Workout first, explanation second.
Step 1: Release
Take a lacrosse ball, tennis ball, golf ball, softball, baseball, cricket ball, or spiky ball, it doesn't matter, it just needs to be something that resembles an elbow that will get dug into the little muscles in and around the hips.
Take your ball of choice and stick it right under the middle of your butt cheek, you are hunting for the piriformis muscle. Shift around over the ball looking for tight spots. Once you find a particularly tight spot relax down, camp out on it and let the pressure do its magic. You can learn more about trigger points here.
From the middle of the glutes, you are going work up into the back corner of your pelvis and glutes, along the ridge of iliac crest hunting for trigger points across the top of glute max and the posterior fibres of your glute med.
From the back corner of the hip, take the ball to the front corner of the hip around the front pocket area, just below the hip bone, working through your TFL. Learn more about the TFL here.
If you're feeling adventurous take the ball and roll further around from the TFL, lying flat on your belly and release the psoas.
Psoas runs inside the abdomen and attaches to the front of the femur, with the hips flat to the ground you can put a little pressure on the bottom third of the muscle and give I some release. Try and relax sinking into the ball. This one's not for everyone, it makes you feel a bit like you want to spew.
Step 2: Stretch
Once the torture is finished with the ball, it's time to do the world's most important and greatest stretch, the kneeling hip flexor. Make sure you have something soft for your knee, and it helps to have a wall, table, or chair close by to balance with.
Up tall, draw in your belly button, posteriorly rotate the pelvis to tuck your butt under, and squeeze the glute of your back leg. Hold that position for 30-seconds each side.
The most common mistake we see with this stretch is people push their hips right forwards in order to feel the stretch. What ends up happening is the lower back arches and your pelvis tilts forward into an anterior pelvic tilt. In this position it becomes really tricky to keep the core and glute engaged, the spine is jammed up and the psoas is not fully stretched as it simply rotates around pulling the spine forwards.
The pelvic tilt solves all these problems. If you keep your butt tucked down under, the glutes squeezed and belly button drawn in to hit that stretch properly. Holding on to a chair, long roller or wall helps provide an extra bit of balance to steady you into the stretch, allowing the muscle spindles to fully relax.
Step 3: Activate
The third and final part of the mini-workout is a bit of glute activation. 10 squeeze and lifts, followed by 10 bridges.
So now for the explanation:
When we sit, our glutes and hamstrings are compressed against the chair under our body weight. Over time, this causes blood flow restriction and compresses the nerves deactivating the muscles. That compression on the glutes is particularly uncomfortable for the sciatic nerve.
Because the sciatic nerve runs right under (or in around 22% of the population through) the piriformis as the piriformis tightens it compresses and restricts the sciatic nerve, potentially leading to piriformis syndrome. It's not uncommon for piriformis syndrome to be confused clinically* with sciatica (This paper goes in depth on the topic).
Releasing through piriformis and waking up weak glutes can do wonders for releasing this pressure on the sciatic nerve which has the knock on effect of improving your hamstring and calf flexibility as well.**
* Always see a professional for any pain or injury.
** More often than not your hamstring or calf tightness is linked to a tight sciatic nerve.
The hip flexor stretch is all about one key muscle, the psoas.
Psoas is an interesting muscle, it connects to the front of your lumbar spine, runs over the top of your pelvis through the abdomen, and then connects to the front of your femur.
Sitting for hours on end gradually shortens and tightens the psoas gradually causing an anterior tilt of the pelvis where the pelvis begins to slope forwards. This anterior pelvic position jams up the lower back, tightens hamstrings, inhibits glutes and weakens the core. On top of all that it can create the impression of a little postural pot-belly.
The worst thing about this anterior pelvic tilt is it's a vicious cycle of tightness, weakness, and pain. The psoas gets tight from sitting, This builds an anterior pelvic tilt, which in turn creates weakness in the glutes and core, which can lead to lower back pain. As a result of the sore lower back, the psoas locks up further in a splinting mechanism further driving the glute weakness and anterior pelvic tilt.