When I first saw a pair of iRi’s I thought to myself (and I’m probably not the only one who did): “How can those clunky shoes be comfortable??” How wrong I was! They turned out to be practical, stylish and healing; they optimize the way I walk; my posture, my stride, and my muscle efficiency. Here’s how:

What’s unique about the iRi shoe lies within the statement-making “shark-tooth” sole. In fact, when analyzed using a gait scanner (report attached), the funky EVA sole acts as a metatarsal head rocker, similar to the rocker-bottom sole initially popularized by the German design of the MBTs (Masai Barefoot Technology). iRi’s are not just another rocker-bottom shoe. The gait analysis demonstrates a cushioned heel strike followed by evenly dissipated midfoot to forefoot pressures. On the gait analysis the midfoot contact pressure ranged from “green” to “yellow” level throughout with minimal “red” or high pressure areas.

The unique iRi rocker technology helps forward progression of the tibia over the ankle joint without sacrificing balance because the center of gravity remains unaltered. The center of gravity remains unaltered because the iRi sole does not include a heel or Lisfranc joint rocker. Thus iRi’s are useful if there is any arthritis of the ankle or a tight Achilles tendon limiting ankle dorsiflexion. Based on the gait analysis, the apex of the iRi rocker is right posterior to the metatarsal heads, creating a smoother walk with a faster transition to the forefoot. This rocker architecture has been shown to reduce midfoot and longitudinal arch pressure in the foot attributed to plantar fasciosis, as well as forefoot plantar pressure. Now that’s double optimization!

Let’s talk biomechanics of the gait cycle with iRi shoes. We begin with arguably the most important part- initial contact phase. Normal gait at this point shows the hip is flexed, knee is extended, and ankle is neutral. With a cushioned yet firm heel the iRi’s reduce the stress or
vertical impact force on the heel bone and all the way up the chain to the other weight bearing joints; knees and lower back. The contact phase of gait coincides with maximum shock absorption and the point at which our feet take on our body weight. Thus the iRi’s may help prevent stress fractures in the heel (calcaneus) and tibia (which often present as shin splints).

The next phase of gait is midstance. During normal midstance, the hip and knee is extended while the ankle is flexed. With the iRi’s there is slightly increased flexion at the hip, knee, and ankle during midstance. This increased flexion assists the metatarsal rocker to lift the heel and propulse the foot to toe-off before swing, analogous to barefoot locomotion. Thus the iRi’s may also help reduce pain associated with midfoot and forefoot arthritis (conditions with restricted joint motion), i.e. hallux rigidus/limitus, rheumatoid arthritis, gout and gouty arthropathy, and congenital midfoot coalitions. Due to the flexible neoprene upper, iRi shoes could also accommodate a number of other foot deformities, including but not limited to hallux abductovalgus or bunion deformity, and sagittal plane deformities such as hammertoes, mallet toes, and claw toes. The flexibility of the material does not restrict the inflamed soft tissues associated with these bony deformities resulting in pain relief.

During the swing phase of gait, iRi’s cause a slight increase in ankle dorsiflexion. This is obtained by the increased activation of the tibialis anterior tendon. The small intrinsic muscles in the feet are also activated during this phase at a higher rate resulting in reduced lower back joint loading and knee adduction. Thus the iRi’s may help prevent or slow down the progression medial compartment knee osteoarthritis and lumbosacral osteoarthritis (associated with chronic low back pain). Taking into account the minimal heel drop in the iRi shoe, about 8 mm, the Achilles tendon stays activated throughout much of the gait cycle, especially swing. Activation of the Achilles tendon leads to balance training during normal ambulation. This drop is optimal compared to a zero drop heel found in minimalist shoes where strain on the Achilles is excessive for walking longer distances or traditional drop heels (over 10mm) which contract or shorten the Achilles over time.

The iRis are not recommended for people who have reduced balance such as older people who have trouble walking or walk with assistive devices because due to the metatarsal rocker there is a shorter midstance phase (where there is double limb support) compared to normal gait. It is important to be aware of the fact that ankle eversion and inversion (frontal plane motion) is increased during midstance with iRi shoes partially attributed to the flexible upper material. Some people may have difficulty getting used to an optimized gait pattern induced by the iRis thus it is recommended to break in the shoes by wearing them for about two hours the first day and increasing every day by two hour increments until a full eight hour day is reached.

In the concrete jungle of the city where the average New Yorker walks 3 miles a day, a shoe that is biomechanically sound, stylish, and practical is hard to find- heck, it’s priceless! iRi’s may help minimize stress on the feet, ankles, knees, and lower back. The iRi upper is also practical in rainy NYC weather and flexible enough to accomodate common foot deformities such as bunions and hammertoes that often otherwise require an ugly wide toe-box orthopedic shoe. From initial foot contact with the ground to your last step in the iRis, this shoe is structurally built to optimize your gait, alignment, and posture.

References:
Mokhtar Arzpour, Stephen W Hutchins, Farhad T Ghomshe, et al (2013) Effects of theheel-to-toe rocker sole on walking in able-bodied persons. Prosthetics and Orthotics International.
Scott Landry, PhD. Unstable shoe designs: Functional implications (2011) Lower Extremity Review
Greg Gargiulo (2017) Rocker-bottom footwear: effects on balance, gait Lower Extremity Review Lin S-Y, Su P-F, Chung C-H, Hsia C-C, Chang C-H (2017) Stiffness Effects in Rocker-Soled
Shoes: Biomechanical Implications.
Preece, S.J., Chapman, J.D., Braunstein, B. et al. (2017) Optimisation of rocker sole footwear for prevention of first plantar ulcer: comparison of group-optimised and individually-selected footwear designs. J Foot Ankle Res