Balance Hip Flexors and Ab Muscles With Pilates

If you take Pilates classes or fitness classes, you might hear the phrase, "Stay out of your hip flexors." The hip flexors are a group of muscles toward the front of the hip. Their main role is to help bring the thigh and trunk of the body closer together, say, for instance, when you move your leg and knee up toward your body.

Technically, the hip flexors include the iliacus, psoas major, pectineus, rectus femoris, and sartorius muscles. Of the group, the iliacus and the psoas, which attach your pelvis to your femur (thighbone) and lumbar (lower) spine, are probably the most important. Collectively, though, all these muscles play an important role. You use them in many daily activities, including walking, stepping up, and bending over.

How Hip Flexors Take Over Ab Workouts

Obviously, you need your hip flexors. But you usually don't need them as much as you use them in ab exercises. When you target the abs, you perform exercises that decrease the distance between your thigh and trunk—think sit-ups, roll-ups, and leg lifts. The hip flexors are a strong group of muscles, and they try to take over—so you end up working your hip flexors more than your abdominal muscles.

A perfect example is the kind of sit-up where you put your feet under something that holds them down and then do a bunch of sit-ups with an almost flat back. Those mostly work your hip flexors. People who do Pilates run the same risk with the many flexion (forward-bending) exercises they do.

Signs of Strong Hip Flexors and Weak Abs

Low back pain and soreness in the groin area may be signs that you're weak in the abs and overusing your hip flexors. Another clue is not being able to keep your feet and legs down when you do a sit-up or roll up. What happens is that the abs aren't strong enough to do their up-and-over contraction, so in order for the trunk and thigh to get closer together, the hip flexors take over, and the feet fly up.

The reverse of hip flexion is a hip extension, which occurs when you increase the angle between your thigh and the front of your pelvis. A good example is when you move your leg to the back. Your gluteus maximus (aka your butt muscles) and your hamstrings are primary muscles of hip extension. It's important for the muscles of hip flexion and hip extension work together in a balanced way, and many people have weak or tight hip extensors. 

How to Get Out of Your Hip Flexors

This isn't always simple. A lot of people have to constantly work at not engaging their hip flexors. For one thing, you can't really leave the hip flexors entirely out of most ab exercises—they're still an important part of the picture. The idea is to get in the habit of involving the abs as much as you can to keep the hip flexors from taking over.

Your first line of defense is always awareness. When you do Pilates or other ab-focused work, put your attention on your abdominal muscles. These basic Pilates exercises can increase awareness and set the foundation for abdominal strength and body mechanics that balance ab and hip flexor use.

• Knee fold: In this exercise, the abdominal muscles stabilize the pelvis, so you can feel the subtleties of the hip flexors at work. Try to keep big muscles, like the quadriceps of the thigh, out of the exercise as much as possible.
• Chest lift: This exercise engages all the abs, but it feels more like an upper ab exercise. Stabilize the pelvis in a neutral position and move just the upper body in isolation. Your hips and legs should stay still and not grip. If the hip flexors start to get over-involved, you might have a sense that your knees want to pull toward your chest or tightness in the groin and thigh.
• Supported roll back: This exercise invites a deep abdominal scoop. As you roll back, you might sense a point where the hip flexors want to grab the movement. You can feel that at the crease of your thigh. As you roll down, try to focus on rolling down and controlling the abs. Think about getting some space between the top of the thigh and the lower abs.
• The Hundred modified: The full hundred calls for the legs to be extended, something the hip flexors often see as a call to over-action. Performing the hundred in a modified position with your knees bent and feet flat on the floor, or legs in tabletop, can help you focus on using your abdominals.

A Word From Verywell

As you work on increasing your awareness of the relationship between the abs and the hip flexors, you'll discover there's reciprocity in terms of one set of muscles doing the stabilizing of the trunk or pelvis while the other set moves. What you want to achieve is a muscular balance, better functionality, and ultimately more choices about how you move.