It's All About Balance
For starters, while you probably shouldn't be doing two fully intense workouts per day, splitting up your workout — doing half of your workout in the morning and the other half later in the afternoon or evening — is actually a pretty good idea. It helps give your body rest, allowing you to work at your highest level of intensity, LA-based trainer Mike Donavanik, told MensHealth.com.
“Think about it like work. The reason people take breaks or lunch breaks is in an attempt to give their mind and body a rest…so when they get back into their shift — they are hopefully more clear-headed and productive,” he said.
While the exact duration of your workouts depends on your activity level and fitness goals, you can try exercising for 30 minutes in the morning, and then 30 again in the evening. (It's also important to keep in mind that some workouts might take longer for others — for instance, lifting might take longer than straight cardio — so they don't have to be evenly split up.)
“For that 60-90 minutes when you’re going all out, it can be both physically and mentally draining,” he said. By splitting up your exercise, you can be more focused and have greater energy and strength output, he advises.
Another effective way to jam more work into a day is to split you AM and PM sessions by body parts or style of workout. Men's Health Fitness Director Ebenezer Samuel, separates his doubles in that method.
"The way I break it up now is skills/athleticism/conditioning/flexibility in the morning, body part strength split in the evening," he said.
How Your Body Handles Doubles
As you’re raising your heart rate, boosting circulation and blood flow to the muscles, and getting a sweat on, your body undergoes stress and those muscles begin to get tired. But once you’ve finished that first workout, getting a few hours of rest allows your body to recover and bring itself back to homeostasis levels.
“Heart rate, blood flow, hormones — they all start to balance back out, so your body is not in a ‘stressed’ state,” according to Donavanik. In that time, you’re able to reboot for another workout, particularly if you eat a post-workout snack or use a foam roller beforehand.
As an added benefit, if you hit the gym twice a day, your muscles can actually increase in mass and strength over time, according to Dr. Paul Mostoff, Chief of Physical Therapy at the NYC-based All Sports Physical Therapy. “By hitting each muscle twice a day, you literally double the amount of stimulus that your muscle receives. Every time you train, you provide your body with a stimulus, which promotes greater protein synthesis and muscular adaptation,” he said. “So by training twice per day, you're giving your body the signal to ‘grow and get stronger’ twice as often."
What’s more, you may also reap the benefits of Excess Post-Exercise Oxygen Consumption (EPOC), known as the “afterburn effect,” which means your metabolism spikes for the next few hours. With EPOC, you’ll burn more calories in the body. When you’re doing two-a-day workouts, you get that afterburn twice. That doesn't, however, give you an excuse to gorge yourself on mac and cheese balls post-workout; some research indicates that the afterburn effect is relatively small.
Plus, if you have a busy day filled with work and social obligations, splitting your workout in two for a morning energy boost and an evening refresher could be a smart idea. “Any time you work out, hormones kick in to make you more alert and productive in that time. Your body will also fight fatigue for some time after the workout,” said Donavanik.
If you're struggling to get to sleep, your rest might also improve if you work out in the evening, too. “Most people will find it easier to fall asleep because they’re placing a greater demand on their body, so they’ll naturally feel more exhausted and be able to fall asleep easier."
Don't Burn Out
There is, however, one caveat: If you’re not used to training hard and you go right into two-a-day workouts, you might be more sluggish than usual. This can happen even if you’re splitting one workout in half, as your body isn’t used to all that work. Either way, seek guidance from your doctor before diving in.
It's also important to note that you shouldn't just stick to the same workout for every session. There is a chance you could overtrain and burn out, which isn't only counterproductive to your goals but can also be dangerous.
Don't try to jam too many HIIT workouts into a short period of time, for example, and listen to your body when it's telling you enough is enough. Continuing to push yourself beyond your limits is a recipe for disaster.
So should you try out a routine built around two a days? That all depends on your goals, and how much time you can commit to each session. But if you're smart about your rest and recovery when you're not training, anyone can use two-a-day workouts to ramp up their fitness.
“Paying special attention to proper warm-ups, hydration, sleep, nutrition, and giving yourself enough rest between training sessions in the same day (at least 4 to 5 hours), will help avoid the pitfalls of over-training,” said Mostoff.