Lying Knee Up: Classic Body Weight Exercise To Work Your Lower Abs

If you’ve ever tried to do a lying knee up and struggled to keep your form in check, you’re not alone. Many people experience difficulty when attempting this popular exercise, and the reasons why can vary. It’s important to understand that your struggles with the lying knee up likely stem from underlying muscle imbalances or weaknesses. The good news is, with a little bit of guidance, you can remedy these issues and improve your form in no time. In this post, we’ll explore the common causes of faulty lying knee up form and provide helpful tips for correcting it.

Lying Knee Up Summary

  • Primary Muscles: Iliopsoas (Psoas Major & Iliacus)
  • Secondary Muscles: Adductor Brevis, Adductor Longus, Pectineus, Rectus Femoris, Sartorius, and Tensor Fasciae Latte
  • Equipment: Body Weight
  • Mechanics Type: Isolated
  • Force: Pull
  • Utility: Auxiliary
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Lying Knee Up Instructions

  • Setup by laying on your back on a mat or the floor.
  • Place your hands down to each side to support your pelvis. Raise your legs by flexing your core and thighs.
  • Pull your knees up to vertical.
  • Then, return your legs to point and body straight.
  • Repeat the Lying Knee Up for a full set.

Video Tutorial

Lying knee tuck exercise

Lying Knee Up Muscles

Target (Agonist)


  • Adductor Brevis
  • Adductor Longus
  • Pectineus
  • Rectus Femoris
  • Sartorius
  • Tensor Fasciae Latae

Dynamic Stabilizers

  • None


Antagonist Stabilizers

  • None
Image of the skeletal muscular system with the muscles used in the lying knee up exercise highlighted in red and the rest in blue.

Benefits of Lying Knee Up

The lying knee up exercise is a great way to target the iliopsoas muscles, which are often neglected in strength training or fitness routines. This exercise can help to develop and strengthen these important muscles, which are responsible for hip flexion and external rotation of the thigh. Strengthening the iliopsoas muscles can help to improve posture and reduce lower back pain. Additionally, this exercise can help to increase hip mobility, improve balance and stability, and enhance overall athletic performance.

Tips for Performing Lying Knee Up

You’ve come to the right place if you’re motivated to advance your lying knee up performance. Using these tips can enable you to maximize the advantages of this beautiful exercise. You will shape your core muscles, and even reduce your chances of experiencing an injury. It is time to begin and take a look at how these suggestions will help you.

  • Engage your core: Make sure to keep your core tight throughout the exercise to keep your spine in a neutral position and maximize the benefits of the movement. This will help prevent any lower back pain or injury.
  • Keep your neck in line: Align your head with your spine and keep your eyes facing forward to ensure that your neck is in a comfortable and safe position throughout the exercise.
  • Control the movement: Take your time to slowly and smoothly move through each repetition. Control the motion of each knee up to ensure you are not using momentum and really engaging the muscles you are targeting.

Benefits and Tips Video

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Frequent Mistakes To Avoid

When executing lying knee up, avoiding typical errors can be the difference between an effective workout and a debilitating injury. From bad form to not engaging your core, these mistakes can reduce the productiveness of the exercise and can even raise your risk for injury. But relax, it’s not as challenging as it might seem. By knowing the mistakes to avoid and taking the appropriate actions, you can execute the exercise securely and successfully. Let’s begin by staying away from these typical errors and add this exercise to your exercise regimen.

  • Not engaging their core muscles – Not engaging their core muscles during the Lying Knee Up exercise means that they are not activating the right muscles, which can lead to an ineffective workout and not achieving the desired results.
  • Moving too fast – Moving too quickly during the Lying Knee Up exercise can cause improper form and may even lead to injury. It’s important to take your time and focus on each movement in order to get the most out of the workout.
  • Not stretching beforehand – Not stretching before doing the Lying Knee Up exercise can cause tightness in your muscles and joints, leading to a less effective workout and potential soreness afterward. Taking a few minutes to stretch before your workout can help you get the most out of it.

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Variations and Complementary Exercises

The Lying Knee Up is a great exercise to work your lower abs, but it can be difficult to do without proper form. To make sure you’re getting the most out of this exercise, here are a few variations, complementary, or alternative exercises that work similar muscles:

Leg Lift

Graphic image of Leg Lift.

Leg Lift is a great complementary or alternative exercise to the Lying Knee Up. It is a full body exercise that works the lower body, core and upper body. To perform a Leg Lift, begin by lying flat on your back with your legs together and your arms at your side. Lift both legs up in the air at a 90-degree angle and hold them there for a few seconds before lowering them back down. This exercise is great for developing core strength, balance, and coordination while also helping to strengthen the hips, glutes, and hamstrings. Additionally, it can help improve posture and range of motion while providing an intense workout.

L Sit Hold

Graphic image of L Sit Hold.

The L Sit Hold is a great alternative or complementary exercise to the Lying Knee Up. It works the core and lower body in a way that can improve balance and posture, and it can also help to increase strength and stability in the abs, hips, glutes, and lower back. By placing your hands on the ground, feet together and knees bent, you will lift your legs up off the ground while keeping your torso upright and straight. This isometric hold will challenge your core and hip muscles as they work to keep your body stable and upright, while providing an excellent static workout. It is a great exercise for developing core strength and stability, as well as improving posture.

Hollow Bench Hold

Graphic image of Hollow Bench Hold.

The Hollow Bench Hold is an excellent alternative or complementary exercise for the Lying Knee Up. This exercise primarily works the core and can be done with or without weights. It involves lying on the floor with arms extended above the head and legs raised off the ground. The participant then holds the position for 30 to 60 seconds, feeling the tension in their abs and lower back. The Hollow Bench Hold also works the glutes, hamstrings, and hip flexors for a full-body workout. It is an excellent way to challenge the core muscles and build stability and strength.

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Cross Body Mountain Climbers

Graphic image of Cross Body Mountain Climbers.

Cross body mountain climbers are an excellent complementary or alternative exercise to the lying knee up. Cross body mountain climbers involve starting in a plank position and bringing one knee up towards the opposite elbow before returning to the plank position. This exercise helps to engage the core and leg muscles, while also providing a cardiovascular challenge. It is a great way to mix up your routine while still working on the same muscles as the lying knee up.

Scissor Kicks

Graphic image of Scissor Kicks.

Scissor Kicks are a great complementary or alternative exercise to the Lying Knee Up. It is an abdominal exercise that works the rectus abdominis, the internal and external obliques, and the hip flexors. To perform this exercise, you lie on your back and raise both legs up off the ground so they form a “V” shape. You then move your legs in a scissor-like motion, alternating between bringing your right leg down and then your left. This exercise can be performed with or without resistance, making it suitable for all fitness levels. It is an effective way to strengthen and tone your core muscles, while also providing a cardiovascular challenge.

Hip Lift

Graphic image of Hip Lift.

Hip Lift is a great complementary or alternative exercise to Lying Knee Up. This exercise targets the glutes, hamstrings and core muscles by engaging them in a controlled movement. It is performed by lying on your back with your feet on the floor, and then lifting your hips up off the floor as high as you can. This exercise helps to strengthen and stabilize the hip, thigh, and core muscles, as well as improve overall balance and flexibility. Additionally, it can help to prevent injury by strengthening the core and glutes. The Hip Lift also works in conjunction with the Lying Knee Up exercise, as it helps to strengthen the muscles in the lower body, while also providing a good stretch to the hip flexors.

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Opposing Complementary Exercises

In order to maximize the benefits of the exercise Lying Knee Up and to prevent injury, it is important to incorporate complementary exercises that work the opposing muscle groups. This will help to maintain balance in the body and to ensure that all muscles are being worked equally. Below are a few exercises that can be used to do just that.

Bird Dog Plank

Graphic image of Bird Dog Plank.

Bird Dog Plank is a complementary exercise to Lying Knee Up as it targets the opposing muscle group. Bird Dog Plank involves starting in a plank position on your hands and toes and then extending one arm and the opposite leg out so that they are parallel to the floor. This exercise works the core, shoulders, and hips while also engaging the glutes and hamstrings, which are the opposing muscle groups of the quads and hip flexors used in Lying Knee Up. By including both of these exercises in your workout routine, you can get a full body workout that targets both the major and minor muscle groups.

45 Degree Twisting Hyperextension

Graphic image of 45 Degree Twisting Hyperextension.

The 45 Degree Twisting Hyperextension is a great complementary exercise to the Lying Knee Up. This exercise works the lower back and glutes, which are the opposing muscle group to the abdominals and hip flexors used in the Lying Knee Up. It is performed by standing on a hyperextension bench, bending forward at the waist, and then twisting at the waist while keeping the legs stationary. This exercise targets the lower back, glutes, and obliques while also strengthening the core. The 45 Degree Twisting Hyperextension is an excellent way to round out a core strengthening routine and balance out the effects of the Lying Knee Up.

Cable Glute Kickbacks

Graphic image of Cable Glute Kickbacks.

Cable Glute Kickbacks are a great way to complement the exercise Lying Knee Up by working the opposing muscle group. This exercise is done by attaching a cable to a low pulley and then attaching an ankle cuff to the cable. Then you stand with one foot on the cuff and the other foot on the floor. You then extend your leg back and then return to the start position. By performing this exercise, you are working the gluteus maximus, which is the opposite muscle group to the rectus abdominis that is worked in Lying Knee Up. This is an effective way to build strength in both of these muscle groups and achieve better overall balance in the body.

Stronger Core, Healthier You: Master Your Lying Knee Up Today!

One key component of overall fitness is a strong and stable core. A stable core can improve balance, posture, and even help prevent injury. One exercise to add to your core routine is the lying knee up. When performed correctly, this exercise targets the lower abs as well as the hip flexors. A strong lower core can also improve athletic performance in sports such as running, jumping, and cycling. So, by mastering the lying knee up, you can improve your overall fitness and achieve a healthier you!

References: Wikipedia | | | Comprehensive List of Legs Bodyweight Exercises

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