McKenzie Neck Exercise Versus Cranio-Cervical Flexion Exercise on Strength and Endurance of Deep Neck Flexor Muscles, Pain, Disability, and Craniovertebral Angle in Individuals with Chronic Neck Pain: a Randomized Clinical Trial.

Purpose: To compare the effectiveness of McKenzie neck exercise and cranio-cervical flexion (CCF) exercise on strength and endurance of deep neck flexor (DNF) muscles, pain, disability, and craniovertebral angle (CVA) in individuals with chronic neck pain. Methods: Forty individuals with chronic neck pain were randomly allocated to the McKenzie neck or CCF exercise group. Each group performed exercises at home daily. The strength and endurance of DNF muscles were measured at baseline, immediately after the first exercise session, and each week follow-up for six weeks. Average pain over the past week was measured at baseline and each week follow-up for six weeks. Disability and CVA were measured at baseline and the end of six weeks. Results: At six weeks, both groups exhibited significant improvements across all outcome variables (p < 0.001) but there were no differences between groups (p > 0.05). The significant difference from baseline in the strength of DNF muscles was observed as early as the second week of each intervention (p <= 0.001). The significant difference from baseline in the endurance of DNF muscles was observed as early as the first week in the CCF exercise group (p < 0.05) and the second week in the McKenzie neck exercise group (p < 0.05). A significant decrease in pain intensity from baseline was observed after the first week in the McKenzie neck exercise group (p < 0.001) while it was after the second week in the CCF exercise group (p < 0.05). Conclusion: Both the McKenzie neck exercise and CCF exercise produced similar effects in enhancing the strength and endurance of the DNF muscles, decreasing pain, alleviating neck disability, and improving the CVA.