Sales Popup
Someone purchased a
6 hours ago





Your Cart is Empty

February 11, 2022 8 min read

Crunches are one of the more well-known ab exercises, but they can get old after a while. Also known as reverse crunches, knee ups can be beneficial for building ab strength and stability while giving you some variety to core training.

Abs - Anatomy Muscles

Importance of Core Training 

Your core is home to some of the hardest working muscles in your body. These muscles are not only responsible for helping create a six-pack, but they also contract and assist with movements that require twisting, bending, reaching, pulling, pushing, balancing, and standing. 

Your performance in the gym can rely on and may even be predicted by your core strength, and core stability plays a role in injury prevention and functional movement.  

Strengthening your core muscles can help stabilize your body during almost any kind of movement and helps to protect your spine from injury. They can also contribute to reduced low back pain, which is an increasingly common issue across the globe, and one of the more prevalent reasons individuals may seek medical care. 

For most people, their deep core muscles are not as strong as they should be.

In particular, runners with weak deep core muscles are at an increased risk of developing lower back pain. This pain is a consequence of poor form caused by a weak core. Once you start to slouch when you run, you close down the amount of oxygen going into your lungs. 

The whole system of getting oxygen to muscles and holding yourself upright relies greatly on your core. 

Generally, if you want to improve your functional performance you need to work on your core. Knee ups can be a very important way for you to start doing this.

Muscles Worked by Knee Ups

The term core muscles is thrown around a lot that you may not realize how complex of an area it is. It comprises several different muscles that all contribute to movement such as spinal flexion, extension, bending, and twisting at the torso. 

Rectus Abdominis

More commonly referred to as your “six-pack” muscle, the rectus abdominis is responsible for trunk flexion. Anytime you bend over or do a sit-up, you’re using this muscle.

Knee ups can certainly help you create abdominal hypertrophy and directly load your rectus abdominus, making it a beneficial exercise if you’re working on your beach body. 

You may have heard of upper and lower abs, and although it is technically one muscle being referred to, the upper and lower part of the rectus abdominis can be targeted differently. Knee ups can help target the upper and lower part of this muscle group, helping create a balanced body.   

The rectus abdominis may help you look sculpted, but it also serves important purposes for function as well. 

This muscle helps to stabilize the spine, assists in movement of the pelvis, and can affect your posture. Performing knee ups can help improve your overall function while contributing to a better looking physique. 

Strength training is important for building muscle, but abs aren’t made in the gym; they’re made in the kitchen. To ensure you’re getting enough protein in a day, try Whey-Iso after your workout.

Transverse Abdominis 

One of the innermost muscles in the abdomen is the transverse abdominis. It wraps around the front and side of your trunk and lies underneath the rectus abdominis and the obliques. Its primary responsibilities are to help stabilize your spine and protect your internal organs. 

There are plenty of core exercises that can help strengthen the transverse abdominis, but movement patterns like in knee ups can help activate it even more

Along with the other abdominal muscles, the transverse abdominis helps to support the spine, which may lower your risk of injury. Exercising a deeper muscle like this one helps to build a stronger foundation for your entire body. 

This muscle plays a crucial role in reducing low back pain for short and long-term. 

Low back pain is a global health issue that has affected over 500 million people and is one of the main disabilities individuals may suffer from, as well as one of the main reasons for missing work. Therefore, keeping the muscles that can help prevent this strong can be essential for our quality of life.   


Although not directly targeted, several assisted muscles are recruited to help you perform knee ups. The internal and external obliques are some of them. These muscles are located on the sides of the abdomen and help in twisting at the trunk and bending side-to-side. 

As secondary movers, the obliques assist in the movement pattern of knee ups and help support the spine during any kind of movement. 

Exercising these muscles not only help with overall function, but they can contribute to a slimmer, more defined waistline.

Benefits of Knee Ups 

Core training is important for stabilization and movement of the body, but knee ups can provide benefits that regular sit ups may not be able to. 

  • Less neck strain: A common mistake people make when performing crunches or sit ups is pushing their head up with their hands that are supposed to be used for support. This can put your spine in a curved position and add more strain to your neck. Since you’re lying on your back for knee ups, you are able to avoid this mistake entirely. 
  • Easier on your back: When you perform sit ups, your spine may flex, which can put extra strain on your back. Knee ups help reduce flexion in your spine and can be safer than regular sit ups.  The less your spine flexes, the less force is put on it, making knee ups a potentially safer core exercise than sit ups.
  • Injury Prevention: The core plays an important role in supporting the spine, and without it, you can increase your risk of injury in and outside the gym. Any kind of movement typically relies on the core for help, so keeping it strong can help your body move more efficiently and safely.    
  • Carryover to Olympic lifts: Olympic weightlifters and CrossFitters rely on core stability for heavy, powerful barbell lifts like the snatch and clean and jerk. A strong core helps  increase movement efficiency, balance, and endurance, which is especially important when performing powerful lifts.
  • On your way to a six-pack: Core training alone may not get you a six-pack, but it can definitely help. Knee ups target the upper and lower parts of the rectus abdominis, which is responsible for providing the desired six-pack look many lifters strive for. 

How to Perform Knee Ups

Like most exercises, it is always vital that you use the proper form to get the maximum benefit and to prevent possible injuries. 

The knee up is quite a straightforward exercise that only requires the floor or a bench and some extra space. 

This means that you can do it in your home gym as part of a full home workout. Before you begin, make sure there is enough room around you..

  1. Lie with your back on the floor or a flat bench with your feet planted and knees bent.
  2. Put your hands behind your head or at your sides. 
  3. Engage your core by drawing in your navel and contracting your abdominal muscles.
  4. Contract your glutes and extend your legs into the air by lifting your hips off the floor. Make sure to keep your abs contracted. Think about lifting through your heels and press your feet up towards the ceiling. The bottom of your feet should be facing the ceiling at about shoulder-width.
  5. Point your toes in towards your shins. Pause as you keep your abdominal muscles tight, and reverse the movement until your hips are touching the floor. This is now the starting position.
  6. With your legs extending up, repeat the movement. 
  7. Perform up to 3 sets of 10 to 12 repetitions.

Safety Precautions

There are a few more important things to know about knee ups: 

  • Always be aware of your back position and make sure that it is straight and never arched in any way.
    • As is the case for most exercises, you will need to think about  scapular retraction, which is a squeezing of the shoulder blades that is good for your posture. However, when you are doing knee ups, you actually need to protract your shoulder blades. 
    • Since the knee up requires you to lie flat on your back, pregnant women that are no longer in their first trimester should avoid doing this exercise. If you are pregnant,  exercise can be beneficial as long as it is cleared by your doctor.  
    • It can also be hard for obese people to complete the movement required by this exercise, so performing alternatives or progressions is encouraged. Also, i
    • If you have been experiencing any neck, knee, or lower back pain, it might be better for you to try a different exercise, reduce the number of reps you are doing, or ask your personal trainer to help you with the movement.
    • If you feel any pain during this exercise, stop what you are doing, and review all of the steps we explained above. 

    Because of the position of your body, watching yourself do a knee up is not especially easy. To make sure your form is correct, consider asking your personal trainer (or your gym buddy) for some help.

    Alternative Exercises 

    Like many other exercises, the knee up is also known by a variety of different names. Some of the moves that are similar to the knee up and work the same muscles include the reverse crunch on a bench and the leg pull-in. 

    If you are not quite ready for the knee up, or if you are looking for other moves to strengthen your core and especially your lower abs, here are some other exercises that will also specifically target your abdominal muscles and give you a great abs workout:

    • Reverse crunches
    • Sit-ups
    • Bicycle crunches
    • Planks
    • Hanging knee raises
    • Hanging leg raises
    • Flutter kicks

    Get Crunching 

    If you follow a well-designed strength training program and if you try to eat as well as you can, you might find yourself easily gaining impressive amounts of muscle and strength. But usually, after 6 to 12 months of doing knee ups, your progress may slow down considerably. You will need to create a long-term plan to keep getting stronger. A good way to add extra bulk and power is with the  Mass Stack.

    Do a bit of research into which type of diet might be best for your specific needs. There are so many different types of wellness diets that you will need to select one that matches your goals of either  bulking your body up a lot more or shedding excess body fat and slimming down as much as you can.

    As with all types of exercise, knee ups can offer you all kinds of benefits and rewards. By simply including knee ups and other bodyweight exercises in your core workout routine, you will quickly begin to realize several specific benefits. 

    Strengthening and maintaining a healthy core is key to improving athletic performance, performing daily activities, and preventing injuries. 

    You can do knee ups individually, add them to a resistance training session, or include them in your regular workout.

    If you really want to see continual progress and keep strengthening your abs, always include proper warm-ups, rest, and a good nutrition program. Always remember that weightlifting and cardio  can both burn calories.

    Your results will be based on all of these factors combined, and on how well you can recover from your workouts. To allow your body enough time to recover, we suggest resting for 24 to 48 hours before training the same muscle groups.