While doing some research about marichyasana, I found out from another author that doing Marichyasana A with the Marichyasana hip lifted is a way of exercising the SI Joint.
Doing it with the hip down, the same effect is not achieved.
Or so he suggested.
I've had the opportunity to explore the muscles of the legs and hips in detail recently, and in the context of seated yoga poses like Marichyasana A and I'd suggest that what is more important than lifting a hip or keeping it on the floor in marichyasana is actually being able to activate the SI Joint so that you can stabilize it in either position (or anywhere inbetween).
Another option is to stabilize the hip bone and or femur so that muscles that work on the SI joint have a stable foundation from which to act. (Stabilizing the foot and lower leg can also be helpful in this regard).
Before we go on, SI is short for sacro iliac.
The SI joints are where the two innominate bones or hip bones connect to the sacrum.
Each Si joint is partially fibrous and partially synovial where synovial means that there is a fluid between adjoining surfaces.
In men the SI Joints tend to be fairly immobile while in women they can be very mobile, which is very important during child birth. This mobility allows the pelvis to flex in one direction so that the upper opening of the pelvis gets larger and then flex in the opposite direction so that the lower opening of the pelvis gets larger. This allows the babies head to pass through.
However, even without the rigours of child birth to deal with, the SI Joint is important because it allows the pelvis to handle the stresses imparted to it by forces transmitted between the legs and spine. And this is important for both men and women.
The connective tissue that holds the si joint together is what transmits these forces while keeping the pelvis intact.
And so that forces can effectively be transmitted, the SI Joints allow the Hip Bones and sacrum to move some amount relative to each other.
And so it helps to think of the pelvis, which is made up of the hip bones and sacrum and includes the SI Joints, as a flexible structure.
Marichyasana A is one example of a an asymetric seated forward bend. Each of the legs is in different positions. And this can have a different effect on the two SI joints.
In Marichyasana A:
So not only is each hip bone going to be affected differently by the position of the legs, the sacrum is going to be asymmetrically affected by the lean of the spine . As a result both SI joints both experience different forces.
And this will be the case whether the bent knee hip is lifted or on the floor. And it will also be the case whether the foot is close to the inner thigh of the other leg or separated from it a hands breadth or so.
Stress isn't a bad thing. Exercise is a form of stress, so in terms of strengthening or exercising the SI joint, stress is a good thing.
And another point is that the more ways you deliberately stress the SI joint while exercising, the stronger and more durable it will become.
An important point is how you stress it. Passively stressing any joint may be the equivalent of bending a piece of metal repeatedly. It's going to eventually weaken.
However, if you make the joint active in some way, then you are strengthening the joint.
This doesn't mean that you should consciously try to use muscle all of the time to keep the joint strong. Rather you are training muscle so that those muscles can be used when required to keep the joint strong.
Additionally, for any joint, you can strengthen it in two ways. One is to work on the muscles that work on the joint. Another is to focus on the joint itself.
The knee joint might make it easier to explain this idea.
With the knee joint, you could work on strengthening it by training:
The quadriceps, hamstrings and gastrocnemius muscles.
In addition you could also work on strengthening the long hip muscles. The long hip muscles all work on both the hip and knee joint. These muscles include those muscles that work on the IT Band (Superficial Gluteus Maximus and Tensor Fascia Latae) as well as the gracilis, sartorius and semitendinosus (which is also one of the hamstrings muscles.)
You could work at learning to activate these muscles and use these muscles in various combinations against each other. With the quadriceps and hamstrings in particular, it's relatively easy to activate these muscles consciously and use them in such a way that the knee feels stable. Likewise with the gastrocnemius, one of the calf muscles.
However, another method is to simply make the knee feel strong.
Whether the focus is on the knee joint, or muscles that act on it, the knee will be affected, but the effect is slightly different in each case. And rather than saying one method is better than the other, I tend to train my students in both activations.
And actually, the focus is more on control as opposed to strength.
Another important consideration when dealing with knee strengthening is creating a stable foundation. One way to create a stable foundation for the knee is to stabilize the foot and lower leg bones. Another way is to stabilize the hip bone and femur.
In either case, this stable foundation provides an anchor point for muscles that work on the knee.
With the SI joint, a similiar approach can be used.
I've already talked about stabilizing the SI joints using the transverse abdominus, pelvic floor muscles and sacral and lumbar multifidus in other articles. These muscles can work together in different configurations to stabilize both SI joints at the same time.
To provide an anchor point for leg muscles that work on the SI joint, a simple method is to focus on stabilizing the femur and or hip bone since there are muscles that cross the SI joints that attach to both of these bones.
The long hip muscles can also be useful since they attach to the corner points of the hip bones. Since the other ends of these muscles attach to the lower leg bones, one way to give these muscles a stable foundation is to first stabilize the lower leg bones. To do that, you can stabilize the foot and ankle.
A simple method for doing this while in marichyasana is to press foot of the bent knee leg down strongly into the floor.
Since I've already talked about stabilizing the knee, yo should note that "stabilizing the knee" is another way to anchor these muscles.
An important point when pressing the foot down is to prevent the same side hip bone from moving upwards while you press down.
To do that, you have to unify your body in such a way that it resists the hip moving upwards as you press the foot downwards. This is irregardless of whether the hip is already lifted or positioned on the floor.
If you've ever tried to push a car out of a snow bank or out of mud, you know that when you push forwards with your hands you don't let your hips move back. Otherwise you lose the power that you've generated. Now imagine that the car is really hard to push out, so you have to use maximum force. But despite that, the car still doesn't move. But, neither does your body.
That is the effect you are trying to achieve when you push your foot down. Your body resists being pushed upwards and as a result you can press down with close to all of your body weight.
When pushing your marichyasana foot into the floor it's as if you are using your foot to push the floor away from yourself. However, you don't let your body move. You consciously keep your hip from lifting so that you can powerfully push your foot into the floor.
Note, this is a lot easier if you aren't binding.
If you aren't binding you can use your arm on the straight leg side to help brace your body.
If you are binding, the try pushing your straight leg down against the floor to help brace yourself.
As you press your foot down, you'll notice an increase in pressure in your foot, and you should notice muscle activation in your thigh and hip region. And if you are bracing yourself with your hand, your hand should also press down more strongly too. It has to in order to prevent your hip body from moving.
This should stabilize your hip bone.
One advantage of not binding in this position is that you can use your arm to brace your body. As a result, your spinal muscles will be active. How active they are depends on how much you are pressing with your bent knee foot and the opposite hand. In other asymmetrical seated forward bends like hurdlers stretch or janu sirsasana, you could have your hands lifted, and as a result your spine will be bearing a lot more body weight.
Whether you are using your hand (or hands) to help or not, one thing that you can do with the hip stable is to adjust yoru spine relative to that hip.
A very simple adjustment is to raise or lower the bent knee hip so that your SI joints feel comfortable. Another way to adjust is to adjust the position of your spine. You can do that by adjusting the forwards or backward tilt of your pelvis.
You can also further adjust your spine, particularly in the lumbar region, by adjusting the position of your ribcage relative to your pelvis.
How do you know when an adjustment is correct? By the way it makes you feel. It's something that takes practice and experience. This can be speeded up with exercises and instructions designed to help you improve sensitivity and muscle control.