While reading Andry Vleeming’s latest book Movement, Stability, and Lumbopelvic Pain: Integration of Research and Therapy, I was introduced to the relatively novel idea of the deep sacral gluteus maximus and the role it plays in the overall function of the pelvic girdle by Sean Gibbons. Admittedly, there are a few things that make me say “hmmm…” maybe this just another set up like the VMO fibers and an academic discussion, but nonetheless, it is interesting.
Muscles that Matter: Deep Sacral Gluteus Maximus
The gluteus maximus has received a great deal of attention in performance and rehabilitation circles for a broad range of conditions and with good reason. The gluteus maximus has the ability to support and contribute to force transfer about the pelvis via its insertion into the thoracolumbar fascia.
The gluteus maximus has been subdivided into many segments and as of late, has been divided into three specific segments: superficial sacral, deep sacral, and deep ilium fibers.
The deep sacral fibers are important in the stabilization and force closure of the SI joint and can be divided into superior and inferior fibers.
The superior deep sacral gluteus maximus are most superior of all subdivisions and cross the sacroiliac joint to attach at the posterior pelvic brim. The inferior fibers are oriented inferior and laterally as the run from the lateral sacrum to the posterior ischium, ischial tuberosity, and the sacrotuberous ligament.
As the idea of “deep sacral gluteus maximus” is novel, few studies are available that examine its neural function. In one study, it was shown that there was no separate innervation at the DSG than from other subdivisions, which makes me wonder if we are treating this like the VMO and upper/lower rectus abdominis.
However, electromyographical analysis has shown that the deep sacral gluteus maximus is active during vertical loading and in positions of sacral counternutation like proper hip hinging. During trunk twisting activities the DSG also becomes active independent of other subdivisions of the gluteus maximus. Based on what we understand of sacral motion in gait, the DSG may play a role in controlling sacral torsion and providing dynamic stability about the pelvic girdle, making it a valuable asset to performance.
Other factors to consider
Much like the psoas and other inner unit musculature, there seem to be motor control deficits in patients with low back pain with activation of the deep sacral gluteus maximus proving to be more challenging in these people. Athletes with low back pain also demonstrated significantly higher activity in global mobilizers including the hamstrings and the rectus femoris. I wonder, again, here if we are just looking at the run-o-the-mill gluteal amnesia aspects, which are commonly associated with increased hamstring and erector spinae tone as in Janda’s Lower Crossed Syndrome.
Training the Deep Sacral Gluteus Maximus
Training the DSG in isolation may be an exercise in futility, however, many of the things we are already doing in training may benefit the DSG provided motor control is adequate. The addition of a loaded rotational component that is hip driven like the “rotational row” can be a good tool to stimulate the DSG’s activity while sparing the spine simultaneously provided an athlete has the range of motion available.