Let's begin with a mechanistic view of this pose. In a initial movement of a deadlift position, the knees are bent, the hips are hinged, and the trunk is forward, coming infront of your Center of Gravity and outside of your base of support. It is mostly taught, to have the lumbar spine 'flexed' or in a posterior pelvic tilt. Mechanistically, we know that in physics when this occurs, the amount of 'torque' load at Lumbar vertebrae 3 mostly and 4, is going to increase tremendously- even before additional weight is applied. In a restorative or injury prevention training, I would teach lumbar spine neutral and work on increasing both psoas and hamstring length to help maintain lumbar spine neutral (that is just the beginning). Keeping the hamstrings long enough to allow as close to 'neutral spine' in the lumbar spine as possible at the beginning of this pose because moving into a flexed lumbar spine with your trunk outside of your center of gravity will increase the load more on the anterior portion of the vertebral body. This means, there is 'unequal' force as compared to an 'equal' compression load in 'neutral spine.".
Remember, that this position, in and of itself is going to increase the compression loads on the spine by shear movement of the trunk away from the center of gravity.
Then, we add tight hamstrings, which do not allow, the pelvis to remain in 'neutral' alignment, instead pulling the pelvis into a flexed lumbar spine and posterior pelvic tilt.
We need to hold up for a second. It is important to note that this discussion is about 'prevention of injury' and 'restoration of a balanced muscular system in spite of being in the 'deadlift' posture. Some coaches teach that lumbar flexion in the deadlift is the way to go. I am not saying that is wrong. What I am saying, is this: Just know what you are doing from the mechanistic aka arthrokinematic point of view, in order to determine which position of your spine is good for you at that time. Yes, you can get initially get more POWER from a Flexed lumbar spine for several reasons: 1) it turns on the pelvic floor and transverse abdominus by shortening some of these muscles. 2) It shortens the hamstring at the proximal end , so therefore when you go from the transition of knees bent to knees straight, you can potentially achieve a bit more power as well. HOWEVER, this is where Restorative Personal Training can guide the athlete into maintaining positions of power while preventing injury. It does however, take a bit more time to train this way, because initially , you will lose power in your deadlift. The reason being, because you have changed the mechanics of the posture and now you must re-train the hamstrings, transverse ab, pelvic floor muscles, psoas , lattisimus dorsi, and the erectors of your spine to recognize this new place in space as related to your limbs, head and center of gravity- it's called kinesthetic awareness.
The training to 'sense in' to having the ability to isolate each small instrinsic muscle and inquire whether or not it is turned on or off or needs more attunement- takes a bit of time and skilled intervention.
Deadlifts, involve many, many muscles that interact with one another and at any given point, if there is a weakness in one of those areas, can create a change big enough to strain, sprain, or herniate in the back. Gross motor muscles that are interconnected fascially in this posture include but are not limited too: latissimus dorsi, erectors, psoas/iliacus, all 3 hamstring insertions, and your iliotibial band/tensor fascia latae.
From a restorative/mechanistic point of view, deadlifts can create potential injury and signs could look like this but not limited too:
- pain in the front of the shoulder, pain in between the shoulder blades, pain in the lower back, pain in the inner knee, pain in the front inner knee, pain below the knee cap, pain in the buttocks region near the sitting bones, pain near the coccyx region, pain in the ribcage posterior and anterior, pain in the space between the ribs and the hip on the side. Interesting to note as well , that many of individuals that perform Strength and Conditioning Power Bodybuilding have very high pain tolerances and pain may not be their way of telling them something is not right. This is why it is important to have help , assessing alignment and movement within the joint spaces, within the capsule, and having sensory integration techniques performed with a skilled and trained individual to help bring to the participants awareness of physiological, muscular, nervous system, and skeletal events that may lead to potential injury or may be preventing more strength gains from occurring. It is pretty safe to say, that if one has received an objective diagnoses from a qualified physician that there is indeed a herniation in the lumbar spine- that one should take caution when performing a deadlift in a flexed spine as this will only exacerbate the herniation over time. Signs do not have to include back pain with a flared up herniation. They can also include hip 'sticking', alignment issues, clicking in the hip or back, changes in gait, changes in strength, changes in the proximal or distal joints, trigger points in the innervated musculature, facial tightness, and referred pain sites such as inbetween the shoulder blades or near the posterior lower rib cage and much much more.
I regularly see a crossfiter who has a history of a diagnosed herniation- you know who you are and I love you! Through the years, we have watched how easy it is to mistake knee and hip pain for 'pure muscular' issues, when infact it is stemming from the consistent chronic repetative compressive loads put on the herniated disc through deadlifting. Please remember, your form may be Perfect but even in the most optimal form, due to the mechanistic/arthrokinematic alignment that this posture demands, there will be no way of avoiding a certain amount of increased compression and increased potential of torque. Considering all that is happening here such as the latissimus dorsi engaged along with the psoas and hamstring while the trunk is away from it's Center of Gravity.
Without getting to much more into describing the kinesiology of these muscle groups, think about the force that is placed at the L3,L4 vertabrae when all these things are applied: trunk outside center of gravity, pull from hamstrings on pelvis, pull of psoas muscle on L1-L5, pull of lats through the thoracolumbar attachment site. And that is just a few of the forces all culminating at this already structurally degraded site.