In the field of sports training and recovery, the work of muscular strength has become the star theme in terms of its influence on the performance of athletes. In fact, in relation to the training of the inferior members, the scientific evidence indicates that, to increase the other two physical qualities conditioned (speed and resistance), it is necessary to work and to increase the muscular strength.

Randomized intervention trial with sample size of 80 subjects divided into 4 groups (n = 20) of muscular work: concentric, eccentric, concentric-eccentric and isometric. Ages between 21-23 years.

For all the above, the investigators will study as a main objective analyze what type of muscular work is most effective in order to improve some variables of the performance of explosive muscular strength, and to try to determine if that improvement is due, exclusively to the developed training or to the genetics of the subjects and compare the results obtained in the variables of vertical jump, power of saint, horizontal jump and speed 60 meters, before and after the execution of each one of the muscular works dynamic among themselves, and compared to the muscular work isometric.

In the field of sports training and recovery, the work of muscular strength has become the star theme in terms of its influence on the performance of athletes. In fact, in relation to the training of the inferior members, the scientific evidence indicates that, to increase the other two physical qualities conditioned (speed and resistance), it is necessary to work and to increase the muscular strength.

To this end, numerous training methods have been developed, in which research and technology provide new solutions that favor and enhance the muscular work done.

Therefore, in the performance of an athlete this work of force influences, and what this implies: type of muscular contraction, way of working that contraction, recruitment of the muscular fiber, and modality of muscular strength developed. But, this performance, it appears that it can also be influenced by environmental parameters such as diet, technological support and genetic factors. It has been discovered in the human genome 12 million of polymorphisms, but it is only recorded that some 214 may have influence on physical qualities, and all of them, the most studied in terms of their influence on sports performance are: genes Muscular, and more specifically the ACTN3, and vasomotor genes that affect the production of energy and that intervene in metabolic processes (ACE gene).

• Design: Randomized intervention clinical trial, double blinded.
• Sample: by contrast of hypothesis, a sample size of 80 subjects divided into 4 groups (n = 20) of muscular work: concentric, eccentric, concentric-eccentric and isometric. They were randomized using excel software. As criteria of inclusion, subjects that did not present musculoskeletal lesions in the lower train at the time of the study, which showed a serious commitment to perform the entire muscle training, which were not subject to another type of plan Training that could interfere with the results obtained from the measurement of the study variables, and that would not have been diagnosed with hypertension.
• Methodology:

The duration of the muscular work was 12 consecutive days, measuring before and after the same variables indicated below.

The protocol of work was as follows: 4 series of 12 repetitions of the type of muscular contraction of each group, with one minute of rest between series and series. For the muscular work isometric: 6 seconds of contraction, with 20 seconds of rest, for a total working time of 12 minutes.

As a material for muscular work, the muscle brace or Russian belt was used for the three types of dynamic muscular work and the quadriceps bench for isometric muscular work. Other variables that were taken into account were: sex, age, weight, height, body mass index, blood pressure and heart rate.

As explosive force variables were measured: The Jump Power (Sayers formula), the vertical jump (the Sargent jump test), horizontal jump and speed 60 meters.

Other variables that were taken into account were: sex, age, weight, height, body mass index, blood pressure and heart rate.

At the end of the 12 days of training was extracted 10 ml of blood to each subject of the sample, then obtain the DNA analysis of the genotypes of the two genes analyzed.

Inclusion Criteria:

• Subjects that did not present musculoskeletal lesions in the lower train at the time of the study.
• Subjects that showed a serious commitment to perform the entire muscle training.
• Subjects not subject to another type of training plan that could interfere with the results obtained from the measurement of the study variables.

Exclusion Criteria:

• Subjects with high blood pressure.

The participant was blinded not knowing the treatment to which he was submitted and outcome assessor responsible for collecting the results, without commenting on the group from which the patient came. Only the principal investigator knew the group to which the patient belonged.