Thus far, we have presented certain mechanisms and principles, indicating the possibilities and conditions that must be met in order to develop muscle strength. Since the general physiological mechanisms differentiating the options of developing strength have already been outlined, we can now proceed with discussing the specific modes of action that are knowingly and consistently applied in the daily work on this characteristic. We call these the methods of building muscle strength.

For a better understanding and easier learning of these methods, certain terms that will be used on more than on occasion should first be explained in as accessible a way as possible. And thus, muscles can work in different ways:

The values of strength displayed by the above differ as does the degree of fibres involvement in each type of muscle activity.
Very informative and also fundamental to the understanding of muscle action modes are the results of studies on an isolated frog muscle, conducted by A. V. Hill more than half a century ago. The most important conclusions for the purposes of this publication are presented on the schematic diagrams drawn up based on the experiments carried out by several authors – and these are fundamental to the understanding of the essence of muscle strength building process. An analysis of the diagram shown in Figure 3 provides a number of valuable conclusions as regards the methods of building muscle strength. The first one is that the more the movement speed increases, the less muscle strength is involved and, conversely, the lower the value of the speed the greater involvement of muscle strength. It should also be noted that in very slow movements of concentric nature, where V-> 0 (V approaches 0) the strength involvement is the highest. Thus, if we want to develop our musculature through a full muscle involvement, in practice we cannot achieve it through fast, dynamic movement but rather should by deliberately slowing them down.

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Fig. 3. Relationships between the strength and speed, as well as power and speed during the shortening (concentric conditions) and muscle stretching (eccentric conditions.)
Schematic diagram developed by Z. and L. Trzaskoma and A. Gajewski

Further analysis of the diagram leads us to the origin of X and Y axes, at which there is no movement as the speed stands at zero. This is the isometric mode of muscle action. It is obvious that in isometric conditions the muscle strength involvement is greater than that in concentric movements. Therefore, a conclusion should be drawn – one that is not very popular in the sports community – that tensing the muscles without changing their length is more effective in the development of their strength than concentric movements (probably most often used in training). Armed with this knowledge, we will no longer be surprised watching the drenched in sweat and almost fainting from the effort bodybuilders while they present the compulsory poses and other static positions during (isometric!) competitions. When analysing further Figure 3, we notice – when moving to the Y axis – a further increase in strength involvement. This part of the graph shows the eccentric muscle activity, i.e. one in which the attachments move away from each other. This suggests that the most effective work in building muscle strength are the eccentric exercises, which actually proves true under certain conditions. In summary, the graph plotting the strength against the speed of movement enables the observation that the muscle exhibits the greatest strength when acting in an eccentric system, while the smallest – in the concentric one. In the case of isometric tension, the efficiency of such activity for muscle strength building is also higher that that during concentric movements.
At this point, please compare the amount of work done during training using the concentric movements with that in other movement regimes. What conclusions can be drawn? I suspect that they are common to all of us… Some things needs to be changed in the workout in order to increase the involvement of strength and, consequently, to improve the muscle strength, isn’t that so?