Walk into any gym and you will see someone doing a sit up or crunch. When you hear or say abdominal training most people will think of the sit up as the best ab exercise and a go too. Well this just plain out wrong and not effective, and it can actually be leading to more dysfunction of posture and the system. Now the big caveat with the previous statement is that position of the overall system matters most when it comes to abdominal training.
When the system is not in a balanced or “neutral” state and we perform a sit up or crunch then this can lead to poor training of the rectus abdominis due to poor position of the rib cage and pelvis thus not getting full activation of the muscles. The rectus abdominis is the primary focus when doing a sit-up or crunch it pulls the ribcage into flexion up and towards the knees
Ab Function
The Abdominals are designed as exhalation muscles, meaning that depress the rib cage during the exhalation portion of breathing, they pull the ribs down and into internal rotation allowing the diaphragm to dome and ensure proper respiration. The abdominals also create pressure and stabilize the spine, rotate the upper trunk and are part of all postural movements.
Yes most people want the abs to look good, get a six pack and what not, which is fine…BUT first you need to respect the purpose of the abs. If we do not have proper function of the abs and we train them for looks then we add dysfunction on top of dysfunction. This will lead to postural issues, ankle sprains, shin splints, knee pain, hip pain, lower back issue, all the way up to neck and jaw pain. Yes, the abdominals are that influential.
Position Rules All
Ever perform sit ups for 20 reps and at the end you start to feel the front of the hips getting tight. These are your hip flexors pulling you up off the floor rather than your abs, so are you really training your abs? Most likely not. The hip flexor muscles attach to the lower spine, at the end range of the sit up the hip flexor pulls the lower back and spine off the floor.
This will lead to the hips being out of position which will put more strain on the lower back, so if you get back pain or tightness with sit ups it is time to re-evaluate your ab routine. This extended position of the body leads to lower back extension which will diminish the activation of the abs, so you are not going to get the full ab contraction and strength.
Performance
The obliques run the show for performance and life, they rotate us, help us walk, run you name it they are the most important. The rectus abdominis is just a sagittal plane muscle and moves the body in one direction. So the sit up is not the best performance exercise or even close to it. Rotational and anti rotation exercises are where it's at and where it should be.
So to get the most out of your sit up you need to make sure the position is optimal, so get a full exhale and depress the ribs down and together, get all the air out and feel the sides of the rib cage engage, next posterior tilt your pelvis, scoop the tailbone, you will feel more abs. No, from this position using the obliques and rectus abdominis do a sit up. You will feel way more abs, and at the same time should feel more challenging to pull yourself off the floor. This is your abs doing all the work and not letting other muscles take over.