Comparison between the different muscles in each stage of the four-point kneeling exercise showed that muscle activation was significantly different in all the exercises (P<0.001). The post-hoc test with Bonferroni correction revealed that in each exercise, the right

TrA had the highest activation of all the muscles, whereas right and left multifidus muscles exhibited the lowest activation pattern (table 1). Table 1 Comparison of mean muscle activation between the different levels of the four-point kneeling exercise According Inhibitors,research,lifescience,medical to the results, statistically significant differences (P<0.05) were found in the activation of all the muscles, except for

the right IO. On the other hand, the amplitudes of these muscles for the bird-dog position Inhibitors,research,lifescience,medical were significantly higher than those recorded for right arm extension. Furthermore, a statistically significant difference was found between left leg extension and bird-dog position (P<0.05) in as much as the left multifidus was activated at a significantly higher level than the other muscles in the bird-dog stage. Discussion The current study aimed to compare the EMG amplitudes of trunk and lumbar muscles during the performance of the three stages of the four-point kneeling position. The results showed that the mean activation of abdominal and lumbar Inhibitors,research,lifescience,medical muscles was different in the three stages of the four-point kneeling exercise. Overall, the right TrA had the highest activation of all the muscles, while right and left multifidus muscles showed the lowest activation pattern. This finding is related to the

role of the TrA in every Inhibitors,research,lifescience,medical trunk and limb movement. In order to provide spinal stability, the central nervous system (CNS) estimates the amount of disturbance produced by the motion of the limbs and sends the inputs to the TrA proprioceptive receptors, which trigger coordinated Inhibitors,research,lifescience,medical muscle activation. Therefore, the see more feed-forward mechanism is performed by the CNS in two ways: GPX6 (1) non-directional for the excitation of intrinsic muscles and (2) direction-specific for the control of spinal situations.4 The TrA is a primary trunk stabilizer via the modulation of intra-abdominal pressure, tension through the thoracolumbar fascia, and compression of sacroiliac joints. Richardson et al.4 demonstrated that a voluntary contraction of the TrA reduced the laxity of the sacroiliac joint. Another study showed different levels of the feed-forward contraction of the TrA during rapid arm movements.22 The findings of the present study revealed that the activation of left IO and right and left mulitifudus muscles in the bird-dog position was higher than that in the other two exercises.