Is there room for a new vision of physical qualities ?
Traditionally, it has been said that there are four physical qualities: strength, endurance, speed and flexibility. All of them are at the same level of importance and with a degree of interaction that is very small or non-existing. Currently, the large amount of information available and the progress in the sport science field, makes me consider that there can be another model that is more updated and closer to our current working reality. Next, you can find my vision about the physical qualities.
I would like to reflect about the origin of each physical quality from a mechanical point of view to simplify the matter (although the energetic system and nervous system are also involved in this process). If I think about the most basic element, the origin of everything, I can tell that we produce the movement due to the muscle fibers contraction. As a consequence, based on this vision, the strength can be defined as the capacity of muscle fibers to generate force. The endurance could be defined as the capacity of the muscle fibers to work during a certain time, and the speed as the capacity of the muscle fibers to contract and relax in the fastest way possible.
If these definitions are true, I could say that the muscle contraction is at the origin of these three qualities and therefore the main movement axis.
I call ‘mechanical qualities’ the strength, endurance and speed, since they are in charge of movement production, however each one of them has a different role. From my point of view, the strength is the main physical quality, principally for its importance as protective element in the system in the face of internal and external forces, as well as for its large influence in the development of speed and endurance as physical qualities. As you can see in figure 1, from my point of view, the strength would encompass the speed and endurance, being both at the same level, but having a secondary role, considering that, they have a specialization quality to contract and relax as fast as possible and the quality to endure during a certain time. I consider that these three physical qualities are sport specific, meaning that their influence in this model would change, increasing or decreasing its importance, but they would never change their role. The strength would always be the essential physical quality.
However, where is the flexibility? To be honest I do not like the word flexibility, meaning capable of being bent, without breaking, considering that makes reference to a passive quality of the tissue (there is not conscious neuro-muscular activity), and it is less valuable in the prevention and performance fields, therefore it does not make much sense to include it in this model. Instead, I prefer to make reference to mobility, intended as the neuro-muscular capacity to control active range of motion (motor cortex activity). I include mobility in another type of qualities that are different from mechanical, qualities that I call functional qualities. Along with mobility, these include joint stability and motor control (Figure 4).
These three qualities are closely related to each other, having a constant communication, knowing that they need each other to accomplish their function correctly, which is to keep a functional balance, and as a result , allow the movement production.
But what is motor control exactly? It is the process by which humans and animals use their brain to activate and coordinate the muscles and limbs involved in the performance of a motor skill (Figure 2). Fundamentally, it is the integration of sensory information, both about the world and the current state of the body (Wise et al 2002). Therefore, we are talking about different integrated systems to produce movement on the one hand, and keeping the functional balance at the joint complexes on the other hand. We are talking about central nervous system, muscular system and sensory system (part of nervous system).
I consider especially important the sensory integration and its relation with joint stability. Principally, we are talking about proprioception, that is regularly misinterpreted by connecting it exclusively with unstable surfaces. And then, what is propioception? According to McCloskey, it is the sensory information that contributes to the sense of position of self and movement (Figure 3).
Having said this, I would be more concern about being able to dissociate and control as many movement planes as possible in my joints, which would lead me to improving the adjustment of the movement, instead of focusing on external factors that perturb my sensory system without having a good control and functioning of my own body (movement, position, joints, etc.).
As I tried to explain, the nervous system along with the sensory part would regulate greatly the mobility and joint stability, with the main objective to produce movement without suffering any hurt in the system.
Integration: all in one
I would like to highlight that the central nervous system can limit the range of motion in a joint, if it considers that it can get damaged in that range, lack of joint stability, core instability or lack of neuro-muscular control in that range possible causes. Therefore, we should take into account this reasoning, before prescribing exclusively passive stretching to our players.
For this reason, I give importance to the relation and balance between mechanical and functional qualities (Figure 5). Moreover, it is necessary to look for that balance, otherwise we will create or increase dysfunctions, that it may leads to an increase of risk of injury. The following quote (I think from Michael Boyle) summarizes very well this concept.
¨Load on the top of the dysfunction = more dysfunction¨
On the other hand, it is common to focus excessively on the mechanical qualities (strength, speed, and endurance), trying to develop them in order to achieve a better performance, without assessing other elements in the system that also take part in the movement production. Very often, more is not better, because you are only as strong as your weakest link. Therefore, having an individual profile of the football player with his/her weaker links, is essential in order to prescribe effective exercises and improve movement quality, thus having an immediate positive effect in his/her health and performance.
¨You are only as strong as your weakest link¨
Key points and practical application
- Create individual profiles with their weak links to prescribe exercises accordingly.
- Find a time in the training schedule to perform daily individual exercise (to balance functional vs mechanical)
- Include prior to every training session:
- Core training (better with conscious activation and involving diaphragm)
- Mobility (active ROM)
- Include stability – motor control – proprioception work: Body awareness and dissociation, performing it slowly, actively and consciously.
- Kandel, E et al. Principles of Neural Science. 4ª Edition. McGraw-Hill Interamericana. 2000
- GUYTON, C.G. y HALL, J.E. Medical Phisiology. 11ª Edition. Elsevier, 2006.
- Timothy J.Suchomel et al. Review, The importance of Muscular Strength: Training Considerations, 2018
- Jeppe Bo Lauersen et al. Review, Strength training as superior, dose-dependent and safe prevention of acute and overuse sports injuries: a systematic review, qualitative analysis and meta-analysis, 2018
- Own elaboration: Influence from Julio Tous, Michael Boyle, Andreo Spina, Sergio Cañete.