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Background and Aim: Multifidus muscle is one of the short and deep posterior Paraspinal muscles, which gives stability to the spine during various activities. Studies have shown that in people with neck pain, weakness and atrophy of neck muscles are major factors in the incidence of neck pain. Measurement of muscle's dimensions by ultrasonography provides an opportunity to be able to objectively assess muscle atrophy or hypertrophy. This study aimed to assess symmetry of cervical multifidus muscle size in females with chronic non-specific neck pain and healthy by ultrasonography apparatus.

Materials & Methods: Twenty five women with unilateral chronic nonspecific neck pain and 25 healthy women were participated in this study. All subjects were employed and more than 4 hours working with computers or paying office in a day. Imaging of the cervical multifidus muscles were done bilaterally in the level of the fourth vertebra. Anterior-Posterior Dimension(APD), Lateral Dimension(LD), Cross-Sectional Area (multiplied of two diameters(APD&LD)) and the Shape ratio (Lateral diameter divided by the Anterior-Posterior diameter(LD/APD)) of the muscle were measured and recorded. 

Results: Multifidus muscle size in patients group was smaller than the healthy group. In patients group, size of multifidus muscle in the painful side was smaller than the opposite side. Asymmetry of muscle size between the two sides, in the patient group was higher than the control group (P < 0.05). The ratio of smaller size to the larger size of the muscle, in the healthy group was higher than the ratio in the patient group (P < 0.05).

Conclusion: In patients group, asymmetry of the muscle size between two sides, also smaller size of the muscle in the painful side, showed that muscle atrophy has happened in the involved side.

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Background and Aim: Whole body vibration (WBV) is a new therapeutic modality which improves muscle function, proprioception and postural control by creating an oscillatory mechanical stimulation. The aim of this research was to investigate the immediate effect of WBV on postural control in young adults.

Materials and Methods: In this quasi-experimental study, 22 healthy subjects were participated as a single group. Non-probability simple sampling method was used. Subjects were treated with 4 minutes WBV bout. The subjects repeated four times a 60-s light exercise program according to instructions which was shown by the therapist. During the vibration intervention, the vibration frequency increased in 1 minute intervals from 15 Hz for the first minute to 30 Hz for the last minute. Postural control indexes were recorded using the Biodex Balance system in situations of two leg standing with open and close eyes that included overall stability index (OSI), anterior-posterior stability index (APSI), medial-lateral stability index (MLSI) . In order to analyze the data, paired t-test was used.

Results: The results indicated that in the case of standing on two legs with eyes open, OSI and MLSI were statistically significant (P = 0.02; P = 0.01, respectively) and with eyes closed, OSI, APSI and MLSI were statistically significant (P = 0.000; P = 0.001; P = 0. 001, respectively).

Conclusion: Four minutes WBV bout can induce improvement of postural control and balance in young adults.

Keywords: Whole body vibration, Balance, Young adults, Stability