McKenzie Extension Protocol Versus Core Stability Exercises Combined With Spinal Decompression in Discogenic Lumbar Radiculopathy

Background and Rationale

Low back pain (LBP) ranks among the most prevalent musculoskeletal conditions globally. Point prevalence estimates are roughly 9-12% worldwide, with up to 23% of adults reporting an episode within a one-month period. Lifetime prevalence estimates range as high as 40-80%. Global burden data from 2021 indicate that approximately 453 million working-age adults were affected by LBP. Within this broad population, discogenic low back pain (DLBP) constitutes a distinct subgroup in which pain originates from structural and biochemical changes within the intervertebral disc itself, most often disc degeneration, rather than from nerve root compression or other spinal pathology. Depending on the diagnostic method employed, discogenic pain accounts for approximately 22-50% of chronic low back pain cases. A further subset of these patients develops lumbar radiculopathy, wherein nerve root irritation produces radiating leg pain. Population data suggest that roughly 12% of adults with back pain exhibit clinical radiculopathy, though substantial variation in reported incidence exists depending on the population studied.

Non-surgical spinal decompression is a motorized, computer-controlled traction therapy that applies gentle, feedback-regulated distraction forces to the lumbar spine. It is theorized to reduce intradiscal pressure, transiently increase disc height and foraminal space, and enhance fluid and nutrient exchange within the disc, thereby supporting disc hydration and reducing mechanical loading on degenerated segments. Several recent studies report improvements in pain and disability following non-surgical decompression, particularly when it is combined with conventional physical therapy rather than used in isolation.

Two of the most established adjunct exercise approaches utilized alongside decompression are the McKenzie Method, also known as Mechanical Diagnosis and Therapy (MDT), and Core Stability Exercises. The McKenzie approach is a structured system of repeated movements and sustained positions used to classify patients into mechanical subgroups and guide treatment based on their directional preference. A central therapeutic phenomenon in this approach is centralization, in which distally referred pain progressively retreats toward the spinal midline in response to specific repeated movements, a pattern associated with favorable prognosis. Core stability exercises, by contrast, focus on activating and coordinating the deep trunk musculature, including the transversus abdominis and lumbar multifidus, to improve co-contraction, segmental control, and postural stability, thereby reducing nociceptive input from unstable or overloaded spinal structures.

Existing comparative literature remains mixed. Some studies report that core stabilization produces greater reductions in pain and disability than McKenzie exercises in patients with lumbar radiculopathy, while other trials, including a one-year follow-up RCT among patients with a McKenzie directional preference, found no clear superiority of either approach when compared to motor control or core stability exercises. Evidence specific to discogenic radiculopathy managed with decompression is even more limited. One RCT found that adding spinal decompression to core stabilization produced larger within-group improvements than core stabilization alone, yet no identified trial has directly compared McKenzie-based and core-stability-based exercise protocols when both are paired with decompression therapy in this specific population.

Problem Statement

Given that spinal decompression is widely used as a conservative treatment for lumbar disc pathology, and current guidelines do not specify which adjunct exercise approach, McKenzie or core stability, produces superior outcomes when combined with decompression, clinicians lack clear direction when selecting rehabilitation strategies for discogenic low back pain with radiculopathy. This trial is designed to address that evidence gap directly.

Study Design and Methods

This is a single-blind, two-arm randomized controlled trial to be conducted at the Max Spine Rehab Center, Max Health Hospital. Eligible participants are adults aged 25-45 years with an MRI-confirmed posterolateral disc bulge, an NPRS pain intensity greater than 3 with radicular symptoms, and a positive Straight Leg Raise test. Individuals with a history of spinal surgery or significant trauma, increased kyphosis, active infection, pregnancy, scoliosis, systemic inflammatory disease, or cognitive impairment affecting participation will be excluded. A total of 42 participants, calculated using OpenEpi, will be recruited via purposive sampling and randomized by lottery method into two groups of 21.

Both groups will receive identical spinal decompression therapy, consisting of supine mechanical traction at 25-50% bodyweight force for 10-15 minutes in an intermittent 60-second hold and 30-second release cycle, immediately followed by their assigned exercise protocol. Group A will perform McKenzie-based extension exercises, including prone lying in extension, prone press-ups, standing lumbar extension, and repeated end-range extension guided by directional preference and centralization. Group B will perform core stability exercises, including the abdominal drawing-in maneuver, bridging, bird-dog, and side-plank or modified side support. Both groups will also receive standardized moist heat and interferential current therapy before exercise. Sessions will occur three times weekly for four weeks, totaling 12 sessions, with exercise dosage progressed according to individual tolerance and symptom response.

Outcome Measures

Four outcome domains will be assessed at baseline and post-intervention by a blinded assessor. These include pain intensity via the Numeric Pain Rating Scale (NPRS, 0-10), functional disability via the Oswestry Disability Index (ODI, 0-100%), lumbar range of motion in flexion, extension, and lateral bending via inclinometer, and lower-limb neural mobility via the Straight Leg Raise test angle. All instruments possess established reliability and validity for use in lumbar spine populations.

Data Analysis and Ethics

Data will be analyzed using SPSS to compare within-group and between-group changes across the two treatment arms. The trial will be conducted under Institutional Review Board approval. Written informed consent will be obtained from all participants, and provisions for voluntary participation, the right to withdraw at any time, and the receipt of active therapeutic intervention in both study groups will be ensured throughout.

Inclusion criteria

• Adults aged 25-45 years (both males and females)
• MRI-confirmed posterolateral disc bulge
• Pain intensity greater than 3 on the Numeric Pain Rating Scale (NPRS) with radiculopathy
• Positive Straight Leg Raise (SLR) test

Exclusion criteria

• History of spinal surgery or significant spinal trauma
• Increased kyphosis or active infectious disease
• Pregnancy, scoliosis, or systemic inflammatory conditions
• Cognitive impairments that may interfere with participation or assessment