As soon as people find out that I'm a trainer, they decide it's time to play 21 questions. I get asked a variety of things, like what I eat, how I train, what I think about trendy diets, how to get stronger arms, and the list goes on.
Another question I get asked a lot is if I think it's bad to work out twice a day. Technically speaking, no, it's not bad and you won't get in trouble, but I don't advise it for the general population. Why? First and foremost, I think it's possible for you to achieve whatever goal you may have by working out smart and once per day.
My second reason is because I don't think people do enough when it comes to recovery and nutrition in order for the body to perform well and sustain two-a-days. Yes, physically it can be done, but without eating enough to fuel your body and doing necessary recovery work to keep your body performing at a high level, the two-a-days will only lead to burnout, fatigue, and injury.
With that being said, in my opinion, there are two exceptions to doing two-a-days. The first is that you're either a collegiate or professional athlete. This is because essentially your job is to perform at the best of your ability. Not to mention, these athletes have access to world-class facilities, doctors, dietitians, physical therapists, and coaches who all have the same goal of keeping the athlete as healthy as possible while maintaining a high performance level. The other exception is if you're doing one intense workout paired with some form of a recovery workout like yoga. In my opinion, this is fine because you aren't putting too much stress on your body.
Instead of doing two-a-days, I think you can get in shape and stay strong working out once a day. For example, you can do an intense strength training session on Monday, followed by a fun Spin class on Tuesday, rest on Wednesday, and so on. So to answer the question, if your recovery game and nutrition aren't on point, you more than likely shouldn't work out twice in a single day. Instead, I recommended creating a weekly workout plan (or asking a trainer to make one for you) so that you feel more prepared and can get the most out of your workouts.
If you're looking for something more long-term, get started with this four-week workout plan to get back in shape and build muscle.