I think we can universally agree that lifting heavy things is awesome. Unlike other primary movements, deadlifts require minimal degrees of freedom in order to be successful. Your ankles don't flex, your knees stay above 90, your back stays relatively straight; however, your hips begin the movement in near full flexion.
Being a hip dominant exercise there should naturally be a significant amount of strain at the hip musculature. Your hips are comprised of your pelvis and femur, therefore whatever connects them are your prime movers. What connects your pelvis to your back and femurs to your tibias would be considered stabilizers (still working, but not as hard). If you complete a round of deadlifts and only feel one group of muscles that connects the hips, or that group of muscles is not even considered a prime mover, something is not right.
People will often jump up in arms and say that deadlifts are a back exercise. That by moving from a flexed forward position to upright that your back has to be a prime mover. That is incorrect. When you begin a movement in a back extended position (such as the deadlift), it is not the job of the back extensors to move weight. It is the job of the back extensors to maintain extension while the weight tries to produce back flexion. Back extension should not be your primary strategy for making yourself upright. Extending a flexed joint, such as the hips during a deadlift, is the prime motion. Therefore hip extensors are prime movers.
Your hamstrings and glutes are the prime movers for the deadlift. In the initial pull, where your hips are maximally flexed and your knees are bent between 85-45 degrees, your hamstrings stabilize your knee while your quads extend your knees and your glutes begin to extend your hips. This phase is often characteristic of a strong contraction and some serious leg shaking. As you get closer to clearing your knees and your knees become straighter, your hamstrings begin to take on a greater hip extension role. Finally the last few degrees of hip extension are driven by your glutes and you achieve an upright stance.
There are several scenarios where technique may play a factor in how we leverage muscles but a simple youtube search will be able to help you there. For those who feel their technique is pretty solid but they either cannot keep their back from dominating the movement or they never feel their backside legs working, we will dive deeper into the hips.
Here we have hip internal rotation as measured in the seated position. Typically we want 45 degrees of this motion for several reasons. In regards to deadlift performance we want more than 40 degrees of IR at the hip because as the pelvis flexes over the top of the femur, the femur moves backward into the socket. This same motion occurs with hip IR. Essentially, if you sit on a high surface and cannot do that with your leg, you either cannot control your femur in the socket (active < passive motion) or your socket doesn't allow for the motion to occur (passive =active and is less than 40*).
In the former you will often see someone flex forward and easily touch their toes, but when they do so you see an exaggerated lumbar curve. This is due to the compensatory nature our back will adapt to protect us against an "unstable" or weak hip. In the ladder you will often see the opposite. As one flexes forward their sacrum continues to slant upward toward the sky and the low and upper back adopt and exaggerated rounded curve. This is due to the lack of pure hip flexion with extra spine flexion to make up for it.
The pairing of these two tests (hip IR and forward flexion) can tell us a lot about what is limiting motion but nothing replaces seeing the patient/client perform the activity in question. The first intervention might not be more deadlifts with minor corrections, but it might be. And if it is, you best be getting what is necessary from the person your paying, not whatever they can reason in their heads.
First, establish full hip extension on both legs, then each leg individually. If the issue is predominant on one side you do not want all of your interventions to be symmetrical bilateral stance or you will compensate right through and nothing will change.
Second, ensure you have appropriate abdominal capacity to pull the ribs down and back (if your ribs are flared then your pelvis will anteriorly tilt and your posterior capsule musculature will tighten, closing the posterior capsule down). AKA, no hip flex here!
Third, clear out restrictions from the calves and low back, as these will also hold the pelvis in a position that limits IR and forward flexion.
Fourth, train internal rotation. This means adductors and anterior gluteus medius muscles. These are often ignored and rarely touched on in a typical training program. Maybe that's why your hurt!
Fifth, deadlift correctly.
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