STRENGTH EXPRESSIONS

In the previous entry we explained the great relevance of strength, since we can take it as the basic physical capacity on which the rest depend. This is so given that without the application of force, none of the remaining basic physical capacities (resistance, speed and flexibility (according to the classification of Blázquez Sánchez, 1993)) could take place. In this entry we will try to break down the strength in its different expressions, since it is a subject of vital importance when deciding the type of the objective to achieve with the training.

Weightlifting - Singapore competing by Julie V. CC BY 2.0

In the first place, we have to say that the expression of the strength depends on the following factors, as well as the combination between them:

-       Magnitude of the tension produced by the neuromuscular system.

-       Speed of displacement of the resistance.

-       Point of application of force.

-       Type of activation: eccentric, isometric, concentric or combined.

Once we have clear the factors that determine the different strength expressions, we have to say that there are different classifications in the literature, although almost all of them contain some basic structure. From this analysis, we present below the classification proposed by González Badillo & Ribas Serna (2002), with some relevant contribution by Tous Fajardo (1999):

-  "Absolute strength": corresponds to the theoretical potential capacity of strength, on which the muscular constitution depends, with factors such as the transversal section and the type of fibre. It is impossible to express it in a voluntary way, but it will only appear in extreme psychological situations, or with the help of drugs or electrostimulation.

-  "Maximum isometric strength": also called maximum static strength, and occurs when the athlete exercises a voluntary activation of maximum intensity against an insurmountable resistance. It corresponds to the "maximum force peak". Each value of "maximum isometric strength" must be accompanied by the angulation and position in which it has been achieved, since the results obtained vary.

- "Maximum eccentric strength": it is expressed in the situation in which the maximum neuromuscular activation capacity is opposed to a resistance that moves in the opposite direction to that which would move in the event of a concentric execution of the movement. It depends on the speed at which the eccentric activation occurs, so it must be taken into account. The "maximum eccentric strength" values are usually 150% of the "maximum isometric force".

- "Maximum dynamic strength": is the maximum expression of the concentric strength, and is normally when the resistance moves in the opposite direction to that of the gravity force. In practice, it expresses itself when the athlete is only able to perform a single repetition in that set. In this case, the "maximum dynamic strength" will refer to the exercise with which it has been measured and, with greater precision, to the angle at which the lowest resistance travel speed occurs.

- "Maximum relative dynamic strength": corresponds to the maximum strength expressed at resistances lower than that necessary for the "maximum dynamic strength" to be expressed, so that the subject may perform more than one repetition in the set. The "maximum relative dynamic strength" equals the maximum value of force that can be applied with each percentage of the "maximum dynamic strength". We can also define it as the neuromuscular capacity to print velocity at a lower resistance than that with which the "maximum dynamic strength" is expressed. This expression is fundamental as an objective of the training, since it is the main and most frequent strength expression in the competitive environment. The latter, referring to the one applied in the competition gesture, is called "specific maximum relative dynamic strength" (or useful or functional force).

-   "Explosive strength": corresponds to the relationship between the force produced and the time needed for its application. It is directly related to the "rate of force development" (RFD), and in turn to the capacity of the neuromuscular system to develop a high speed activation or to produce a strong acceleration in the strength expression. Within explosive strength, we find the following distinction (Tous Fajardo, 1999):

o   "Initial strength": concept that refers to the capacity to express a great force at the beginning of muscular activation and in a very short time. In a practical way, the force produced in the 30-50ms is considered as "initial strength". It takes place at the beginning of muscle contraction, and is very little modifiable with training.

o   "Acceleration strength": concept that refers to the muscular capacity to exert muscular tension as quickly as possible in a muscular action already started.

o   "Maximum explosive strength": the best relationship between force and time in the "f-t" curve. It is the maximum production of force per unit of time that a subject is able to apply.

-  "Elastic-explosive strength": to the "explosive strength" described above, is added the intervention of the elastic energy accumulated in the elastic components of the muscle-tendinous apparatus. During the stretching phase of a "stretching-shortening cycle", the motor actions involve a counter-movement, in which this elastic energy is used. For this energy to be used, the transition between the two phases of the "stretch-shortening cycle" must be above or below 200ms. A typical exercise for training and assessment of this expression is the counter-movement jump (CMJ).

- "Elastic-explosive-reactive strength": an increase in neuromuscular tension is added to the previous one, due to the incorporation of the myothatic reflex. However, we must emphasise that for this expression to occur, the stretching and transition phases of the "stretching-shortening cycle" must be very short and fast (above or below 100-150ms). The "drop jump" (DJ) would be an example of an exercise dependent on this force expression.

After this detailed analysis of strength expressions, it is necessary to introduce a new concept, called "rate of force development" (RFD). This concept could be defined as the relationship between the applied force and the time necessary for it, being able to calculate in the "f-t" curve. Moreover, this is decisive when referring to the expression of the existing force in each movement (Tous Fajardo, 1999), as well as in sports performance. It has been seen how two subjects (trained and untrained) can have a similar "maximum relative strength", but have a very different "rate of force development", being much higher in the trained subject (González Badillo & Gorastiaga Ayestarán, 1995). However, and without wishing to delve deeper into this moment, the "rate of force development " will be a subject that we will deal with later, since it was not the subject to deal with in this entry.

See you in the next post. 
May the force be with you!

References

Blázquez Sánchez, D. (1993). Fundamentos de educación física para enseñanza primaria. INDE.

González Badillo, J. J., & Gorastiaga Ayestarán, E. (1995). Fundamentos del entrenamiento de la fuerza : aplicación al alto rendimiento deportivo. INDE Publicaciones. Retrieved from https://www.inde.com/es/productos/detail/pro_id/194

González Badillo, J. J., & Ribas Serna, J. (2002). Bases de la programación del entrenamiento de fuerza. INDE. Retrieved from https://www.casadellibro.com/libro-bases-de-la-programacion-del-entrenamiento-de-fuerza/9788497290135/868694

Tous Fajardo, J. (1999). Nuevas tendencias en fuerza y musculación. J. Tous. Retrieved from https://www.casadellibro.com/libro-nuevas-tendencias-en-fuerza-y-musculacion/9788460599357/684911