Plantar receptors
Our feet are the connection with the snow, being considered as the primary sensory organs for balance control. As we have mentioned, our feet have 80% of the lower limbs sensory receptors, detecting support features, surface irregularity, pressure distribution, vibrations, and snow consistency. Our toes also play an important role in balance control.
Heels’ sensations influence fore-aft balance control while sensations from the anterior part of our feet (peroneals and tibialis anterior muscles) are more significant for controlling lateral balance. If we use our heels as a reference for plantar support, we will fail in the application of the anterior parts of our feet, which could be taken as references for lateral balance (1st and 5th metatarsal) as well as forward/backward balance control (metatarsals and calcaneus bones).
The information coming from our feet soles is fundamental for balance control, especially when our visual system is altered because of poor visibility conditions.
Additional balance references
For proper balance control, we need information that will be taken as references.
- Internal references are the projection of our CoM over our BoS (plantar sensitivity), the perception of body positioning (proprioception), and the maintenance of an upright posture (vestibular and visual system).
- External references include vertical (trees, buildings, and other people), horizontal (the horizon, a rooftop, slope signs or some horizontal upper parts of lift towers), and oblique references (slope inclination).
The importance of the upper body in balance control
In humans, two-thirds of the body mass is located at a two-thirds height of the ground (Winter, 1998). In the majority of skiing situations, our upper body serves as a stabilizing function while our limbs demand joint mobility. This works for the expert skier who knows how to control body oscillations, but the beginner not only has difficulty keeping his upper body stable; often he uses it as a turning component, causing greater destabilization.
The evolution of balance control
Our balance control evolution in skiing extends through several stages.
- At first, we adapted our usual upright posture on flat and adherent surfaces to a suitable stance on inclined and sliding ones.
- As balance control development evolves in a proximal-distal manner, initially we paid attention to our upper body and then to our hands and feet. This was confusing because, in our first glides, our attention was oriented exclusively to skis’ control.
- Then, in every technical gesture we performed, we experienced different balance sensations, and many situations of unexpected imbalances as starting in straight to snowplough descents, then from snowplough turns to half-snowplough/half-parallel (basic turns), until we reached full parallel turns performed at various amplitudes and speeds.
We were also particularly concerned about not falling and then, we were interested in developing our capacity to go from compensatory balance control (reactive) to proactive balance control (predictive). These anticipatory adjustments were acquired through many balance experiences during our technical evolution, which helped us adapt to more challenging terrain surfaces and inclinations.
As our balance is the most important feature to regulate when skiing, achieving a conscious control of our CoM took longer because of our oscillations. Also, due to the constant reactions of our sliding platform, we contracted agonist as well as antagonist’s muscles, making our stance not appropriate yet, and thus, affecting our balance directly. At that stage, we presented the typical image of a rookie in new motor activity, using a considerable amount of muscular effort in relation to the needed balance.
In our balance management, assuming that we are advanced skiers now, we can observe the following stages:
- In our beginner stage, we did not accept to compromise our balance so we acted according to our references and usual limits, avoiding imbalances.
- As intermediates, we risked our balance for short periods of time and maintained habitual balance references or could return to them during imbalances.
- As advanced skiers, we now experience balance in our imbalance, using external and internal forces to form a “balanced system”, organizing it by the effects and the forces we generate in our motions.
