it: It can burn muscle in addition to burning fat, and muscle is usually not something most gym enthusiasts are keen on sacrificing.
Chris Hinshaw, Reebok athlete and the founder of Aerobic Capacity in Cookeville, Tennessee, has long helped numerous CrossFit champions—Mat Fraser and Rich Froning, to name just a few—learn how to strike this exact balance in their quests to become the Fittest Man on Earth. To ensure that your diligent cardio workouts don’t impact your diligent efforts to move more weight around, we asked him to share a few of his tips. Whether they propel you to an appearance in the next CrossFit Games, of course, is entirely up to you.
If you’re interested in dropping a few pounds before beach season hits, don’t eliminate your strength training days altogether and replace them with extended cardio sessions. Keep splitting your time fairly evenly between the two—two to three days per week of each—and be sure that in both settings, you don’t allow your body to get used to anything. Cardio and strength training activities come in all shapes and sizes, and if yours consist of identical five-mile runs and identical 45-minute weight room sessions, you’re doing it wrong. Relying too heavily on one type of exercise will cause you to miss some muscle groups you should be hitting harder.
“Running is great, but if you only run, you’re using the same muscles over and over and over again, and while those muscles may be strengthened, a lot of other muscle groups get completely ignored,” explains Hinshaw. Try substituting your next treadmill session for a lap swim, or skip heavy bench day in favor of a high-intensity circuit workout.
Sorry, reluctant pavement-pounders: To preserve the fruits of your strength training labor, your cardio regimen should include at least some running. Why? “When you run, you have to support your body weight,” Hinshaw explains. “On a rower, a stationary bike, or in the pool, your body is supported by an object or by the water itself. If you run and develop a higher level of comfort supporting your own structure, that strength will carry over.” It’s the secret fitness two-for-one you can’t miss out on.
Fasted cardio—running on an empty stomach—can be a great way to burn fat. Once the fat runs out, however, the body taps its our protein stores in the form of muscle mass, which limits the amount left to repair and build new muscle tissue. When you're trying to get stronger, this is not an ideal situation. To prevent your body from eating away at itself, think about getting some fuel in your body first. That can mean eating before a morning workout, for example, or moving your workouts to the afternoon or evening, when you’ve had the chance to store up some energy during the day.
Whatever form your cardio takes, don’t do it at the same speed and intensity until the timer finally hits 60 minutes. “You want the entire spectrum of muscle fibers to be developed during your workouts,” explains Hinshaw. “If you only stick with one speed, your body will only know how to run at that speed, and all the fibers you’re neglecting won’t be available to you anymore.”
Executing on this tip just requires a little creativity. If you’re running twice a week, dedicate one of those days to interval training and the other to a longer, steady-paced run. If you’re on the bike, mix in some hill sprints with your longer trips. By choosing cardio that also encourages strength-building, you’ll minimize the chances of the sort of weight loss you don’t want.
If you’re ready to fine-tune a cardio regimen but aren’t sure where to start, give Hinshaw’s three-day running program a shot. On the first day, try a ten-minute treadmill workout in which you do an all-out sprint for five seconds, every minute on the minute, and then back off to a recovery pace for the rest of it. (Yes, that’s a ten-minute workout. If you’re honest about the all-out sprint, trust us—it will be enough.)
On the second day, go for a more conventional long run at 10K or half-marathon pace—whatever those terms mean for you. Finally, on the third day, try a 25-minute interval workout: a minute-long warm-up, followed by four periods of equal work-to-rest ratios. Three minutes of sprinting and three minutes at a recovery pace, for example, is a good place to start.
“The high-intensity interval workout will develop fast-twitch muscle fibers and create fatigue,” says Hinshaw. “The slower, more steady-state cardio will challenge slow-twitch recovery fibers. You’re working both ends of the spectrum and no longer neglecting any muscle groups.” And you can do all of it without having to worry that those hard-earned gains are quietly going to waste.
