Crunches alone won't give you a comprehensive core workout. You need to do a range of exercises and movement patterns to work all of your core muscles in a range of ways.
Wondering where to start? Grab a pair of light dumbbells and give this six-move session from Sweat app trainer Britany Williams a go.
It features several rotating and load-bearing moves that will provide a comprehensive workout for your mid-body muscles.
Watch Britany Williams' abs workout
Perform the exercises as a circuit, completing 12 repetitions of each (or eight on each side, if it's a one-sided movement). Williams advises running through this six-move sequence two times in total, or three if you want an extra challenge.
Why you should swap sit-ups for these exercises
Why ditch sit-ups and crunches in favor of this alternative abs workout? Because "abs exercises with twists and holds can help you better target all aspects of your core," Williams says.
Both sit-ups and crunches focus on flexing (or bending the spine), which will primarily target your rectus abdominis—the muscles on the front of the stomach, responsible for the six-pack shape.
But there's much more to the core than this. It's actually made up of a wide collection of mid-body muscles, which provide stability and spinal support. These muscles are also responsible for transferring power between your upper and lower body, so strengthening them could improve your sporting performance and make everyday movements easier.
Williams' routine provides a comprehensive core workout, rather than just focusing on the rectus abdominis. The rotational movements she includes will target the internal and external obliques, which run down the side of the abdomen. She also targets the spine-supporting transverse abdominis muscle, by using exercises that require you to hold your trunk steady against the weight of your own body (such as the plank variations) or a heavy dumbbell (see the overhead dumbbell marches).
If you don't have any weights at home, you can do this workout with a pair of filled water bottles (as long as they weigh approximately the same).
Or, if you want to add some to your home workout set-up, take a look at our guide to the best adjustable dumbbells, tried and tested by our team of fitness writers.