The improvement in cervical ROM in MET group after the post intervention can occur due reflex relaxation, viscoelastic changes and stretch tolerance. Reflex muscle relaxation can be demonstrated on the basis of Golgi tendon organ activation and inhibition of alpha motor neuron. 42 Combination of isometric contraction and stretching is applied in MET and that might be more effective to produce viscoelastic changes in shorten muscle than passive stretching because greater force could produce more viscoelastic changes in the muscle which can leads to increase the length of the shorten muscle.
The rationale behind the increase in ROM after application of Muscle energy technique is due to reduction in reflex activity. It modifies the stretch perception according to the nociceptive nerve ending in the muscle and joint and they play most important role via pain gate control or neurotransmitter modulation. Repetitive isometric muscle contraction increase blood flow, lymphatic fluid drainage and remove the paraspinal congestion.43 according to J.B. Feland,Maximal voluntary muscle contractions can produce delayed onset muscle soreness and may increase the risk of injury and also cause fatigue due to muscle contraction. Static holding during muscle contraction caused compression of capillaries during the muscle contraction which supplies oxygen to the blood and remove the wastage products 44.
Results of the present study for MET group for improvement in cervical ROM were similar to previous studies which were conducted over neck area 45 and other muscle and joint. Classidy et al 46 demonstrated in their study that immediate increase in cervical ROM in mechanical neck pain patients who were treated with the MET. Schenk et al 47 concluded that MET group shown more improvement in cervical ROM. Denise et al 48 concluded that MET produced a significant improvement in cervical ROM.