Muscular contractions
Muscle contraction is the process in which muscles are shortened due to a stimulus. Our motor neurons (neurons that command muscle contractions) activate whenever impulses are transmitted, otherwise, muscles remain relaxed. As muscles contain a variety of receptors reporting different data like tension level, movement speed, and the position in where they are located related to joints, our brain requires this information to guide our body through smooth and balanced movements, maintaining posture while adapting to the environment.
Muscle contractions are divided into voluntary, which are all made by our will and involuntary (controlled by the central nervous system) such as heartbeat, coughing, hiccups or breathing.
Muscle functioning
Muscles wrap our body as an elasticized cover and when contracting, they make it reduce in size, restricting space for movements’ execution. Each muscle that is active (agonist) has another one opposed to (antagonist) and by each muscle that is relaxed, another one is contracted.
Our motor cortex determines which muscles must contract or relax and the amount of effort they must create. This is done via certain programs, i.e., a set of signals informing about when and how to activate. As an example, our upper leg muscles move the muscles in the lower section: thigh moves the lower part of our leg and this part moves our feet.
Muscle contractions also can be generated by vibrations that, stimulating muscle sensory endings, cause a stretching reflex (Berthoz, 2013). Without elongating after skiing, muscles remain contracted, restricting our movement possibilities.
Influence of muscle contractions in trunk stabilization
Maintaining a balanced upper body is one of our goals when skiing. To attain this there are two mechanisms: slow-twitch mode (muscle tone), which serves to stabilize our upper body, and fast-twitch mode used for upper body motion. This is achieved through the actions of dorsal muscles (spine extensors) and abdominal muscles (spine flexors).
Efficient effort
One aspect of being skiing efficiently is to recognize how to graduate our muscle effort. What differentiates an evolved skier is the economy of muscle exertion. In non-evolved skiers, the use of excessive muscular effort tends to replace technique. To learn how to perform movements we tend, initially, to utilize more effort than required, slowing our learning process and leading to premature fatigue.
According to the Feldenkrais Method, the purpose of action performance is to organize our body to operate with minimum effort and maximum efficiency. In this sense, we should pursue muscle de-contraction, starting by identifying and reducing muscle activity levels, in order to consume a reduced amount of energy and becoming less fatigued.
We generally recourse to constant muscle effort at maintaining balance, when actually we should aim to the conscious reduction of this effort. Efficient activity is characterized by minor movements of body parts up to simple local changes in muscle tone (Foley, 2009).
The principle of minimum effort
The Principle of least effort, also known as least resistance path, Law of no resistance or Principle of least action, is a theory that postulates that we naturally tend to choose minus effort in the activity we are achieving. According to this, our brain is encoded to carry out activities minimizing energy expenditure, which is normally observed in the expert skier thanks to his proficiency. This principle could be applied in our movements and actions coordination to obtain the most economical and comfortable skiing as possible.
Motor execution and effort
In motor execution, our effort is the activity generator as “action force” which is our capacity to produce changes. It is an important factor that we must learn to regulate by being aware of how much effort we generate, maintain or eliminate. Not releasing energy excesses leads to repeatedly muscular tensions, confusing a punctual effort with constant muscular tension.
Advanced skiers take advantage of the generated effort while beginners suffer the excess of it. Effort is diluted when we perform inefficient movements or not transferring our impulses correctly from one body segment to another, interrupting the kinetic chain.
Taking the skis’ spatial position as a reference, being advanced skiers, we apply effort in a proximal to distal mode, i.e., starting at our feet (the proximal body part to the skis) and extending it to our upper body (the most distant part). In beginner skiers, we observe that this application is distal to proximal since their effort tends to be generated from the upper body down to their feet.
In relation to the turning effort (steering action), it should be generated at the start of the turn to redirecting it at the final phase towards the next direction change. It is common to retain momentum up to the very end of the turn by muscle tension but it is more efficient releasing it at a suitable instant to link the next direction change.
While in motion and due to external forces, our body accumulates potential energy, which hampers body displacement if we fail to orient it towards the center of the next curve by ‘removing the brakes’, as Feldenkrais says.
Effort and the Weber-Fechner Law
The Weber-Fechner Law is the psychophysics law establishing the relationship between stimulus and perception based on Weber’s sensation law. If we apply it into skiing, the less the muscular tension, the greater will be our movements’ sensitivity, or said in a different way, the least the effort, the higher the precision in perceiving muscle responses.
Proper muscular use
As it was stated, deep muscles are the ones located on the very inside of our body; in the abdomen, back and buttocks, serving for greater efforts. Peripheral muscles are found in our body’s periphery and are intended for fine tuning executions. When skiing, we should use hips’ and legs’ deep muscles to give strength, leaving feet muscles for sensitivity related to turning and fine edging.
Skiing is then easier if our bodies’ center muscles are employed and our limbs’ muscles are activated to guide our bones. An expert skier has better use of pelvic muscles (buttocks, thighs, abdomen), which are the strongest muscles; obtaining that all his effort is transformed into movement. The beginner, on the other hand, tends to use almost all muscles, especially the lumbar muscles which are quickly activated; this may be the reason for displaying a constant upright posture.
An incorrect feet support modifies our bones position, requiring additional muscular efforts. Then, when muscle tension becomes excessive, we cannot differentiate proper motor behavior, nor can it ensure an effective connection with the snow or appropriately orient our motions.
