Effects of Ascending and Descending Direct Current on Grip Strength. Evaluation Through Dynamometry and Myofeedback. Randomized, Controlled Trial.

1. Methodology

This research has the characteristics of a random analytical experimental design (ECA). The study was conducted in the laboratory of physiotherapy, room 401, 4th floor, building C5 University Andres Bello (UNAB), Faculty of Rehabilitation Sciences, Campus Casona, Nº700 Street Fernández Concha, Santiago, Chile. The sample was selected from the university population that is part of the faculty. The study was submitted to the ethics committee of the East Metropolitan Health Service (SSMO) of Salvador Hospital. Once approved by the ethics committee began the investigation. It was taken as population all students of the Faculty of Rehabilitation Sciences, made up of races Physical Therapy, Speech Therapy and Occupational Therapy. The study group was determined through a simple random sampling process, which was conducted through a questionnaire with closed questions. This questionnaire allowed select participants according to the inclusion and exclusion criteria proposed in the work. The number of participants was taken for the convenience of researchers. The final sample included 150 participants. Student population share similar characteristics, so that most made them compatible for the sample. Inclusion criteria were established: participants aged 18 years and people that they should not discomfort or pain on the handgrip. Moreover Exclusion criteria were considered: muscle pathologies skeletal hand, wrist or elbow in the last 6 months, the presence of materials osteosynthesis or endoprosthesis in areas of application, peripheral neurological diseases such as neuropraxias or nervous cuts, skin disorders application areas, such as burns, wounds, scars, apprehension or fear of the application of electrotherapy, non-completion of the evaluation protocol / intervention designed for studio or away from it, and do not sign the consent for participation.

3 stages of conducting the study were designated. Stage 1 called "The Sample Phase", had a duration of one week. This Phase consisted of the implementation of the survey to students, followed by analysis of the collected information and registration for a first filter potential participants. The survey was applied to all courses of the Faculty of Rehabilitation Sciences. The first filter was given with the survey questions that has specifics questions with the inclusion and exclusion criteria. Participants who met the characteristics of participation and were invited to join the study. The students will be contacted personally. Students interested will be explained in detail the study and were asked to give their written consent. Informed consent reflected the 4 principles of bioethics so as to safeguard the integrity of each person.

The second stage of design called "Evaluation Phase" lasted 5 days. In this phase the ability to perform hand grip on the participants according to the protocol established in the investigation was assessed. The strength assessment will be probe in the same conditions in which they worked on the study. At this level, people explained everything concerning the characteristics of electrical stimulation used, and as applicable. This stage marked a second filter instance dismissing students who had discomfort or inability to perform the handgrip. After this phase had the final number of participants who made up the final sample of the study, giving way to step 3.

The stage called "Experimentation Phase" had a duration of 3 weeks. The sample was randomly so as to establish three working groups, a group called "Cathode Stimulation", another group called "Anode Stimulation" and a third group called "Control Group". The group "Cathode stimulation" includes 48 participants, while the "Anode Group" had 52 participants and the "Group Control" 50 participants.