July 11, 2026, 4:02 pm | Read time: 3 minutes
A classic among abdominal exercises: the sit-up. Recently, a personal trainer told me that many people don’t know how to distinguish them from another abdominal classic, the crunch. The two exercises are even confused. This often leads to a misjudgment of the difficulty level of sit-ups. Even though beginners at the gym may have heard or read about sit-ups, the exercise is not ideally suited for them. Find out why at FITBOOK.
For crunches and sit-ups, you don’t need much: just a mat so you don’t have to do them on a hard surface. That’s why this bodyweight exercise has been popular for decades to shape the abs. There are more effective ways to achieve the dream six-pack, but crunches and sit-ups certainly have their place.
As part of a diverse workout routine, they isolate the straight abdominal muscles and help define them—if done correctly. Sit-ups, in particular, pose an unexpected challenge for beginners because they look simple but are often performed incorrectly, rendering them almost ineffective.
Difference Between Crunches and Sit-ups
The names of the exercises already provide good clues about the central difference. In a crunch (abdominal press), you move your upper body toward your bent knees with a tense abdomen (you may have heard the expression “pull your belly button inward”). You essentially press the abdominal muscles together. Only the shoulders and, at most, the upper back lift off the ground. The lower back remains on the mat.
The sit-up (sit-up) is different. Here, you move from a lying position to an upright sitting posture, meaning you must lift your back completely off the ground.
Why Sit-ups Aren’t the First Choice for Beginners
Both exercises should be performed in a controlled, slow manner without momentum. Only when the movement is purely driven by the abdominal muscles do they effectively train them. Using momentum primarily engages the pelvic muscles, which is not helpful if you aim to tighten your abs.
With proper technique, sit-ups become particularly challenging. To perform them correctly (without momentum), you need a strong core. You may have seen in the gym the variation where someone holds the feet of the person doing sit-ups. This assistance can help the exerciser focus entirely on their upper body. However, it is ineffective if used to simply swing into a sitting position. While the exercise may look correct and impressive to novices, it doesn’t train the abdominal muscles.
Crunches are clearly the smarter choice for beginners because they require less from the abdominal muscles. They are a good starting point for abdominal training. Additionally, incorporating exercises like leg raises or squats (where the abdominal muscles are needed for stabilization) can gradually strengthen the core, making sit-ups a manageable challenge.