The SR Stance mobilizes and coordinates some of the most powerful muscles in the body to maintain key joint angles and keep a skier in balance and over their skis against the constantly changing 3-dimensional external forces associated with skiing that tend to disturb skier equilibrium.
The SR Stance is best learned outside the ski boot in an environment where the feet and legs are free from any influences. One of the benefits of learning an SR Stance outside the ski boot is that, once learned, it provides a reference against which to assess whether a ski boot supports the functional parameters of the skier. If it doesn’t, the SR Stance can be used as a reference to guide equipment modification and establish when and if it meets the functional requirements of the skier.
The SR Stance tensions the pelvis from below and above; below from the balls of the feet through the PA-soleus-gastrocnemius-hamstring muscles to the pelvis and above from the shoulders-latissimus dorsi-trapezius muscles to the pelvis.
The graphic below shows the Achilles Tendon junction with the PA at the heel bone.
The graphic below shows the 3 major muscles of the leg associated with the SR stance.
The Soleus (left image in the above graphic) extends from the back of the heel bone (see previous graphic) to a point just below the knee. It acts in concentric contraction (shortening) to extend or plantarflex the ankle. In EC-SR, the Soleus is under tension in stretch.
The Soleus is one two muscles that make up the Triceps Surae.
The Gastrocnemius (center image in the above graphic) extends from the back of the heel bone to a point just above the knee. It acts in concentric contraction (shortening) to flex the knee. In EC-SR, it is under tension in stretch where it is acting to oppose extension of the knee.
The Hamstrings (right image in the black rectangle in the above graphic) extends from a point just below the knee to the pelvic girdle. It acts in concentric contraction (shortening) to flex the knee. In EC-SR, it is under tension in stretch where it is acting to oppose extension of the knee.
A number of smaller muscles associated with the SR that will be discussed in future posts.
The graphic below depicts the 3 steps to learning an SR Stance.
- The first step is to set up a static preload on the shank (shin) of the leg.
The static preload occurs when the tension in the soleus muscle of the leg simultaneously peaks with the tension in the sheet-like ligament called the plantar aponeurosis (PA). The PA supports the vault of the arch of the foot. The soleus is an extension of the PA. This was discussed in my post ZEPPA-DELTA ANGLE AND THE STRETCH REFLEX.
- While barefoot, stand erect on a hard, flat, level surface as shown in the left hand figure in the graphics above and below. The weight should be felt more under the heels than under the forefoot.
- Relax the major muscles in the back of the legs (mainly the hamstrings) and allow the knees to move forward as shown in the right hand figure in the graphics above (1.) and below.
- As the knees move forward, the hips will drop towards the floor, the ankle joint will dorsiflex and the angle the shank forms with the floor and the angle of the knee, will both increase until a point is reached where the shank stops moving forward on its own. Movement of the shank will probably be arrested at a point where a plumb line extending downward from the knee cap ends up slightly ahead of the foot. This is the static preload shank angle.
2. From the static preload shank angle, while keeping the spine straight, bend forward slightly at the waist. The angles of the shank (ankles) and knees will decrease as the pelvis moves up back and the weight will shift to the balls of the feet. Bending at the waist tilts the pelvis forward. As the pelvis tilts forward, it stretches the Hamstrings and Gastrocnemius causing the knee and ankle to extend. Tension in the Hamstrings and Gastrocnemius extends the lever arm acting to compress the arches of the feet from the top of the shank to the pelvis thus increasing the pressure on the balls of the feet through Achilles-PA load transfer.
3. From the position in 2., round the back and shoulders as you bend forward from the waist.
Make sure the core is activated and tightened as the back and shoulders are rounded. Pull the shoulders forward and towards each other as the back is rounded to form a bow with the shoulder girdle. Looking down from above, the arms should look like they are embracing a large barrel.
Repeat steps 1 through 3. Pay close attention to the changes in the sensations in your body as you work through seach step. If you bounce up and down lightly in the position in Step 3., the angles of the joints in your stance should return to the static preload position after every bounce.
With the ski boot and Zeppa-Delta ramp angles configured to enable an SR stance, your ski boots will work for you and with you instead of the other way around.
In my next post, I will go into greater detail on how rounding the shoulders and holding the arms in the correct position optimally activates the muscles associated with the SR stance.