Is it Safe to Work Out Twice a Day?

Most of us have a hard-enough time fitting in one workout per day. But, bizarrely enough, that’s one reason why two-a-days—performing two workouts between sun-up and sun-down—should be incredibly alluring.

“Two-a-day workouts can be more convenient to fit into a schedule,” says Nicholas M. Licameli, a New Jersey-based physical therapist. He explains that, for people who already have a good base level of fitness, meaning they have to go harder, longer to continue seeing results, two-a-days are one way to do that without completely disrupting the rest of their day. “Instead of struggling to cram in a two-hour training session before or after work," he explains, "two-a-days allow you to train for half the time spread across two workouts."

Or, let’s say, you’re training for a multi-sport event like a triathlon. “You have to build endurance in three different events, and you may have to improve your technique in at least one of them,” explains certified strength and conditioning specialist Lou Schuler, author of Strong. “If you’re competing at a high level, you’re probably doing some strength training as well. I don’t see how anyone could accomplish all that with single daily workouts.” The same holds true if you’re training for an obstacle course race or CrossFit competition.

Apart from requiring a huge time commitment, super-long workouts can often result in the second half of said workout being, well, subpar. As muscles fatigue, exercise byproducts build up, energy (in the form of ATP) levels drop, and both blood sugar and glycogen levels diminish. Physiologically, the body just isn’t able to put forth a maximal effort. However, by splitting up your workouts into two separate sessions—the further apart, the better—your body gets in a mini recovery period, so you can hit your next workout relatively fresh.

What’s more, some research suggests that divvying up your workouts may actually help you get more out of every minute spent sweating. For example, in one European Journal of Applied Physiology study, when young men spent ten minutes cycling, three times over the course of three-plus hours, they reaped greater cardiovascular benefits than those who knocked out all 30 minutes at once. That was true even after matching their cycling workouts for intensity (meaning the guys who broke up their workouts weren’t just working harder).

However, breaking up a 30-minute workout is a lot different than breaking up a two-hour one. That’s especially true if your daily workouts aren’t anywhere near two-hours long. Remember, every exercise session stresses your body. It’s only when rest and recovery is appropriate that the body is able to adapt from that stress to become fitter, stronger, faster—or whatever you’re training toward.

“A 110 percent mentality can quickly run an athlete, let alone an everyday exerciser or weekend warrior, into the ground,” says Allison Tenney, a Florida-based certified strength and conditioning specialist, soccer coach, and former Division I college soccer player. For example, if you’re just getting back into the gym after a workout hiatus and opt for two-a-days, you may simply be stressing your entire body—including your musculoskeletal, neurological, endocrine, and immune systems—way more than it’s equipped to handle. Exercise performance backslides, results putter out, inflammation gets out of hand, workouts feel like a drag, injuries flare up, and yeah, things just suck.

“Two-a-day workouts, if not properly programmed and implemented, can increase the of overtraining injuries as well as physical and mental burnout,” Licameli adds.

That “properly programmed and implemented” part is huge and, ultimately, it determines if your two-a-days work for or against your goals. Here are some guidelines to max out your results with daily doubles—without winding up injured, burnt out, or just hating the gym.

Pair Different Exercise Intensities
Two-a-day workouts, which have their roots in offseason and pre-season athletic training, typically aren’t meant to hammer the body all day long, Tenney says. For example, when performing two-a-days, soccer teams usually aren’t running suicides during both workouts. Yeah, they might run suicides in the morning, but come evening, they are practicing ball-handling drills and performing mobility exercises.

“For maximal gains with double days, you have to make sure that you’re pairing workouts in a way that won’t overload a single system,” she says. Without getting too science-y, you’ve got your anaerobic energy systems (phosphagen and glycolytic) and aerobic one (oxidative), and each is responsible for supplying your body with the ATP it needs to meet the demands of each workout.

The easiest way to keep from overtaxing one of them is to vary your intensity from one workout to the next. For example, instead of performing two heavy strength workouts, you could hit the weights in the morning and then perform light to moderate cardio in the evening, she says. And yes, you typically want to make your first workout the most intense one. That way, when you go to really challenge your body, you’re firing on all cylinders.

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Mix-and-Match Body Parts
All energy systems aside, it’s also important that you don’t spend so much time working one body part or muscle group that it turns to mush. Your ideal strength strategy: body-part splits, explains personal trainer and online physique coach Bryan Krahn. For example, if you work your chest in the morning, you could work your quads in the evening. You could also train your biceps in the morning and triceps in the evening. You get the idea.

However, Krahn does add that, if you have a muscle imbalance or weak spot that you want to shore up, training the same body part twice per day, twice per week, can help its muscles catch up. He explains that morning workouts would focus on higher-intensity strength sets, using heavy weights that you can move for somewhere between four and eight reps (depending on the move, your goals, and strength training background). Evening workouts would involve lower-intensity, more endurance-focused sets, using lighter weights that you can move anywhere from 12 to 20 reps. To avoid overtraining, for every two to three weeks in which you consistently train a body part twice per day, schedule one week in which you only train that body part only once per day, he says.

Increase—And Track—Your Recovery
“With increased training volume and frequency, comes a greater need for proper physical and mental recovery,” Licameli says. To ensure you’re getting the right amount of recovery, given your fitness, workouts, and overall lifestyle stressors, he recommends tracking. “Ways to measure your recovery include extent and duration of muscle soreness, levels of fatigue, resting heart rate [big jumps point to overtraining], mood, and overall performance.”

Meanwhile, Tenney has found a lot of success with tracking heart rate variability (HRV). The differences in the amount of time that passes between heartbeats, HRV can clue you in to your body’s overall stress levels, with research linking decreased HRV to increased inflammation and overtraining. HRV apps such as ithlete can track yours while giving recommendations on when you need to schedule in an extra recovery day.

Eat to Fuel Both Workouts
Your exact nutritional needs depend on your training routine and goals, but when you increase the amount of time you spend working out, you have to increase the amount of nutrition you take in.

“Pad the workout,” says registered dietitian Jim White, spokesperson for the Academy of Nutrition and Dietetics. He recommends planning your meals and snacks so that you eat about an hour and a half before each workout and about one hour after each workout. These meals should be rich in liquids (water over everything else) and foods that are rich in carbs, protein, and electrolytes such as potassium, he says.

These pre- and post-workout meals and snacks will have the double purpose of increasing your daily caloric intake, he says. Fortunately, says board-certified sports dietitian Georgie Fear, the bulk of your extra calories should come from high-quality, whole carbohydrates and then protein. Together, they will fuel your workouts while keeping you building, rather than burning, muscle.

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