Background and Aim: Few studies have assessed the reliability of postural balance measures during dynamic balance performance that introduce additional challenging to postural control system. In addition sometimes in the static conditions some deficiencies of the postural control system may not be revealed obviously therefore the aim of this study was to assess the reliability of postural control parameters during functional performance on force plate in healthy subjects.
Materials and Methods:  Ten healthy male subjects (mean age: 25.4 years, weight: 68.2 kg height:176.9cm) participated  in this study. None of the subjects were involved in sport activities. Every subject performed three 15seconds trials of eyes open single leg stance on a force plate during dynamic balance task. Participants grasped object with hand at their waist level and release it at above shoulder level.  The reproducibility of the center of pressure (COP) deviations (average speed &length of path) was assessed. All participants were tested on 2 sessions with an inter-measurement interval of 7 days. COP data was collected for each trial. The intraclass correlation coefficient (ICC) was used as parameter of intra-session and inter-session (Test-Retest) reliability.
Results: The ICCs for intra-session reliability of average speed and length of COP path were  0.89 and 0.91  respectively. The ICCs for inter-session reliability were 0.95 and 0.96 respectively.
Conclusion: The study showed high and very high reliability for center of pressure measures during dynamic balance task. Therefore this dynamic performance can be used as a balance pattern in postural control assessment. These can be used as reliable parameters in dynamic postural control assessment due to high reliability of average speed and length of COP path

Background and Aim: The calculated parameters of the center of pressure (COP) are suitable indicators for evaluating balance in patients after rehabilitation. Therefore, determining the reliability level of each parameter is a matter of great importance. This study tried to determine the reliability of some parameters of the COP sway in patients with myofascial neck pain in different postural situations.

Materials and Methods: The present study is a test-retest reliability design. Twenty patients with myofascial neck pain performed a single and a double leg test with open and closed eyes on a force plate and with open eyes on foam in three sessions with a 30 minute intervals for 30 seconds. Antero-posterior and medio-lateral sway range, mean velocity and mean area of sway were calculated.

Results: The mean velocity showed high reliability (0.98) in all situations, but the other parameters were variable in different situations.

Conclusions: The results showed that some COP parameters are highly reliable in assessment of patients with myofascial neck pain.

Keywords: Reliability, Myofascial neck pain, Center of pressure, Force plate

Background and Aim: Fractal dimension (FD) as a measure of system complexity and a chaos and nonlinear dynamics tool has appeared successful in distinguishing subjects with different specifications such as proficiency level. The purpose of this research was to evaluate the capability of FD analysis of postural stability in distinguishing elite Wushu sportsman for dispatching to various competitions.

Materials and Methods: Eight elite and eight non-elite Wushu sportsmen from Talou section participated in this research and performed a difficult balance motion called “backward balance”. Center of pressure (COP) traces were recorded and Higuchi algorithm has been used to obtain fractal dimension of COP displacement time series. Average of FD of two groups were compared with an unpaired t-test.

Results: In both directions of anterio-posterior (AP) and medio-lateral (ML), average values of FD in elite group were significantly more than non-elite group (p<0.05). Subsequently, implementing a receiver operating characteristic (ROC) analysis indicated that FD analysis method performance is very good in AP direction (Area under the curve or AUC=0.938) and good enough in ML direction (AUC=0.668).

Conclusions: Postural control system acts more complex in elite group because of their more proficiency. FD analysis of COP time series could help coaches in choosing elite Wushu sportsman even among a group of skilled Wushu sportsmen. 

Keywords: Wushu, Postural stability, Fractal dimension, Receiver operating characteristic (ROC), Center of pressure (COP)