Work Your Core With Lying Leg Extensions

Core strengthening exercise programs almost always include some type of lying leg extensions. Depending on the position you’re in, lying leg extension exercises might work your abdominal, pelvic, back, hip and/or knee muscles.

Before deciding whether and how you’ll include lying leg extensions in your back exercise program, it’s a good idea to get the terminology straight.

Technically, leg refers to the lower leg, but many people use this term to refer to the entire lower extremity. When you lie on your back and lift your lower extremity with a straight knee, you’ll be flexing your hip and extending your knee. You could also keep your knee bent; this is usually recommended for beginners who have little abdominal muscle strength and/or those dealing with low back pain.

When you lie on your stomach, you’ll be extending your hip as you bring your lower extremity up towards the ceiling. In this case, you could either keep your knee extended, i.e., straight, or you could bend it, which is called knee flexion. The choice is yours, but each variation will likely make a difference as to which muscles are worked.

Prone (on your stomach) lying leg extensions are a bit more advanced, and best added into an established program.

Woman doing leg lift on a mat
SrdjanPav / Getty Images 

Good Alignment Will Help You Target Your Core

Regardless of the terminology, prepare for lying leg extensions by positioning yourself with good alignment and engaging your core muscles. As the leg lifts, pelvic and trunk movement will likely result. Your job, or rather the job of your abdominal muscles, is to not let that movement happen; this is how core muscle strength is built.

Core stabilization work such as this targets the transverse, internal and external oblique abdominals the most. But the rectus abdominis muscle, which you may recognize as the “washboard abs” also participates in the movement.

Most people with back pain can get a lot out of a very simple supine (on your back) lower extremity lift. In fact, one or more variations of supine lifts are usually very quickly given to spine patients by their physical therapists.

How to Do a Beginner’s Lying Leg Extension — Supine

  1. Lie on your back on a hard surface, preferably the floor. This is so your muscles don’t have to work too hard to keep you in good alignment; the floor can support you instead. If you’re on a wood floor, also consider doing the exercise barefoot so that your feet don’t slip.
  2. Bend your knees and put your feet flat on the floor.
  3. Inhale, and keeping the angle of your bent knee the same throughout the movement, lift your lower extremity. Note that the lifting movement happens at your hip joint.
  4. As you lift the lower extremity, try not to allow your trunk position to wobble, waver, shift or change in any way. Hint: It’s all in the abs.
  5. Exhale and place your foot back on the floor. Again, be mindful that you trunk stays stationary. Also, remember to preserve the lower leg to thigh angle.

Many people, whether they realize it or not, use gravity to help get the foot back down to the floor. But working this way tends to have the effect of “skipping” the abs, which won’t do you much good if a strong core is what you’re after. To interrupt this counterproductive exercise habit, consider slowing down the pace at which you bring your lower extremity back to the start position. It’s fine to slow down during the lift phase, too.

How to Do a Beginner’s Lying Leg Extension — Prone

  1. Lie on your stomach with your elbows bent, your palms on the floor even with your shoulders, and your lower extremities extended. Keeping your forearms resting on the floor, drag the points of your elbows into the same direction as your feet, in other words, away from your shoulders. This may result in a stretch of the muscles at the tops of your shoulders, as well as a supportive position for your mid and upper back.
  2. To engage your core and establish good low back alignment, pick your belly button up from the floor just a little.
  3. Inhale and fill your core with air. As you exhale, lift one lower extremity up off the floor. This does not have to be a big movement. Remember, the goal is to strengthen your core which requires that you keep the pelvis in the same position it was when you established your start position. Trying to get height to the lower extremity movement will most likely result in extraneous trunk movement; this won’t work your core.
  4. Inhale and place the lower extremity back down to the start position.

Whether you practice this exercise on your back or on your stomach, about 3–10 done with excellent form are all you need. Taking care to maintain a stable trunk position and good alignment as you extend your leg is key to working the muscles that can help your back.

1 Source
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Oliva-Lozano JM, Muyor JM. Core muscle activity during physical fitness exercises: a systematic review. Int J Environ Res Public Health. 2020;17(12):4306. doi:10.3390/ijerph17124306

By Anne Asher, CPT
Anne Asher, ACE-certified personal trainer, health coach, and orthopedic exercise specialist, is a back and neck pain expert.