Abstract

Background and Aim: The Action Observation stimulates mirror neurons. It is the effective acquisition of skills, motor learning and memory formation and this feature can be used to treat injuries such as stroke. The aim of this study was to investigate the effect of action observation on the symmetry of weight distribution in lower limbs and stability indices in semi-dynamic stability.

Materials and Methods: This study was conducted in 91 healthy male and female non-athletes aged 20 to 45 years. Data were collected through questionnaires and clinical examinations. Subjects were randomly assigned to men and women with and without film observation. A 3-minute short film was preapared to stimulate mirror neurons in the standing position on the symmetry weight measurement system and Biodex platform system. In film observation group, before and after viewing the film, distribution of weigh bearing on the right and left sides, and dynamic stability indices in two stability levels of 5 and 8 were measured and calculated indices of total, anterior - posterior and medio- lateral indices were obtained. In without film observation group, measurements were performed at the similar time as a film observation group.

Results: Percentage weight distribution showed no significant difference between the two groups. The comparison of percentage changes between two groups showed that observation of the film improved significantly total index (p <0.002) and anterior – posterior index (p <0.018) in the stability level of 5. Analysis of the results in the separately men and women groups, showed the significant improvement of these parameters only in women group after film observation regardless of film observation, the percentage changes of stability indices showed no significant differences in men groups.

Conclusion: Action Observation (by activating the mirror neurons) can be effective methods to improve the balance standing of healthy people on the stable and unstable surfaces. Significant improvement stability indices in women after viewing the film, may suggest the greater sensitivity of women's mirror neurons related to men.

Keywords: Mirror Neurons, Action Observation, Symmetry of Weight Distribution, Dynamic Stability, Stability

Background and Aim: The normal response of H-reflex depression (HD) was reduced in chronic spinal cord injury (SCI) patients. The reduction of this normal response can lead to increase the muscle tone and spasticity. The purpose of this study is to investigate the effect of tripolar cathodal stimulation on HD in SCI patients.

Materials and Methods: This study was conducted in 10 volunteered SCI patients and 13 healthy male and female aged 28.91 ± 5.78 years. H-reflexes were elicited at 0.2, 5 and 0.2 Hz and intensity of 65-70 percent of the maximum H-reflex amplitude, before and after tripolar cathodal electrical stimulation of the spinal cord at T₁₁ level.

Results : Before trioplar stimulation, H-reflex amplitude decreased with increasing stimulation frequency only in healthy group. H-reflex amplitude decreased from 2.60 ± 1.48 to 1.34 ± 1.30 by 5Hz frequency (P=0.000). After trioplar stimulation in SCI patients group, HD increased with increasing stimulation frequency and H-reflex amplitude decreased significantly from 2.21 ± 1.98 by 0.2 Hz frequency to 1.29 ± 1.50 by 5Hz frequency(P=0.014).

Conclusion: Application of one session of cathodal trioplar stimulation can result the returning of normal HD in SCI patients. Cathodal trioplar stimulation is a non-invasive, without side effects, and an inexpensive method that may be a valuable tool to return the normal inhibition and modulating behavior of the spinal cord circuits.

Keywords: Spinal cord injury , Tripolar stimulation, H-reflex depression, Soleus muscle

Background and Aim: Despite the widespread use of whole body vibration (WBV),especiallyin recent years, its neurophysiological mechanism is still unclear and the results about the facilitatory or inhibitory effects of WBV widely vary in different studies. The aim of this study was to compare between immediate (one session) and short term (12 sessions) effects of WBV on the spinal motor neurons excitability in healthy young men.

Materials and Methods: Ten voluntary non-athlete healthy young-men (mean age:26.1±2.23) were participated in this study.In the sham sessions subjects stood on the turned off vibration plate while were maintaining the semi-squat position and then after 2 weeks wash-out, vibration training sessions were done on the same position with frequency of 30 HZ and peak to peak amplitude of 3 mm training sessions (sham & vibration) consisted of 12 sessions (3 sessions per week) and 4 set in each of them, weekly one set added to the training protocol. H reflex recruitment curve of soleus muscle was recorded before and after first and also 12th sessions in both sham and vibration training protocol. Ascending slope of recruitment curve, threshold and peak amplitudes and related intensities, amplitude of Mh and Hmax/Mmax ratio were determined.

Results: Immediate effects of vibration training 12th session caused a significant decrease of threshold amplitude and an increase of peak intensity (p=0.05 and p=0.05 respectively). Short term WBV training significantly decreased the threshold intensity of soleus recruitment curve (p=0.01).

Conclusion: The results suggest the inhibitory effect of acute WBV training on the spinal motor neurons excitability. It seems that short term WBV training may be effective to facilitate the motor neurons excitability or increase the muscle spindle sensitivity.

Key Words: Whole body vibration, H reflex recruitment curve, Soleus muscle, Short term training