Here’s a question that I get a lot: Is there a best time to train your abs in a workout?
The answer is yes.
First, consider that your abs work constantly - even when you’re engaging other muscles. Your abs fire while doing everything from squats to sprints to shoulder presses and so on. The core works to keep you stabilized and properly supported. Even when walking down the street, you’re using your abs.
Because your abdominal muscles are so important and because they assist in so many movements, it’s best to train your abs the end of your workout session.
If you train your abs at the start of your workout, on the other hand, they could become fatigued - and subsequent exercises may suffer. If your abs can’t assist in a dead lift, for example, you may be unable to lift as much weight. Or, even worse, your form may become compromised and injury could result. In situations like these, fatigued ab muscles can become a limiting factor for non-ab exercises - thereby hampering progress and results.
The bottom line: Save crunches, sit-ups and the like for the end of your workout session. Doing this ensures best results on non-abdominal exercises that require core support.