What is hip extension?
In terms of your body, everything you do involves a rotational force, or torque, around a pivot. By this we mean a muscle contracts creating force, that force is exerted at a lever creating a turning moment. In the case of hip extension and flexion you have a lever formed by the skeletal structure of the hip girdle and spine that move into flexion or extension as the glutes, hamstrings and spinal erectors or hip flexors respectively contract. Hip extension is one of the most basic human movement patterns; think of bending over to pick something up. In its simplest form hip extension takes us from bent over at the hips to standing up right. Good mornings, back extensions and kettlebell swings are the purest hip extension movements we can do in the gym, although deadlifts, cleans, snatches and squats still involve a high degree of hip extension. It is one of the strongest, most powerful movement patterns available to the human body. Think about pushing you car when it won’t start, you don’t stand straight up and push, you bend from your hips, activating your hamstrings and glutes and push like that, your body knows this is much more powerful.
Why is hip extension important?
Respected strength coaches such as Dan John have been touting the benefits of hip extension movements for years for everything from increasing your total, a more developed posterior chain, full body power development, better movement quality and even a better quality of life! Indeed Gray Cook has included hip extension movements in his famous functional movement assessments and believes them to be one of the most important basic movement patterns. There is a large body of research evidence demonstrating hip extension as a vital part of most athletic activities from sprinting to jumping. Hip extension has even been shown to play a vital role, even sports traditionally thought of as rotational in nature, such as baseball hitting velocity, rotational throws like shot put or hammer or the golf swing.
EMG studies in both baseball and golf report highest muscle activity of the primary movers of the posterior chain; the hamstrings, glutes and low back, happens during the beginning of the forward swing. The exercises listed above are often programmed because they target the same muscles. Very conveniently, those muscles are also responsible for creating rotation in the swing. Here’s the key point: good hip rotation has an element of hip extension!
This is what it looks like from the front and side in a baseball swing:
Check out the belt line as the hitter transitions from landing with his stride foot to making contact. This is the actual unloading of the hips during the forward swing. You should be able to see how the hips (belt line) lower into flexion (load) and then actually come up a bit as the hips extend (unload). Unfortunately, the baseball EMG study only measured muscle activity on the back leg. The golf EMG study, however, measured both legs. An interesting point from this golf study is that in the initial forward swing (from the loaded position to horizontal lag position), activity in the quadriceps of the lead leg was higher than the posterior side (glutes, hamstrings, biceps femoris, semimembranosus). This makes sense because the front side is accepting some shifting weight during this time. But, when the club is being moved from the horizontal lag position to contact, the hip extenders again become more active. Indeed baseball and golf instruction both commonly refer to having a “firm front side” or “posting the lead leg” this EMG suggests extension at the hip, rather than the knee, is more responsible for creating this effect.
Interestingly a recent study into lateral jump performance, a frontal plane movement considered an important indicator of performance in rotational sports (which makes sense as the ability to decelerate the front side after the lateral weight shift has occurred must also be vital in creating this firm front side), found the only direct correlation in improving lateral jump was hip extension performance. In other words of all the strength movements tested only improving strength in the hip extension movement pattern resulted in a longer lateral jump.
How should you train hip extension?
When training hip extension, specificity of movement should be considered. As can be seen above rotational sports, such as golf, baseball or tennis, require a blend of hip rotation and hip extension to produce maximum power. Training should reflect this; powerful movements that share this blending of rotation and extension include medicine ball throws as rotational cable movements such as shown below
Another thing to consider is where your sport lies on the speed-strength continuum; swinging a baseball bat or golf club or throwing a shot or hammer are relatively low strength, high speed explosive movements. Your training should therefore be towards the speed end of the continuum, again think medicine ball throws, power versions of the clean or snatch, or speed deadlifts against accommodating resistance.
Additionally, a recent review of literature in strength & conditioning research (amazing resource that you should check out by the way!) also demonstrated that hip torque is often lower at lower strength training ratios. Simply put this means, when completing a movement in training or practice the hip extension force exerted is often lower than that used on the field, court or course on game day. In order to manage this potential deficiency it may be wise to add some additional pure hip extension movements, in the form of hip rep good mornings, back extensions or kettlebell swings into your training.