THE SKIER BALANCE ‘SIGNATURE’


Since the number of followers of my blog with a technical background is increasing, it is timely for me to review the studies done 1991 with the Birdcage research vehicle and the content and purpose of the subsequent patents awarded to me based on the findings of those studies.

For those who are not aware of the Birdcage, it was a sophisticated research vehicle I designed with a biomedical engineer. The Birdcage replaced the conventional ski boot and allowed studies to be done during actual ski maneuvers that controlled variables. Most important, the Birdcage minimized ‘spurious background neural noise’ resulting from interference with the physiological function of the lower limbs caused by the ‘indiscriminate envelopment’ of the structures of the foot and leg by the constraining structures of the conventional ski boot. This spurious background neural noise makes it impossible to state with any degree of certainty how a ski boot affects the physiologic function of a user, let alone arrive at any meaningful conclusions. For this reason,  ‘neural noise’ makes it impossible to state with any degree of certainty how custom insoles or boot-fitting interventions such form fitting-constraint systems affect the physiologic function of the user during actual ski maneuvers. This issue was recognized by University of Ottawa foot pressure studies which acknowledged that equipment variations such as ski boot differences and the fact that some subjects wore custom designed footbeds, while the other did not, may have affected in-boot measurements.

Those who attempt to perform studies of physiologic function during actual ski maneuvers or develop technologies designed to coordinate the physiologic events associated with sound ski technique, will be frustrated by the presence of spurious background neural noise. My hypothesis, that the Birdcage studies were designed to validate or invalidate, was that under certain conditions of constraint, a specific sequence of events representing what amounts to the Balance Signature seen in gait studies would be observed and that the resulting Balance Signature could be formulated and applied to technologies such as training software. The findings of the Birdcage studies indicated that, within certain limits, the CNS could successfully negotiate a balance-solution with source of GRF supplied by the snow (GRF). The problem is that the structures of the conventional ski boot intentionally interfere with this process.

A recent study (1) on the arch spring serves to illustrate how the use of a novel insole technique can study the effects of arch supports and prescription orthotics on the energy sparing mechanism of the intrinsic spring of the arch.

In anticipation  that there would be little or no interest in the Birdcages studies, I embedded the findings in US Patent 5,265,350 when I wrote it in 1992. My intent was to create a historical record in the public domain in the hope that the knowledge contained in the document would be found and put into practice in the future. Once the legalese is extracted, the patent presents a detailed road map describing the constraining environment in which the physiologic function associated with the Balance Signature can occur.

An editable version of text of the US Patent 5,265,350 can be downloaded from the US Patent Office web site. The patent document, with figures, can be downloaded from the Google Patent site.


  1. The Foot’s Arch and the Energetics of Human Locomotion – http://www.nature.com/articles/srep19403