The effect of repeated flexion-based exercises versus extension-based exercises on the clinical outcomes of patients with lumbar disk herniation surgery: a randomized clinical trial

Key points

1. 01Extension-based McKenzie exercises reduced disability (ODI) more than flexion-based or control (final ODI: McKenzie 21.72, Williams 17.71, Control 24.33; P < 0.001)
2. 02McKenzie group showed the greatest VAS pain reduction (final VAS 1.89 vs. Williams 1.71 vs. Control 2.46; P = 0.002)
3. 03Williams exercises produced superior trunk flexion endurance gains (final TFET 49.07 vs. McKenzie 41.34 vs. Control 35.76; P < 0.001)
4. 04McKenzie exercises produced superior trunk extension endurance gains (final mBST 45.93 vs. Williams 41.35 vs. Control 34.66; P < 0.001)
5. 05Return to work at 14 weeks did not differ significantly between groups (P = 0.06)

How it was conducted

Design

Single-blind randomized clinical trial (RCT), conducted in 2019 at Kermanshah University of Medical Sciences, Iran

Participants

90 adults aged 20-50 who underwent single-level lumbar laminectomy and discectomy

Groups

Williams flexion exercises (n=30), McKenzie extension exercises (n=30), control conventional rehabilitation (n=30); 87 completed the study

Intervention timing

Exercise programs started at end of week 6 post-surgery, continued 8 weeks (3 sessions/week, 45 min each); home-based, unsupervised

Primary outcome

Oswestry Disability Index (ODI) at end of week 14 post-surgery

Secondary outcomes

VAS pain, modified Biering-Sorensen test (mBST) for back extensor endurance, Trunk Flexion Endurance Test (TFET), and return to work

What they found

• ODI decreased in all groups (P < 0.001): Williams 29.85 to 17.71, McKenzie 31.17 to 21.72, Control 29.36 to 24.33; McKenzie reduced ODI significantly more than Williams (mean difference -4.00, P < 0.001) and control (mean difference -2.60, P = 0.019)
• VAS pain decreased in all groups: Williams 4.03 to 1.71, McKenzie 4.13 to 1.89, Control 3.93 to 2.46; McKenzie group showed greatest reduction (P < 0.001 vs. control; Kruskal-Wallis K2 = 12.11, P = 0.002)
• Trunk flexion endurance (TFET) increased in all groups: Williams 31.60 to 49.07, McKenzie 30.65 to 41.34, Control 30.03 to 35.76; Williams significantly higher than McKenzie (Z = -2.84, P = 0.004) and control (Z = -5.261, P < 0.001)
• Trunk extension endurance (mBST) increased in all groups: Williams 29.92 to 41.35, McKenzie 28.24 to 45.93, Control 28.93 to 34.66; McKenzie significantly higher than Williams (Z = -2.21, P = 0.027) and control (Z = -5.079, P < 0.001)
• Return to work at 14 weeks: yes in 63.2% overall; no significant difference between groups (K2 = 5.61, P = 0.06)
• 3 participants lost to follow-up (2 Williams, 1 McKenzie); final analysis on 87 subjects

Limitations

• Home exercises were not directly supervised; compliance was monitored only through biweekly outpatient visits and self-report
• No long-term follow-up beyond 14 weeks post-surgery, so durability of benefits is unknown
• Bio-behavioral factors (psychological status, fear-avoidance) were not measured and may have influenced outcomes
• Relatively small sample per group (n approximately 29 per group at completion) limits statistical power for detecting smaller differences

Why it matters

For patients

Patients recovering from lumbar disc surgery can benefit from starting a structured home exercise program at 6 weeks; either type reduces pain and disability, but McKenzie extension exercises may offer a faster functional recovery.

For clinicians

McKenzie extension exercises produced statistically greater improvements in ODI and pain compared to Williams flexion exercises after discectomy, making them a preferable first-line postoperative home program, though Williams exercises better target trunk flexor endurance.

For readers

This RCT provides direct head-to-head evidence comparing two widely used exercise protocols after lumbar discectomy, addressing a gap in post-surgical rehabilitation guidance.