How to Do a Vertical Knee Raise

Proper Form, Variations, and Common Mistakes

Also Known As: Captain's chair

Targets: Hip flexors, abdominals

Equipment Needed: Parallel bars or dip/raise machine

Level: Intermediate

The vertical knee raise is a core exercise that lets you add variety to your ab workout while also taking it to a more advanced level. If you're after the elusive six-pack abs, adding the vertical knee raise can help you along your way. You can use it as part of a core workout or total body workout.

Knee raises are best performed on a dip/raise machine, but you can also do them suspended between two parallel bars. The machine, which is found in most health clubs and sold for home use, includes a back pad that will help support you and keep you from swaying during the exercise. It will also likely have pads on each of the parallel bars where your elbows and forearms can rest in a comfortable and stable position.


The core muscles the vertical knee raise works are the ones that you show off: the rectus abdominus. This muscle is responsible for spinal flexion and lets you do things like sit up from a lying position and other motions involving pulling your chest down toward your hips. It runs through your torso, extending from your sternum down to your hips.

The vertical knee raise also targets your hip flexors. While your rectus abdominus is stabilizing your core during the exercise, your hip flexors are doing the work of bringing up your knees.

The vertical knee raise came in second on the list of best exercises for the rectus abdominus. A 2001 study at San Diego State University compared 13 common abdominal exercises to determine which ones really strengthen the abs.

The exercises were ranked for muscle stimulation—measured with EMG—in the rectus abdominus, as well as the internal and external obliques. The captain's chair exercise was one of the few ab exercises on the "most effective" list that requires gym equipment.

Step-by-Step Instructions

Position yourself on the dip/raise machine, back against the pad and arms holding your body up by resting on the parallel bars. There should be hand grips to hold onto at the ends of the parallel bars, and there are usually foot bars to step up on to get into position.

  1. Take your feet off the support, allowing your legs to dangle. Inhale.
  2. Slowly bend your knees and lift them toward your chest while exhaling. The motion should be controlled and deliberate as you bring your knees up until your thighs are parallel to the floor.
  3. Continue to bring your knees up as high as you can without rounding the upper back off of the backrest and looking down. You will work the abs more once your knees are higher than parallel to the floor.
  4. Slowly return your legs to the starting position, while inhaling.

Common Mistakes

To get the most out of the exercise, avoid these errors.

Letting Legs Drop

Don't simply drop your legs or you will lose half of the benefit of the exercise. Slowly return them to the starting position.

Using Momentum

Don't do this exercise fast or swing your legs up or down as that will use momentum rather than muscle to perform the exercise.

Extending Legs

When new to this exercise, keep your knees bent. Performing it with the legs extended rather than bent knees will emphasize the hip flexors more than the abdominals and place more stress on the lower back. As your hips get stronger, you can keep your knees extend your knees for a deeper workout.

Modifications and Variations

You can do this exercise in different ways to match your level of fitness.

For Beginners

If you are new to the exercise, it is best to use a dip/raise machine rather than parallel bars as it will help you maintain the correct position and reduce swaying. You may only be able to raise your knees partially at first. Aim to do the exercise slowly and with control no matter what your range of motion. As you build strength you will be able to get your thighs parallel to the floor and eventually more toward your chest.

More Intensity

If you are ready for a challenge, you can vary the vertical knee raise while increasing the intensity by holding a weight between the knees. Start with very light weights for this to get accustomed to the higher load and to holding and controlling the weight between your feet.

You can also increase the intensity by lifting the legs laterally without bending the knees. However, this adds significant strain to your back, so exercise caution if you try this to avoid injury. 

Safety and Precautions

You may need to avoid the vertical knee raise if you are pregnant or recovering from childbirth, have rectus diastasis, had recent surgery on your abdomen, or are recovering from injuries or surgery involving your back, neck, arms, or legs. In some cases, you may be able to perform the move with modifications.

Ask a trainer at your gym or a physical therapist for recommendations. If you feel any pain while performing this exercise, return to a safe position and end the exercise.

Try It Out

Incorporate this move and similar ones into one of these popular workouts:

1 Source
Verywell Fit 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. American Council on Exercise. New Study Puts the Crunch on Ineffective Ab Exercises. 2001.

By Elizabeth Quinn, MS
Elizabeth Quinn is an exercise physiologist, sports medicine writer, and fitness consultant for corporate wellness and rehabilitation clinics.