Reposted from: http://www.fitnessrepublic.com/fitness/10-surprising-facts-about-working-out-twice-a-day.html

Written by: Christian Heftel

Most people think about exercising in terms of how many times they work out per week, but some people want to up the ante and get their heart rate up more than once in a day. Working out twice a day has some potential benefits as well as some potential drawbacks. Here are 10 surprising facts you should know about exercising twice in one day.

1. Two-a-Days Can Be Safe

Some people assume exercising twice a day must be bad or unsafe. But if you do it right, this doesn’t have to be the case. According to John Mandrola MD, “two-a-day workouts can be especially useful, and if used wisely, might lead to safer more effective training.”

2. Rest Is Still Important

If you’re working out multiple times per day, you definitely need to make sure you get enough rest. Obviously, it’s good to give yourself some time between your workouts on any given day (some experts suggest waiting between four and six hours between your exercise sessions), and it is equally important to rest your muscle groups between days. For example, if you do a heavy leg workout one day, then even if you get other exercise sessions in the meantime, you probably don’t want to really tax your legs again before for a couple days.

Make sure you take at least one day completely off each week, and potentially more. Additionally, if you notice that you are growing more fatigued and sore over time, or that your ability to perform is decreasing, you may need to increase your amount of rest.

3. The Order of Exercise Matters

If you’re doing both high-intensity (like HIIT or strength training) and low-intensity exercises (like “regular” cardio), you should do the higher intensity work in your first session. It will likely be easier for you to give your all when you’re still fresh. Then, you can do the more endurance-based exercise later, when you’re tired.