INJURY PREVENTION

THE IMPACT OF BIOMECHANICS ON THE PERFORMANCE

AND INJURY MANAGEMENT OF THE SKIER

By Sophie Cox BSc (Podiatry), SRCh, MChS

BIOMECHANICS OF SKIING Skiing is a series of closed kinetic chain rotations and movements which allow for the setting and un-setting of the ski edge to ini- tiate and complete turns over varying surfaces (1). In order to identify the mechanism of an overuse injury, or the aetiological factor of the skier’s problem with their technique, knowledge of the biomechanics of skiing is vital.

The three phases of the ski turn are: 1) Lead change from downhill to uphill ski 2) Turn initiation 3) Deceleration/power absorption.

Skiers make up a large proportion of the sporting population with over 200 million people worldwide participating in the sport. Until now the three crucial elements of snow sports - equipment, instruction and medical well-being, have been separate entities offered en-masse to the thousands of clients that pass through ski resorts each week throughout the ski season.

However, although three people may appear to have the same problem of edging the ski, the reason for their problems may all be very different. One skier may have badly fitting ski boots, the second may be applying pressure to the wrong part of the ski at the wrong time, while the third could be nursing an unknown biomechanical injury and compensating through bad technique. As an injured skier, or a skier that has plateaued in skiing ability, it is important to address all three areas to truly establish the root of the problem.

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1. Lead change During lead change, ankle extension of the new downhill leg occurs with forward movement of the hip to bring the centre of mass forward. The upper body should be slightly flexed forwards and weight transfer takes place to the new downhill leg.

2. Turn initiation Turn initiation then follows with sub-talar joint pronation result- ing in a valgus knee position due to medial axial rotation of the tibia that accompanies eversion of the calcaneus during prona- tion. Loading of the first metatarso-phalangeal joint takes place as the ski is put on edge and the upper body is in counter- rotation for balance.

3. Deceleration/power absorption The final phase of the ski turn, deceleration/power absorption is where the energy created by the fall-line is absorbed by flexion of the ankles, knees and hips in preparation for the next lead change phase.

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