Is It Better to Do Your Ab Workout in the Morning or at Night?

Read more: Morning vs. Evening Workouts: What's Best for Your Goals?

Your spine naturally lengthens slightly while you're asleep in a reclined position. That's because the flexible intervertebral discs between your vertebrae compress slightly over the course of a day and decompress at night when you're lying down.

The compression is significant; you might be a full centimeter taller when you wake up in the morning, as compared to when you go to bed, according to HealthBeat from Jamaica Hospital Medical Center.

A lot of popular ab exercises can compress your spine, which can put you at higher risk for back pain. That's especially true if you're doing the repeated flexion of a sit-up or crunch, which puts pressure on your vertebral discs and can cause swelling or a serious injury.

You're most vulnerable in the early morning, right after you wake up, since your discs take in water all night long and expand. Thus, added pressure from an early-morning sit-up has the potential to cause a lot more damage than the same exercise being done in the afternoon.

Read more: 5 Myths About Back Pain, Debunked

Disrupting the circadian rhythm with a late-night ab workout might not be a good idea either. Humans, like most mammals, have an internal clock called a circadian rhythm. It's affected by your sleep schedule, your environment and even your workout schedule.

A June 2019 study in the Contemporary Clinical Trials Communication says that exercise stimulates the sympathetic nervous system (your fight-or-flight response), meaning exercising too close to bedtime can keep you awake.

And on the practical side of things, many people find that if they save their workout for later in the day, the busyness of the day and to-do list items crowd out the time they'd set aside for exercise.

All other factors aside, any ab workout is better than no workout. With a strong core, you build a strong foundation for daily activities.

Everyday motions like bending, turning around, sitting, and standing are benefited by strong ab muscles, as are more intense activities like playing a sport, moving out of your apartment or going on a long bike ride.

Any ab exercise is better than none at all, so don't let the time of day keep you from pursuing stronger abs. Plus, a July 2019 study published in Obesity found that regardless of whether participants exercised in the morning or evening, the strongest predictor of being active was working out at the same time every day.

So if you can only exercise in the morning, find alternative exercises, such as the plank, which can help strengthen your abs and core without flexing your spine. Look for a diverse collection of plank variations to weave into your ab workout routine.

Or if you only have time later in the evening, make sure it's not a super-intense workout, save ample time for a cooldown or meditation and aim to finish at least 1.5 hours before bedtime.

Read more: Why Exercise in the Morning Is More Exhausting Than in Afternoon