Here’s a discussion on gluteal and pelvic biomechanics. In this video, I discuss several important concepts, including:
- How the glutes protect the low back,
- The transfer of forces from the glutes to the rest of the body (how a glute squeeze creates hip extension torque, hip external rotation torque, and posterior pelvic tilt torque at lockout, creating a highly stable position),
- Why you should keep the glutes turned on during kettlebell swings while the bell is floating, and
- How posterior pelvic tilt mimics hip hyperextension.
In case you missed Skelly, he’s back!
The thing I don’t understand is how glute squeeze & posterior pelvic tilt protects the spine from, for example, shearing forces (mechanically this doesn’t make sense to me, though it definitely works, I can feel it). I have a theory (but no science to back it up) – could the issue be that the glute squeeze is inhibiting the hip flexors? That would reduce the strain on the spine caused by the erectors firing to counter the torque of the hip flexors pulling the hip into anterior tilt, which would create lots of shear force. If the glutes fire to counter the hip flexors then the load on the spinal erectors drops, which could explain the relief from pain and reduction in shear force (just an idea).
Also, on an unrelated note, several traditional martial arts emphasize a stance (called sanchin in karate) where the pelvis is slight tucked – the reason they recommend that are usually vague, but I imagine at some point somebody intuitively understood the benefits of that position on the spine. Just an fyi.
I specialize in the functioning of the voice and mainly work with singers. There is a long tradition in Old School Classical singing of figuratively “pinching a dime” to elicit a gluteal squeeze.
The reason for this is when the glutes contract there is sympathetic contraction of the deep abdominal muscles, which contribute to the stabilizing of the spine. This is important in high intensity singing which relies on strong breath compression, which is a product of the deep abdominal muscles.
Without a stable spine this would not be possible, so the glute contraction helps to make both results more complete. Also I suspect that the glute contraction stabilizes the pelvis which then contributes to the stable spine.
Thanks Michael! I did not know that. Explains much.
Great insights, Michael!
One way to think of this is to look at the lockout position of a DL in a static hold. Weight is in front of the spine.
Much like a seesaw, or better, a winch, the glutes roll the pelvis down which supports the spine from the back to match the force of the load from the front pulling the spine forwards and down. A counterbalance.
(The same “tug of war over a hill” takes place in a postural sense between the pec minor and the lower traps at the shoulder, with the pec minor usually winning.)
I agree Derrick and this was proposed in an older journal article I have in my possession. However, some other research attempts to refute this. I was hoping my visit to Stu’s lab in Waterloo would shed some light on this topic as I’d like to get to the bottom of it. When I lock out a deadlift, I feel the glutes pulling upward on the torso via posterior tilt. So I’m with you here!
Phillippe has a nice answer below, regarding the thoracolumbar fascia. (Grasovetsky!)
Consider that the lats are also pulling extremely hard on TLF from above. We know the lats provide a powerful anterior tilting force on the pelvis.
Perhaps this is another tug of war, the lats and glutes both firing very hard from opposite directions, opposing forces acting on the TLF, to create protective “girdle”, further buttressed by ab force on the other side.
Interesting discussion.
Thanks for the info Michael! Fascinating!
The Gluts, when contracted, pull tension and create torque through the lumbodorsal fascia, which stabilizes the spine. (simple answer)
Philippe, fyi – this tensioning appears to be quite exaggerated according to a recent recent modelling (4 Nm ain’t much): http://www.ncbi.nlm.nih.gov/pubmed/23959791
Hi Joe, I love the way you’re thinking!!! I would say that when PPTing, you inhibut the APT mechanism, so the hip flexor and erector activation would diminish a bit. I’ll test this out in the glute lab shortly.
I confess to not quite knowing the exact mechanism either; perhaps squeezing the glutes prevents the lumbar spine from maximally hyperextending, thus sparing the posterior elements.
I agree that it could reduce shear force, but I could also make the opposite case and argue that the erectors counter the shear force induced by the load pulling down on the torso. Biomechanics ain’t easy haha!
At any rate, you’re a great thinker, so I applaud you.
Bret I hope you get to this question of mine – how do you balance activating glutes and preventing this shear at the bottom of the deadlift (bracing and breathing correctly, and activating glutes from the get go) and maintaining a back arch? I find thinking about activating the glutes puts me in PPT at the bottom of a DL, which has made me miss or pull with a rounded back. I guess I’m overdoing the glute cue or something? Is there a point in the lift where you cue the glutes and not from the very beginning?
Great question John! Agree – don’t think of the glute squeeze at the bottom as this could pull you into PPT and thus lumbar flexion. Think of holding the arch (which is mostly erector). I cue the glutes after the bar passes the knees.
Thanks for the incredible comments and questions folks! I’m very lucky to have some very bright readers 🙂
Derrick,
Another great comment!
Regarding Gracovetsky, here’s Stu McGill’s research showing that the lumbodorsal facia doesn’t create much of an extensor moment when activated by the abs or lats: http://www.ncbi.nlm.nih.gov/pubmed/3236850
Gracovetsky replied to this, but I lean with Stu on this one.
And regarding the latissumus dorsi, here’s an article showing only 6.3 Nm of extensor moment generation (which isn’t much): http://www.ncbi.nlm.nih.gov/pubmed/11415812
This is why I always attribute most of the lumbopelvic stabilization in a squat or stoop lift to the erector spine – there’s no arguing that they do the bulk of the job! Sure everything else can contribute, and I’m fascinated by what the glutes/abs can do via PPT, but we need more research to be confident about our hypotheses.
Again, great dialogue!
Hi Bret,
SInce I’ve read your article about learning a new way to perfom back extension,
I felt much better during this exersice. It’s hard for me to come up from the bottom position with rounded back (like you did in that video), but I used your cue about doing posterior pelvic tilt . It’s deffinitely more comfortable for my lower back than the other version.Thank you for the great cue!
I am also trying to squeeze the glutes hard at the top of the hip thrust and dealift, but for some reason I feel the contraction only in my right glute. I assume that it’s glute imbalnce. I am perfoming activation drills for the weaker side every day and still I almost don’t feel anything during th exersices. Could you please recommend me what should I do, if my left glute simply refuses to “fire”? I feel my stronger side even during the activation drill for the weaker side.
POlina
Polina, I wrote two good articles (and filmed a video) on glute imbalances. Find them in the search bar of my blog (or just search Google) by typing in “bret contreras glute imbalances” – you’ll love these! Best of luck, Bret
I’m a naturally thin 5″3, 108 pound 21 year old female with major back issues. I only recently discovered that it is due to being hyper mobile and now I am cautious of how I stretch and train.
I was reading comments and I agree I don’t really feel “that burn” when I squat or do bridges, I only feel my lower back and top thighs working! the only way I feel my butt triggered is one legged squats but even then I can tell my hips are not aligned properly when I do them so I’m worried of causing more damage!
I really wanna get a nice toned butt but my hips and hyper flexibility are holding me back 🙁 any advice?
Hi bret,
I suffer from piriformis syndrome, and during most leg extension workouts my piriformis cramps so bad that I should stop. Which glute excersice is piriformis friendy? I myself found squats to be be better than glute bridge and leg press for example.
Bret – I am having some internal existential dilemma over the topic of PPT in the DL lockout
1. I believe Stuart McGill when he warns against allowing PPT at the bottom of the squat. This creates a mechanism for disk injuries. So, I limit my ROM to what I can do before I experience PPT. I do not want to allow heavily loaded flexion-extension cycles.
2. PPT in the DL lockout does not seem fundamentally different from that in the squat, from the L5-S1 POV. The disk is still in compression, and there is motion at L5-S1, and probably further up the chain. PPT and lumbar flexion tend to happen together.
So – while I agree that PPT at DL lockout is the correct way to do a DL, how would you rationalize allowing one, but not the other from the POV of disk forces and potential for injury?