One way of grounding is to deliberately press your foundation into the floor.
Someone, a fellow teacher, once said that you can't press into the ground. Gravity is already pulling us down!
That is true, to an extent, and almost makes sense, unless you consider the idea that generally we don't pay much attention to our foundation.
When we press a particular part of our foundation (or all of it for that matter) into the ground with the intent of pushing strongly, there is a noticeable change in the sensation at the foot. And if you pay attention, you may also notice a change in sensation in the muscles related to whatever part of the body you are pressing into the earth.
If you are into feeling and controlling your anatomy while doing yoga (or other activities) one concept that might be useful is that of muscle trains. These are based on (or inspired by) Thomas Myers work with the Anatomy trains concept.
Before talking about these trains of muscle, an important idea to bear in mind is that any muscle needs a stable foundation for controllability.
Whether you are trying to deliberately relax a muscle or active it, it helps if one bone to which that muscle is attached is stable.
As an example of how stability affects us, it's relatively easy to relax the body lying on a hard surface such as the ground. In this case the stability is provided by the ground.
Standing upright, it is relatively easier to relax when standing on ground that is non-slippery.
Trying to stand upright on ice it can be a lot more challenging to relax as much as possible while standing upright.
Upping the stakes a little, to remain upright on ice while standing with legs spread apart.
On a non-slippery surface, friction can be used to help you maintain your leg position. As a result you can relax your leg muscles or activate them. You have control because the non-slippery surface provides stability.
On ice it's a different matter.
You have to use muscular effort to keep your feet from sliding apart. As a result it's impossible to relax your legs while maintaining that leg position.
Because the surface is slipper and non-stable, you lose control. Or the control effort is being expended to keep you in place.
A general way of talking about stability is that it is the resistance to change.
Standing with legs reasonably wide on a frictional surface, friction provides the resistance to change, the stability. On ice, muscle power provides that resistance to change.
Say you wanted to deliberately spread your legs on a frictional surface. Then you could use muscle power against friction to spread your legs apart.
Now, instead of resisting change you are using your muscles to create change.
So one way of looking at muscles is that they can create change or they can resist it.
In order to control muscles and create a desired change it helps if muscles have a stable foundation from which to act.
On a frictional and stable surface we have the choice of trying to spread the legs or pull them inwards. In either case we use muscle power to create the change we desire.
On ice, we loose the option to choose.
We loose the ability to control our legs because we are on a slipper or non-stable surface.
Muscles connect from one bone to another.
To control a particular muscle (or set of muscles) it can help if one bone to which they are attach is stable. This gives them a stable reference point to create a change.
As an example, the serratus anterior attach between the ribcage and the shoulder blades.
If the ribcage is stable then the serratus anterior can be used to protract your shoulder blades relative to your ribcage.
If the shoulder blades are stable then the serratus can be used to move the ribcage relative to the shoulder blades.
Your shoulder blades will still protract, however, instead of the shoulder blades moving relative to the ribcage, the ribcage moves relative to your shoulder blades.
In either case what is important is that one of the sets of bones to which the serratus attaches is stable.
That provides a reference for movement, a stable foundation from which a desired change can be created.
A stable foundation gives a muscle a foundation from which to act, a foundation or reference point from which to create change.
From Thomas Myers anatomy trains, one of the most important idea to be gained is that muscles connect to each other across joints via continuous sheaths, or trains, of connective tissue.
You could visualize muscles like a series of sausage links, each sausage representing a single muscle and the connection between each sausage representing a muscle's connection across a joint to the next muscle along. Or as Thomas Myers did, you can visualize muscles like passenger or freight trains. So an anatomy train would be a series of muscles hooked up like the carriages of a train.
Passenger or freight trains are pulled by a locomotive. One major difference is that muscle trains don't need a locomotive. They provide their own motive power.
What they do need however, is a stable anchor point.
Since each muscle requires a stable end point from which to act, the idea then is to create a grounding point for the entire train.
This point of stability acts as an anchor for the first muscle which in turn acts as an anchor for the next muscle (carriage) in the train.
How then do you create the initial anchor point, an initial point of stability?
I'll go over two main possibilities for creating anchor points.
One is based on the idea of relative mass, the other on "grounding" and the use of body weight.
Fire a gun and the bullet travels a lot faster in a forwards direction than the gun moves in a rearwards direction. The bullet has a lot less mass than the weapon that fired it and so because of the differences in mass the bullet travels a lot faster than the gun even though both are being driven by the same expanding ball of gases.
In the same way, because we are so much smaller than the earth, the earth doesn't move when we push against it. Instead, doing a push up, we move relative to it.
Applying this to our body, if one part of the body to which a muscle attaches has more mass than the other part, then the part with less mass can be pulled by the muscle towards the part with more mass. The more massive bone (or bones) acts as an anchor or foundation for the less massive body part.
Using the straight leg sit up as an example, if you allow your knees to bend as you try to sit up, your hip flexors, working between the weight of your body and the weight of your thighs, pulls the knees up, and your body remains on the ground.
Keep the knees straight then the relatively higher mass (and/or moment arm) of the legs is enough so that the hip flexors then cause the torso to lift instead of the legs.
If you are not used to doing straight leg sit ups, and are worried about the possible shearing force exerted by the psoas major on the lumber vertebrae, one option is to do this slowly. Do it slowly so that you can stop if you encounter pain or other problems. While trying this exercise, focus on sitting up without lifting your legs and notice what your knees do. Also notice the sequence of events that your head and chest and arms follow as you try to sit up. You may notice your head lifts first, then your torso (your arms are probably reaching forwards), then you start to tilt your body upright. You could think of this as changing various moments and moment arms to keep your legs on the floor as you sit up.)
So one way of creating a foundation from which muscles can act is to stabilize a joint locking the two bones that meet there together.
Generally, you can stabilize a joint by using opposing muscles against each other. But you can also stabilize a joint by using a set of muscles against body weight.
So again using the straight leg sit up example, you can use the quadriceps against the weight of the shins to stabilize the knee joint. The hamstrings and/or calfs don't have to activate to oppose the quads because the force of the quads is being resisted by the weight of the lower leg.
The legs as a whole then can act as an anchor for the hip flexors and abs so that the torso can be "sat up" relative to the legs.
So the general idea here for creating stability is to unify the masses of the part of the body that you want to use as a foundation. That can mean stabilizing the joints so that the bones that are joined by that joint move as one.
The cool thing about this is that not only does this lock bones together, but the act of using muscles against each other adds tension to those muscles which can then be used to anchor whatever muscle trains those muscles are a part of.
Another way of creating an initial anchor point is to use body weight.
As an example, standing on one foot, you could shift your weight to anchor the outside edge of the foot. Anchored in place by the weight of your body above it, the outer edge of the foot then serves as an anchor point for the calf muscles, and any other foot muscles that attach there.
One set of muscles that attach or wrap around the outer edge of the foot are the peroneus longus and brevis (fibularis muscles).
Both of these muscles attach to the fibula, the smaller of the two lower leg bones.
The biceps femoris long head and short, part of the hamstrings group, both attach to the fibula. With the outer edge of the foot anchored the peroneus muscles can create a downward pull on the fibula. The fibula then acts as a potential anchor point for the biceps femoris. The short head can then act on the femur while the long head can, from the fibula, create a downwards pull on the sitting bone or ischial tuberosity.
Pressing down through the heel, (and here it may be helpful to "stack" the heel) the heel then acts as a potential anchor point for the two calf muscles, the soleus and the gastrocnemius.
The soleus attaches to the tibia and fibula. It may be useful in a similar way to the fibularis muscles, creating a downward pull on the fibula, particularly if the heel is weighted but the edge of the foot is not.
The gastrocnemius passes between the two sets of hamstrings tendons to attach to the femur. Activating this muscle from an anchored heel, it can then push outwards on the hamstrings tendons, adding tension to them which then helps to give these muscles a fixed end point from which to create a downwards pull on the ischial tuberosity.
Standing on one foot, it is possible for the shin to rotate relative to the foot.
Muscles that cross the ankle joint can be used to stabilize the shin against rotation. This same action can be used to maintain the arch of the foot.
With the shin stabilized also, and more specifically, the tibia, the tibia can act as an anchor for the hip muscles that attach to it.
As an example, the iliotibial tract attaches to the top of the tibia, just in front of the fibula. This band of connective tissue passes up the side of the thigh to attach to the crest of the pelvis.
The tensor fascia muscle attaches from it to the front point of the crest of the pelvis (the ASIC or anterior superior iliac crest or "point" of the hip) while fibers of the gluteus maximus attach from it to the rear of the iliac crest (the PSIC or posterior superior iliac crest).
With the tibia stable both of these muscles have a stable foundation from which to act on the crest of the pelvis.
I'd suggest here that the gluteus maximus attachment may be more important in front bends while the tensor fascae latae attachment may be more important in back bends for the hip. But that's a guideline, not a hard rule.
The important idea here is that body weight can be used to provide the initial anchor point, whether the heel, the outer edge of the foot or both.
Hanging by a bar from your hands, say with the intent of doing leg lifts, the fingers could act as the main anchor point.
Muscles that attach from the fingers to the forearm or upper arm bones could act from the fingers (which are in turn being acted on by the weight of the body) to stabilize the arm bones.
One connection that may be potentially important is that of the biceps, one of the heads of which attach from the connective sheath of the forearm to the coracoid process.
Acting from the forearm to anchor the coracoid process, this then gives the pectoralis minor, which also attaches there, an anchor point from which to act on the ribcage.
This may then give the abs, particularly rectus abdominus, a stable foundation from which to act on the front of the pelvis. It may also give the obliques a firm foundation from which to act on the ASIC which in turn gives the hip flexors there (the rectus femoris, and possible tensor fascia latae and sartorius) a firm foundation from which to pull upwards on the legs.
Note that these aren't the only "trains" that are active. But they provide one possible path that you can use to trace through the body.
Part of exploring a pose or action could be exploring all possible lines of muscle action that can lead to the succesful execution of a pose or action, or a minimal perceived effort pose.
An important compliment to the idea of stabilized muscle trains, is the idea of joint capsules and ligaments as active structures and as the possible key element in terms of why the brain activates pain signals.
Another related concept is that of overlapping morphic tensegrity units. The point of overlap is the joints, and the reason for overlap is to allow for smooth transitions between shape changes while maintaining joint integrity.
Active joint capsules and overlapped morphic tensegrity units may also provide a tool for exploring (and fixing) knee, hip and low back pain.
Anchoring the base of a muscle chain sometimes isn't enough to help a muscle contract effectively. Another option for creating muscle controllability is by adjusting muscle slackness.
In the picture, my daughter is in the process of balancing on a slack line. One of the only things that I taught her was to focus on pressing the foot down onto the slack line.
So rather than lifting the body up, I taught her to focus on pressing down.
This is general technique for creating stability, particularly in the hip joint, but because the focus is on the foot (which is pressing down), this simple action stabilizes the foot and makes the entire leg an anchor for muscle trains extending up from the foot and leg to the rest of the body.