Should You Do Sit Ups at Night?

The last thing you want to do before you hop into bed is work out. But if your day is so busy that that's the only time you have — go for it! But don't limit your before-bed workout just to sit-ups.

Although sit-ups might be part of your training plan, they alone won't burn any fat that's covering up your muscles — even if you do them just before bed. Sit-ups are also not comprehensive in terms of addressing the muscles of your core, so they should be only part of a total core-strengthening program.

Whether you do sit-ups at night or in the morning isn't important. Worry about how you incorporate them in a complete core-training program.

​Read more:​ 21 Sit-Up Variations You Won't Totally Hate

Plan to warm up your body for three to five minutes before any workout, even if you just want to crank out a set or two of sit-ups in the evening. For example, don't just drop to the floor to crunch your abs after vegging out for a few hours in front of your favorite evening television shows.

Do two to three minutes of a dynamic warm-up that gets your blood flowing, such as marching in place or stepping up and down on a riser. Then, perform a few exercises that loosen up the back and the front side of your abdomen, warming up the muscles you plan to work. Options for a sit-up warm-up include about 30 seconds each of:

• Cobra pose
• Cat-Cow stretch
• Plank

Sit-ups primarily target the rectus abdominus muscle, whatever time of day you do them. This muscle is the most superficial muscle of the trunk, meaning that — when you're lean enough — it shows up as a six-pack.

In addition to this muscle, however, sit-ups also use the illiopsoas, or hip flexor, to assist as you lift your torso to your knees. As a result, your lower back tends to arch, leading to back pain, especially if you have relatively weak abs.

If you hook your feet under a bar or have someone hold them down as you do sit-ups, you could also cause stress to the discs of the lumbar spine.

Whenever you do sit-ups, perform them slowly and pay attention to how you draw in your belly with each lift. Rapid sit-ups are more likely to use momentum, and consequently, rely mostly on your hip flexors.

Consider modifying the sit-ups to do partial versions, also known as crunches. Crunches have you lift just your head, neck and shoulders off the floor as you pull your belly button into the spine. They still work the rectus abdominis but minimize use of the hip flexors and are far less stressful on the spine.

A comprehensive core routine, rather than just performing sit-ups, helps make your abdomen and back strong for daily activity, sports performance, good posture and overall health.

A comprehensive routine trains not just the superficial rectus abdominis, but also the deep internal muscles of the abdomen, the obliques and the stabilizing muscles of the lower back. Do this routine at night, or any other time of day that works for your schedule.

Many options for comprehensive core workouts exist. After a warm-up (as described above), an easy-to-do routine that requires no equipment and minimal space could include:

• Front plank
• Side plank
• Crunches
• Bird Dog
• Bicycle crunches

If these moves are brand new to you, start with just a 20- to 30-second hold for each of the planks and do eight to 12 repetitions of the other exercises. More experienced exercisers could hold the planks for up to 1 minute and do two to three sets of the other moves.

​Read more:​ The Best Core Workout Routines

Sit-ups at night, or any other time of day, as your lone strategy won't get you abs of steel. A comprehensive core routine performed three to five times per week, along with at least two total-body strength training per week and almost daily cardio exercise is what helps you create a slim, enviable torso.

Your diet plan also influences the look of your abs. Moderate portions and trade sweets, saturated fat and refined grains for lean proteins, fresh produce and healthy fats from avocados, olive oil and nuts.