The Influence of the Sacroiliac Joint Manipulation on Changes in the Values of the Center of Pressure in the Process of Maintaining Static Body Balance

The aim of the project was to determine the effectiveness of HVLA manipulation in maintaining static body balance. To implement it, it was necessary to conduct an experiment consisting in performing HVLA manipulation in people with SIJs hypomobility and checking whether it affects the COP parameters. It was assumed to measure these parameters twice (before (PRE) and after (POST) manipulation) and compare them with the measurements in the C group (sham manipulation).

The sample size necessary to power the study was determined at the test planning stage, using the G * Power 3.1.9 software. The standard threshold α = .05 was established; then the acceptable power level of the 1-β = .90 test and the expected moderate effect size η2 = .30 were determined for within-between interaction. The calculated total expected size of the sample is N = 32, i.e. 16 subjects in one research group, assuming that their number will not decrease during the study. With a higher test power 1-β = .95 and a moderate achieved result for observed effect size η2 = .25, the sample should have to consist of 26 subjects per subgroup. It was decided to examine a slightly larger number of available entities due to the possibility of excluding incorrect data.

Poznan University of Physical Education's students were invited to the research, electronically. Before starting the research, they were informed about the purpose and manner of conducting the research, and the type of methods used. Participation in the experiment was voluntary and free. Participants could withdraw from cooperation in the research at any time. They obtained assurance that the data obtained will be used only for scientific purposes and their processing will be fully anonymous.

Among 202 students of the Poznań University of Physical Education who responded to the invitation to the study project interview has been conducted, as a result of which 22 people were excluded from further actions due to disqualification criteria. Then sacroiliac mobility tests has been performed which made it possible to recognize hypomobility in 72 people. From the group of people with hypomobility, 36 people were randomly selected and included in the E group. From among people without hypomobility, 31 people were randomly selected for the C group. An random number table was used in the draw. The subjects did not know any group they were assigned to.

Subsequently, the examination of each project participant consisted of performing podometric measurements and SIJs mobilization in the E group or placebo in the C group, and re-performing functional tests and podometrics in both groups after the procedure. At the stage of analyzing data rejected 8 people who did not meet the assumed criteria, thus finally there were 30 people in the experimental group and 29 in the control group.