Steve, great discussion … for debate. Ahhhh, the ever recurring bootfitter metatarsal spread debate for which I offer food for contradiction. First off, I think we are really talking about the first metatarsals for which toe spread would be a product of. It seems to me that much of the typical mechanics associated with a foot strike during a normal walking gait are factors that we depend on the boot to lock up for stability and especially as our movements are meant to “transfer” through the boot and not “expire” within as would foot spread. As an example that some may be more familiar with, the ankle sees as much as 18% inversion and eversion in a barefoot gait where a race boot may only allow 3 - 5 degrees of that lateral ankle flexion (for inside the boot ankle tipping for lateral boot leverage). A ski boot is an “unnatural” support of the foot that “is” the limitation of its natural movement for which, otherwise, there would be no support.
From all those who I have read who have written about foot/toe/metatarsal spread in ski boots have come from a podiatric perspective, a discipline from which the ski boot has never been significantly scientifically supported. We forget that feet are not “feet” when they are in ski boots. Because the skis are functional extension of our feet, they ARE our feet when skiing and where the normal “bio” mechanics of the foot are highly skewed. Functionally, the boot acts as a bio-organic exoskeleton which represents a complete shift in the entire matrix of the mechanics involved. As an example, pressure under the sole of the foot moves in “opposite” direction between a walking gait and turn cycle and where foot spread “would” reside at opposite ends of said gait/cycle. Regardless, it seems that metatarsal spread is more associated with significant ball to toe flexion in a walking gait that does not occur inside the ski boot. When we stand on our bare feet, as if in ski boots, and transfer pressure from ball to heel and back without flexing it at the ball as in a walking gait, there is very little, if any, spread anyway. If my metatarsals were allowed to spread inside the boot, I don’t feel I would have the same lateral stability that I need to tip the ski aggressively back and forth. To me, metatarsal spread would also represent an unnecessary delay in transmitting pressure to the shovel of the ski.
When it comes to “both” biomechanics and ski technique, mobility and stability tend to be mutually exclusive properties where more stability never offers more mobility and vice versa. So, in this case, I don’t believe that this metatarsal spread “mobility” would offer any attribute of stability and, more likely, would do the opposite. If the actual argument is that the extra “width” itself offered by spread is what gives stability, I believe that difference is much too negligible to make any difference (single digit percentage) as well as a dynamic that would be eclipsed by the width of the ski - our “real” foot when skiing. The ultimate characteristics of a ski boot widdle down to movement allowed vs movement disallowed where the disallowance is as important, if not more, than the allowance. In other words, we could ski in a boot that offered no foot mobility at all much better than in a boot that instead offered no support at all.
There is further evidence that dysfunctional levels of arch collapse and flat feet are associated with foot spread. Foot/toe spread even for walking may not be considered ideal: Copied from Regenexx Orthopedics site:
“The forefoot (or the distal portion of the foot, where the toes live) houses a band of tissue called the transverse metatarsal ligament. This ligament runs across the forefoot and not only connects the five metatarsal bones (the bones that form the toes at the end) but holds them nice and tight, providing just the right amount of firm flexibility to provide proper walking motion in the foot. When there is a problem with this ligament (e.g., the ligament has become lax, or loose) the forefoot can become unstable.
The foot, as you will see in my brief video above, angles a bit as you walk, so you need a firm foundation of support in the forefoot to allow that to happen. This also stores and releases energy, giving you “spring” in your step. This is why the transverse metatarsal ligaments (along with the supporting muscles) are so critical here.
Unfortunately, when the transverse metatarsal ligament in the foot becomes loose, this can not only disrupt walking and create more problems in the foot, it can also impact other musculoskeletal structures all the way up the entire lower limb, from the ankle to the knee to the hip. This happens because the energy that was supposed to be absorbed by the stable forefoot and tight metatarsal ligament instead get transferred up the kinetic chain (to the next joint or joints up). Similarly, if the forefoot is unstable, this can cause too much motion at the ankle, knee, and hip as the foot caves inward as it hits the ground.
One sign of this instability in the forefoot is toes that spread apart when walking as the ligament is no longer firm enough to hold the metatarsals tightly together. This is a sure sign of a “mushy” foot that can’t absorb forces or help stabilize the ankle, knee, and hip. Let’s take a look at the forefoot of one of my patients and compare his normal forefoot on one side to his abnormal one on the opposite side.”
Also, in regards to continual dorsiflexion, if that means no trade off with plantar flexion, I wouldn’t advocate that “stance”.