Advanced sit up variations to target different parts of the abdominals and hip flexors. These sit ups are hard but amazingly effective!
Sit ups tend to be both overrated and underrated: some people never do them, whereas some people do nothing but sit ups for their core.
The truth is always in the middle. Sit up is an EXCELLENT exercise, but it alone won't maximize your core development. Treat it as a part of your workout and you will get the best results.
One less known aspect of the sit up is that it's not just an exercise for abdominals. Sit up is also a fantastic exercise to target the muscles that flex the hip (hip flexors).
When targeting the hip flexors, the sit up form is just very different because you are purely focusing on hip flexion and not abdominals.
Here are great advanced variations of the sit up to target different parts of the abs (upper and lower fibers) and different hip flexors (inner and outer).
Sit up workout can consist of total of 10 sets of different sit ups between 5-15 repetitions each. In the beginning it's crucial to just master the basic sit up where both hip flexors and abdominals are working hard. These are for advanced only!
For complete core training (abdominals and obliques), we recommend to check out Abs 20XX. It's a guide about developing the core and combining it with the proper diet.
Sit Up Crunch

In the sit up crunch you keep your hips locked and focus only on crunching from the abs above the pelvis.
The movement of your hips should be minimal or nonexistent. You are doing a basic crunch while stabilizing the hips.
The exercise can be modified to target different parts of the abs. You can do a small crunch with the upper part of your abs to target the upper abs, or a bigger crunch which targets both lower and upper fibers.
Sit up crunch is an advanced variation of the crunch because not only is the range of motion bigger, there is also the stabilizing element of the lower abs. This makes the sit up crunch one of the most intense abdominal exercises out there.
Start slowly, focus on controlled repetitions and don't over arch. How much you arch your back will depend on your lower back strength -- arch too much and it can be dangerous.
Hip Flexor Sit Up

Hip flexor sit up is designed to hit the hip flexors (quadriceps and upper thigh muscles). Your abs will get worked but their only purpose is to stabilize and keep the core stiff and tight.
In the hip flexor sit up there is no crunching motion at all: the core is stiff as a board. Instead you focus 100% on flexing from the hips and bending from the pelvis.
Surprisingly, hip flexor sit up is one of the best exercises to really hit the hip flexors. Especially because there is no high requirements for flexibility or mobility.
You can target different hip flexors by changing the rotation of your legs:
- Knees pointing outwards (external rotation) will target the groin area and adductors.
- Knees pointing inwards (internal rotation) emphasizes outer hip flexors such as the tensor fascia latae (TFL) and quadriceps like the rectus femoris.
Mind-muscle connection is super important here. If you have trouble feeling the hip flexors working, then you should first build sufficient levels of strength with the basic sit up.
Single Leg Sit Up

Single leg sit up is one of the most advanced variations of the sit up and will allow you to work the hip flexors on one side at the time. Your obliques may also get worked.
Just because you can possibly complete the single leg sit up, doesn't mean you are fully ready for it.
Too much intensity too soon will create a bad and less effective form. For this reason, the two-leg hip flexor sit ups are your best friends in the beginning and they should never get old anyway.
Single leg sit up is phenomenal as a part of your core/leg workout if you are strong enough to do it. What I like to do is to start with 2-3 sets of single leg sit ups and then finish the workout with 5-6 sets of two-leg sit ups.
Form is king - not repetitions. Focus on slow and controlled execution where you feel the targeted muscles (hip flexors) working and firing.