What is SSI?

Shoe Stability Index (SSI) is an indicator of shoe stability, as an index. SSI is derived through mathematically combining the quantified measurements of midfoot stability (TCI) and hindfoot stability (VCI), indicating the shoe’s overall ability to control the motion of the foot.

What is TCI?

Torsion Control Index (TCI) is a measurement of midfoot shoe stability, in inch-pound units (in.-lbs.). TCI is measured through actively twisting a shoe around the longitudinal axis of the shoe, from the heel to the area of the toes joints, simulating rotational forces of the foot, and measuring the shoe’s resistance to this motion.

The higher the TCI, the firmer the midfoot and more torsional stability. The lower the TCI, the softer the midfoot and less torsional stability.

What is VCI?

Vertical Compression Index (VCI) is a measurement of hindfoot shoe stability, in millimeters (mm). VCI is measured through compression of the heel portion of the shoe under a fixed amount of pressure, thereby measuring how the structure of the shoe controls rearfoot motion.

The higher the VCI, the softer the midsole and less hindfoot stability. The lower the VCI, the firmer the midsole and more hindfoot stability.

What is Loaded Heel to Toe Drop?

Loaded Heel to Toe Drop is the measurement in millimeters of the height of the heel relative to the fore foot when compressed to a fixed poundage. This can be defined as vertical support.

What is RI?

Rebound Index (RI) is an indicator of energy return of shoe to the foot, in millimeters (mm). RI is measured through compression of the heel portion of the shoe under a fixed amount of pressure, and then determining how much force the shoe exerts on the foot.

Plantar Fascitis

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  • Heel pain with weight bearing
  • Tender medial aspect of plantar (bottom) surface of heel
  • Increased pain with running and walking activities

Possible Causes

  • Tight calf muscles
  • Excessive pronation
  • Weak intrinsic foot muscles
  • Soft, unstable shoes

Shoe Profile

The shoe midsole should provide maximum torsional stability to reduce medial foot rotation (pronation). Pronation stretches the plantar fascia, resulting in soreness and tenderness on the medial plantar (bottom) of the heel. A midsole with a high to medium heel-to-toe ratio may add further benefits by reducing tension on the calf and plantar fascia.


Neutral (mild pronators) – 3 mm heel lift with or without over the counter arch supports
Moderate to excessive pronators – Custom orthotics with 3 mm heel lift

Shoe Recommendations

The following shoes meet these criteria. Please click on the appropriate link to see the shoes and their OPIS data.

personal_male_2 personal_female_2

Recommended Accessories

SuperFeet arch supports

Provides increased arch support to reduce stress on the plantar fascia

ProStretch for calf muscles

Improves flexibility in the calf complex which reduces tension on the plantar fascia

Night Splint

Passively stretches the calf musclces while sleeping

Compression Socks

Provides compression & support to relieve pain in the heel and arch

ProTec Spiky Massage Ball

Great for massaging the arch & heel

The Stick

Effective way to massage the calf musle to reduce muscle tension & increase flexibility

SKLZ Cold Roller Ball

Provides targeted massage with ice therapy


**Please consult your physican before engaging in an exercise program.**

With all strengthening exercises, start with 3 sets of 10 repetitions. If you experience any sort of pain, reduce your reps to 3 sets of 5. For all stretches, repeat 3 times holding each stretch for 30 seconds to 1 minute. Using RICE (Rest, Ice, Compression, Elevation) can be beneficial in the treatment of injuries as well.

Gastrocnemius (calf) Standing Stretch
Soleus Standing Stretch
  1. Stand with hands resting on wall or on stable object.
  2. Place the UNINVOLVED leg forward of the involved leg.
  3. Keep the back leg (involved leg) straight and heel on the ground throughout the stretch.
  4. Lean forward bending at ankles and hold.
  5. Return to starting position, relax, and repeat.
  1. Stand with hands resting on wall or on stable object.
  2. Place the UNINVOLVED leg forward of involved leg.
  3. Keep heel on the ground throughout the exercise.
  4. Bend knees, squat down, and hold.
  5. Return to starting position, relax and repeat.
Toes Down Gripping Towel
Toes Down Pickups
  1. Sit in chair with foot resting on smooth surface with towel between foot and surface.
  2. Curl toes downward gripping towel on surface.
  3. Return to starting position and repeat.
  1. Sit in chair and place a wash cloth (or other objects) on the floor.
  2. With the toes and foot of the INVOLVED side, pick up the cloth and transfer to the opposite hand. If this is too difficult just bring the ankle up and inward.
  3. Repeat.

Images reproduced courtesy of T.E.D.© (Therapeutic Exercise Database) V. 2.0

October 2023 test data is now live!