Ramp sole angle or drop, as it is called when the heel is elevated above the forefoot in footwear, affects the function of not just the foot, but the entire muscle-skeletal and balance systems.
With few, exceptions, the sole structure of most shoes elevates the heel above the forefoot. Prolonged activity in footwear with anything other than minimal drop will result in chronic contraction and shortening of the muscles in the backs of the lower leg.
“This is an extremely serious situation considering the fact that the shortened lower leg muscles are now contributing to faulty foot function in a number of ways. The most significant foot fault caused by elevated heels is that shortened posterior leg muscles pull improperly on the back of the heel (Achilles tendon) to unnaturally increase the amount of flattening the arch will undergo. Said another way, chronically shortened lower leg muscles increase pronation of the foot and ankle.
“A more significant and potentially debilitating effect of heel elevation is that there is an involuntary stretch reflex built into the posterior lower leg, that can only be activated if the heel is allowed to come close to the ground. This does not occur in most shoes available to consumers today, EVEN amongst athletic models”. – Northwest Foot & Ankle (nwfootankle.com)
“Barefoot, the perpendicular line of the straight body column creates a ninety degree angle with the floor. On a two-inch heel, were the body a rigid column and forced to tilt forward, the angle would be reduced to seventy degrees, and to fifty-five degrees on a three-inch heel. Thus, for the body to maintain an erect position, a whole series of joint adjustments (ankle, knee, hip, spine, head) are required to regain and retain the erect stance.
“In this reflex adjustment scores of body parts — bones, ligaments and joints, muscles and tendons — head to foot must instantly change position.
“But shoe heels have other, lesser-known influences on gait. For example, any heel, low to high, requires a compensatory alteration or forward slant on the last, which is translated to the shoe. This slant is known as the “heel wedge angle.” This is the slope or slant of the heel seat, rear to front, to compensate for the shoe heel height. The higher the heel, the greater the angle.
“On the bare foot there is no wedge angle. The bottom of the heel is on a level one hundred and eighty degrees, with body weight shared equally between heel and ball. Inside the heeled shoe, the wedge angle shifts body weight forward so that on a low heel body weight is shared forty percent heel, sixty percent ball; and on a high heel ninety percent ball and ten percent heel.
“Let’s add one further influence of shoe heels, low to high. The shoe’s elevated heel shortens the Achilles tendon and accompanying shortening of the calf muscles.” – Dr William A. Rossi, DPM. ‘Why Shoes Make ‘Normal’ Gait Impossible’ – Podiatry Management. March 1999.
Katy Bownman also talks extensively about the adverse effects of heel lift in her book Whole Body Barefoot: Transitioning Well to Minimal Footwear.
The reason I started this blog on May 11, 2013 with my first post, A Cinderella Story: The ‘Myth’ of the Perfect Fit – https://skimoves.me/2013/05/11/the-myth-of-the-…sive-perfect-fit/, was because a number of issues in my mind were still nebulous. Even though my boot modification efforts over several decades had consistently met with success at the highest levels of Olympic and World Cup competition, I still had more questions than answers. I knew that I was close. But I did not yet have the big picture figured out. One question that remained unanswered was, is it possible to develop a formula for setting up the boot/binding/ski system that will consistently maximise skier/racer performance? One thing I was certain was critical to any formula is the angle of the ramp the skier stands on in relation to the surface of the snow under the base of the ski.
Since 1978, I had known that a combined ski boot boot board/binding ramp angle (Net Ramp Angle) of about 3 degrees was critical to the development of a strong stance and that the positive effects of ramp angle fell off dramatically at NRAs of more than 3 degrees. I had a hunch that less NRA than 3 degrees allowed a stronger stance. But I didn’t know the NRA optimal range and especially where the bottom end was at which NRA became too low.
When I designed the Birdcage in 1991 with a biomedical engineer, we made two sizes. The small size fit US men’s 4 to 8 feet. The base ramp angle was 2.5 degrees. The large size fit US men’s size 8 to 12 feet. The base ramp angle 2.35 degrees. The ramp angles were based on our theory that it was better to be on the low side of optimal than on the high side. We were hedging our bets by playing what we thought were the low and high ends of the optimal range with 2.35 and 2.50 degree ramp angles. The robust adjustment range of the Birdcage made it possible for skiers with up to size 8 US men’s feet to ski in both the small and large versions. This made it possible for some testers to compare the 2 different ramp angles.
For those of you who are not familiar with the Birdcage experiments, the links below are to 4 posts on the Birdcage in the order of first to last.
EPICSKI ARTICLE – THE BIRDCAGE EXPERIMENTS
THE BIRDCAGE DATA – WORLD PREMIER
THE BIRDCAGE EXPERIMENTS – DATA 3
BIRDCAGE VS. CONVENTIONAL
The Effect of Heel Lift or Ramp
Elevating the heel above the forefoot more than a small amount, tips the whole body forward. This provokes a compensatory balance response that alters the default angles of the ankle, knee and hip joints and the lengths of the associated muscles. This can dramatically affect the functional integrity of the foot and compromise the effectiveness of the balance system. That elevating the heel affects everyone in this manner is a virtual certainty.
Past a certain point, NRA in the stack of ski equipment between the sole of the foot and the surface of the snow will force a skier to retreat to weight borne on the heel with support for the leg from the rear of the boot shaft for stability.
After a lot of experimentation last season and input from reliable sources in Europe I reached a tentative conclusion that the optimal Net Ramp Angle is in a range between 2.5 to 2.7 degrees. But nothing is really ever settled. A complicating factor is wearing shoes with varying degrees of drop. This prevents the balance system from using the default barefoot, zero drop balance reference or developing a consistent balance reference based on a fixed drop. Further exacberbating the effect of Net Ramp Angle is that boot boards are seldom monoplanar (dead flat in the x – y planes.
In my next post I will discuss the factors that add to and complicate the effects of Net Ramp Angle and my vision for a standard boot board ramp that would serve a ski stance/balance reference and a starting point for Net Ramp Angle Optimization.