A soon to be published study (1.) recognizes that recent advances in sensor-technology allow the kinematics and kinetics of skiing to be monitored and data collected during training and actual competitions. The data will generate detailed information about the biomechanical factors related to success in competition and used to individualize training and skiing and equipment for each unique skier and, most important, motivate innovative scientific research for years to come.
Individualize equipment for each unique skier
I fervently hope that this marks the beginning of the realization of a vision I had 30 years ago; one that resulted in the 1992 on snow studies using a unique instrumented research vehicle I designed with a biomedical engineer. This research vehicle allowed data to be acquired from skiers ranging from World Cup and Olympic champions to neophytes during actual ski maneuvers and meaningful metrics generated with which to assess performance. The objective of the study was to validate my hypothetical model of the mechanics, neurobiomechanics and physics of platform balance and the mechanism of skier CNS mediated dynamic stability. A validated model is essential for the interpretation of performance extrapolated from data. The intent of the subsequent patents was to provide a knowledge base to serve as a foundation for a science that would eventually enable individual skier optimization of every aspect of equipment and make skiing as easy and intuitive as walking for the masses.
A major source of inspiration and direction for my work and especially for my persistence came from the medical text-book The Shoe and Sport, in particular, Part 6 The Ski Boot.
From a technical (skiing) point of view, the ski boot must represent an interface between the human body and the ski. This implies first of all an exchange of steering function, i.e., the skier must be able to steer as well as possible, but must also have a direct (neural) feedback from the ski and from the ground (snow). In this way, the skier can adapt to the requirements of the skiing surface and snow conditions. These conditions can be met if the height, stiffness, angle and functions (rotational axes, ankle joint (AJ)/shaft) of the shaft are adapted, as well as possible to the individual skier.
The modern ski boot must be designed from a functional point of view, i.e., the design must take into consideration the realities of functional anatomy (axes etc.).
It (the design) should not make compromises at the expense of other joints (length of shaft, flexibility and positioning).
It (the ski boot) must represent the ideal connecting link between man and ski (steering and feedback).
I am forever indebted to Dr. E. Stussi, Member of GOTS – Chief of Biomechanical Laboratory ETH, Zurich, Switzerland, Professor Dr. M. Pfeiffer of the Institute for the Athletic Science, University of Salzburg, Salzburg, Austria, Dr. med. H.W. Bar, Orthopedics-Sportsmedicine, member of GOTS, Murnau, West Germany and W Hauser and P. Schaff of the Technical Surveillance Association, Munich, West Germany and other pioneers who inspired my efforts and paved the way to the future of skiing.
In the words of W Hauser and P. Schaff:
In the future, ski boots will be designed rationally and according to the increasing requirements of the ski performance target groups.
I sincerely hope that the work of Supej Matej and H-C Holmberg (1.) ushers in the future of skiing.
The Platform Balance Solution
In previous posts I established that:
- the axis of rotation of the foot and the ski (steering) resulting from rotation of the femur in the socket of its ball joint with the pelvis by what amounts to a muscle driven torque motor, occurs behind the center of the long running surface of the base of the ski.
- the ball of the foot of a skier is located on the proximate center of the long running surface of the base of the ski.
- edging and carving force require components of force with vectors aligned 180 and 90 degrees to the transverse aspect of the base plane of the outside ski.
- the rotational or steering force (torque) is the source of the vector of the 180 degree force acting into the snow.
- the point of application of the rotational cutting force when the axis of rotation of the ankle is oriented on the X-Y axis of the ski is mechanically ineffective. The monoplanar nature of the torque makes it less effective in terms of contributing to skier dynamic stability.
- the effect of side-cut on platform angle mechanics must also be considered.
From a mechanical-neurobiomechanical perspective, the logical place to apply the center of force of the foot acting 90 degrees (or slightly less) to the transverse base plane is under the ball of the foot (i.e. the head of the first metatarsal).
After a thorough investigation and analysis of the forces associated with platform angle mechanics I reached the conclusion that given the robust structure and the degree of stability of the head of the first metatarsal and the fact that the 90 and 180 degree forces should be congruent it seemed logical to apply the force acting 180 degrees to the transverse base plane of the ski to the medial aspect of the head of the first metatarsal. The 1992 study was designed to confirm or disprove the validity of this conclusion.
he graphic below shows the application of the rotational (steering) force to the medial aspect of the head of the first metatarsal.The photo below shows the robust force transfer structures under and on the inner (media) aspect of the head of the first metatarsal.
In my next post I will discuss the requirements of a ski boot necessary for the user to simultaneously apply plantar force to the platform and rotational force to the medial aspect of the head of the first metatarsal.
- Recent Kinematics and Kinetic Advances in Olympic Alpine Skiing: Pyeonchang and Beyond – Supej Matej and H-C Holmberg: Frontiers in Physiology