Sit-ups remain one of the best known exercises for people trying to strengthen their abdominal muscles, but they may not work the core as effectively as many gym users believe, according to a strength and conditioning academic.
Dr Lee Brown, senior lecturer in strength and conditioning at the University of East London, said the familiar movement is often treated as the standard route to stronger abs because of its long association with boxing gyms, films and fitness routines. In practice, he said, it is not the most targeted exercise for the muscles many people are trying to train.
A sit-up is usually performed by lying on the back with the knees bent, lifting the upper body towards the thighs, then lowering it again. The abdominal muscles are involved in that movement, but Dr Brown said a significant part of the work comes from the hip flexors. These are muscles at the front of the hips that help lift the legs and bend the body at the hip.
One of the main hip flexor muscles is the psoas major, a deep muscle that connects the lower spine to the upper leg. Because it contributes strongly to the sit-up action, the exercise does not isolate the stomach muscles in the way many people expect.
The distinction matters because core strength is not only about appearance. The core includes muscles around the abdomen, sides, lower back and pelvis. These muscles help the body stay stable during everyday movement, including lifting, carrying, walking, climbing stairs and getting up from a chair.
For people exercising at home or returning to fitness after a break, assuming that more sit-ups automatically means better core strength can be misleading. It may also encourage people to repeat the same movement many times, rather than building strength and control across a wider range of muscles.
Dr Brown said doing too many sit-ups can contribute to lower back problems in some people. He said overworking the hip flexors may make them tight and stiff, which can affect posture and create an imbalance around the pelvis and lower back.
That does not mean every sit-up is harmful, or that everyone must avoid them. The concern is mainly about relying on them as the main abdominal exercise, especially when they are performed in high numbers or with poor control. People who already have back pain, recent injuries or medical concerns should seek guidance from an appropriate health or fitness professional before changing their exercise routine.
Dr Brown pointed to several alternatives that may train the core more effectively by requiring the body to resist movement and stay stable. These include planks, side planks, farmer’s carries, suitcase carries and bird dogs.
A plank involves holding the body in a straight line while supported on the forearms or hands and toes. It challenges the abdominal muscles, back, shoulders and hips to work together to maintain position. A side plank uses a similar idea while lying on one side, placing more emphasis on the muscles along the side of the trunk.
Farmer’s carries involve walking while holding a heavy weight in each hand, while suitcase carries use a weight on one side only. The body has to resist leaning or twisting, which helps train stability through the trunk. These movements are commonly used in strength training because they are close to practical daily tasks, such as carrying shopping bags or luggage.
Bird dogs are usually performed on hands and knees, lifting the opposite arm and leg while keeping the body steady. The exercise is often used to build control through the back, abdomen and hips without repeatedly bending the spine.
Dr Brown also said Pilates and yoga can help develop core strength. Both forms of exercise often focus on control, posture, breathing and stability, rather than repeated bending movements. As with any activity, the benefit depends on how exercises are performed and whether they are suitable for the individual.
The message for the public is not that one exercise will produce visible abdominal muscles on its own. Body shape, overall training, diet, genetics and body fat levels all affect how the abdominal area looks. Core training can improve strength and control, but it should be viewed as part of a wider approach to physical activity rather than a quick fix.
For now, sit-ups remain a familiar part of many workouts, but experts increasingly recommend a broader approach to core exercise. People who want to strengthen their midsection may benefit from including stability based movements and carrying exercises, while being cautious about repeated sit-ups if they cause discomfort or aggravate existing back symptoms.
