Exercise Analysis - Hip Flexors
Regular readers can probably recite my hip-flexor-versus-ab rant better than I can write it. But the fact of this matter is simple. Gym goers continue to perform leg raises that involve no change in spinal alignment to target their abdominals even though the rectus abdominis (the major abdominal muscle) only crosses and acts at the joints formed by adjacent spinal vertebrae. But this month, instead of dwelling on the negative, I’m going to focus on a situation where the performance of leg raises is desirable. That would be when one’s intention is to train the hip flexor muscle group.
Hip flexion is a dirty word when it comes to abdominal training, but it’s actually quite an important motion in general. Every time we take a step forward, we flex our thigh at the hip. If those steps are rapid (i.e., we are running), these contractions must be performed with considerable power. So, whenever locomotion is the goal, a very capable set of hip flexors is desirable. Any activity that involves kicking is also highly dependent on these players.
There are many muscles that contribute to hip flexion. Three of the major ones (psoas major, psoas minor and iliacus) comprise the iliopsoas group. A fourth (rectus femoris) also crosses and acts at the knee, so its ability to work in concert with the others depends on knee joint angle. Other minor hip flexors contribute minimally and only under specific postural circumstances.
As is apparent from my oft-repeated abdominal advice, leg raises are an effective exercise for targeting the hip flexors. However, just like every other muscle we train with weights, opposition to movement must be sufficient so that the ability to perform repeated contractions is limited and it’s also important to ensure that the fatigue that causes termination of a set is located in the region being targeted. So, in simple terms, if you are performing any kind of leg raise for your hip flexors, a load must be applied that causes the muscles in front of your hip to cry “Uncle!” in two minutes or less.
Leg raises can be done with the body either perpendicular to or in line with the pull of gravity. In other words, you can do them lying supine or standing. In addition, you can hang from a bar with your arms extended overhead (hands gripping the bar) or positioned down at your sides (elbows atop a padded horizontal support). Many gyms also have slings that allow you to hang from an overhead bar with a reduced requirement to grip. This is beneficial because if your grip goes south before your hip flexors, you won’t be able to continue performing leg raises until the requisite degree of effort in the muscles you are targeting is attained.
There are a number of ways to provide opposition to hip flexion. An ankle weight is a viable option, as is an ankle cuff with a ring that you can attach to a cable coming from a low pulley. The range of resistance offered by cable machines is typically greater than that offered by ankle weights, so the latter option is desirable over the long term. However, if relatively heavy weight is required or if a history of knee problems (particularly ligament damage) is present, thought should be given to applying the load above the knee instead because doing so will eliminate the shear force at the knee that ankle application entails.
The lower back is another area that is vulnerable when performing weighted hip flexion. Every time your hip flexor contracts to raise your thigh, its point of origination on the hip serves as an anchor against which the shortening muscle will pull. Flawed integrity of this base of support will result in the hips rotating forward. And wherever the hips go, the spine will follow! Consequently, exacerbation of the neutral lumbar curve (excessive lordosis) that places considerable stress on intervertebral discs will occur on each repetition you perform. To prevent this, it is essential to stabilize your hips by engaging your abdominal muscles isometrically throughout your set. Chronically shortened hip flexors (typical in people who spend a lot of time sitting) can also wreak havoc on lower back health by pulling the hips forward when you stand. Exercises designed to augment hip flexor strength also have the potential to shorten these muscles, so a hip flexor strengthening program should include lunge stretches to end-range hip extension that help to maintain optimal muscle length.
Weighted hip flexion is often used during knee rehabilitation when motion at the injured joint is restricted (when afflicted with patellofemoral syndrome, for example). There are four muscles that extend the leg at the knee (the quadriceps) and three of them cross the knee exclusively, so they are not prime movers during hip flexion. However, they are responsible for keeping the leg straight (stabilizing the knee by virtue of an isometric muscle action) as weighted hip flexion is performed, so they receive some stimulation. And, as previously mentioned, the fourth muscle of the quad (rectus femoris) is a prime mover during hip flexion, so this knee muscle can be targeted in this way without excessively stressing the joint.
This article was originally published in New Living Magazine, which can be accessed on-line at www.newliving.com.
