Imbalances
Skiing means disturbing our balance permanently to then restore it in constant alternation between balance and imbalances. To attain this, we must liberate our structured and rigid balanced posture to experience flexible balance sensations. It can be said that we are continuously in search of balance in our imbalance (Foissy, 2011).
When displacing our BoS or our CoM, we find ourselves in an imbalanced state. Our body segments dismantle upwards from feet to head in a bottom-up process. The imbalance spread causes temporary restrictions which are decisive for the ability to rebalance (Le Goïc, 2013).
An imbalance causes muscle contractions which in turn hinders rebalancing due to the stiffness produced. According to LeGoic (2013), the failure of rebalancing mechanisms could be placed at:
- A sensory deficit level in detecting the imbalance.
- The selection of the response.
- According to the decision criteria we adopt.
- The response preparation.
- The delay and form of the execution. It is generally observed that the beginner rejects imbalance while the expert accepts it and takes advantage of it.
Fore-aft imbalances
We have defined that skiing is experiencing constant imbalances. Aft imbalances are constantly suffered by the beginner during the first slides, while the expert skier exploits fore imbalances, allowing a better control at turn initiation or bumps absorption by locating the CoP (center of pressure) in the front part of his feet. In other words, experienced skiers seek imbalance by displacing their bodies forward to take advantage of skis geometry and to benefit or counteract external forces.
Skiing is an activity based on pursuing balance while sliding on an inclined surface, causing our predisposition to a certain state of alert due to our fear of falling. Losing equilibrium and falling is part of skiing.
Falls are produced by the association of two conditions: the initial loss of balance and our failure mechanisms of rebalancing. The rebalance capacity will depend on if falling is avoided or not (Le Goïc, 2013).
Our inherent fear of falling will limit oscillations amplitude proper to skiing and this will take form us greater energy expenditure by muscle tensions oriented to constrain such oscillations.
A deficit of postural adjustments to compensate imbalances is what makes the person particularly sensible to falls in situations of instability (Le Goïc, 2013).
Factors inducing falling
The causes of falls in skiing are varied and complex, and a critical factor is the capacity of responding effectively to a balance loss (Maky & McIlroy, 1999).
We can define two types of factors that cause falling: internal factors related to motor behavior and our mental and emotional state at the time prior to the fall; and the external factors depending on environmental conditions.
Internal factors could be:
- Our insufficient capacity to react to a balance loss, including the absence of a decision to execute rebalancing movements.
- Our sliding susceptibility, lack of attention and neglect, fright or fear, and recklessness.
- Our distorted perception of risks and our skills.
- Breathing disturbance is also a component that tends to trigger the sensation of falling since our stomach contracts and we cannot breathe properly.
In terms of biomechanical factors, we observe the following:
- Improper posture.
- Exaggerated movement of our head or trunk including arms.
- Mobility alteration or deficit.
- Muscle weakness to compensate balance perturbations.
- Insufficient control of the CoM displacement.
- Rebalancing resistance caused by muscle stiffness because of joints amplitude reduction and overreacted hips extension (hip hyperextension).
In relation to sensory factors, balance loss is occasionally associated with sensory information contradiction (vision, proprioception, joint, and muscle receptors), which the brain fails to process.
Direction of falls
The most common falling direction in skiing is the typical backward fall because of an unexpected slide or perhaps due to the apprehension of the spatial emptiness occurring while facing the slope.
In expert levels, forward falls are common while skiing powder or moguls. Lateral falls are also observed, possibly because of weakness or inability of the non-dominant foot or leg.
The sensorial sequence involved in falls
When we experience a perturbation causing a fall, we tend to react based on a sensory information sequence. Usually, tactile and proprioceptive information will be available first on successive stretches of foot/leg, leg/thigh, thigh/trunk or trunk/head, and vestibular and visual information will be the last to indicate the fall.
