The bridge exercise is a simple and effective exercise to begin working on hip extension and turning on your glutes. This in itself is so important to restoring muscle imbalances of the lower extremity and core. Common postural adaptations include excessive anterior tilting, which in turns makes it difficult to extend the hip and really activate your glutes, specifically your gluteus maximus.
However, another common finding with anterior pelvic tilting is tight hip flexors. Early phases of rehabilitation and corrective exercise should attempt to improve hip flexor mobility, however this tightness also limits your ability to extend the hip and thus activate and train the gluteus maximus.
So what do we do? Traditionalists will say that we need to restore mobility before working on strengthening. I agree with this, but also think there are ways to work round your limitations to make progress with both hip flexor mobility and hip extensor activity simultaneously.
There is a simple modification that we can do to the bridge exercise to maximize hip extension. Rather than perform the exercise with our legs parallel in the sagittal plane, try putting your feet closer together and slightly separating your hips. This puts your hips in slightly more external rotation and abduction, as seen in the below video. Note that improvement in my ability to extend my hips:
Why this Improves Hip Extension and the Bridge ExerciseThe reason why this modification allows us to extend the hips more is due to the action and orientation of the iliopsoas muscle group.
In addition to flexing the hip, the iliopsoas group also externally rotates the hip. This is not discussed nearly as much as hip flexion, but something to consider.
Furthermore, if you look at the picture, you can see that the orientation of the iliopsoas group is not straight in the sagittal plane, but rather, slightly abducted (something to keep in mind when stretching as well).
To shorten the iliopsoas group as much as possible you need to position the hip in slight external rotation and slight abduction.
In order to maximize our ability to contract the gluteus maximus and extend the hip, we need to put our body in a position that shortens the hip flexors as much as possible.
Try this simple modification for the bridge exercise and let me know if you can achieve more hip extension.