Sustained versus repetitive standing trunk extension results in greater spinal growth

Key points

1. 01Sustained trunk extension (held for a set duration, repeated 5 times) produced roughly twice the spinal height gain compared to repetitive trunk extension in the first session.
2. 02The sustained group showed significantly greater reductions in most pain and current pain scores over two weeks.
3. 03Both groups improved in modified Oswestry scores, but neither reached the 6-point minimal clinically important difference, and there was no difference between groups.
4. 04Symptom centralization improved equally in both groups with no significant difference.
5. 05About 11% of recruited participants could not tolerate standing trunk extension and were excluded, indicating this approach is not suitable for all patients with low back pain.

How it was conducted

Design

Randomized clinical trial, pre-test post-test comparison group with 2-week follow-up

Participants

30 adults with musculoskeletal low back pain and directional preference toward extension, mean age 53.8 plus or minus 17.5 years, 18 women and 12 men

Groups

Repetitive trunk extension (RTE, 5 repetitions over seconds with 15-second rests) vs. sustained trunk extension (STE, held for set duration, 5 times with 15-second rests)

Primary outcome

Spinal height change measured by stadiometry after a standardized spinal loading protocol

Secondary outcomes

Pain (Numerical Pain Rating Scale), symptom centralization via body diagram overlay, and Modified Oswestry Low Back Pain Disability Questionnaire

Follow-up

Two sessions, approximately 2 weeks apart

What they found

• Session 1 spinal growth: RTE 2.07 plus or minus 1.32 mm vs. STE 4.54 plus or minus 1.61 mm (p < 0.001; effect size ES = 1.67).
• Session 2 spinal growth: RTE 2.39 plus or minus 1.46 mm vs. STE 3.91 plus or minus 2.06 mm (p = 0.027; ES = 0.85).
• Most pain reduction between sessions: STE from 5.4 plus or minus 1.6 to 2.6 vs. RTE from 2.4 to 1.9 (p = 0.0013; ES = 0.23).
• Current pain reduction: STE from 3.4 plus or minus 1.8 to 0.87 plus or minus 1.1 vs. RTE from 2.4 to 1.9 (p = 0.006; ES = 0.24; large effect).
• Modified Oswestry scores improved in both groups but with no significant difference between groups (p = 0.88); 7 of 30 participants (23%) reached the MCID of 12-point decrease.
• Centralization improved by a median of 1 point in both groups with no significant difference (p = 0.213; ES = 0.262).
• 57% (17 of 30) of participants reported greater than or equal to 2/10 pain improvement (MCID for pain).
• Home exercise compliance: RTE 91%, STE 87%.

Limitations

• Small sample (n = 30) with groups that differed at baseline on Modified Oswestry scores and had heterogeneous symptom chronicity, which may have influenced results.
• No long-term follow-up beyond 2 weeks, so durability of spinal height and pain improvements is unknown.
• Baseline current pain levels were relatively low, which may have limited the ability to detect pain differences.
• The RTE group had higher average age and greater symptom chronicity than the STE group, potentially confounding group comparisons.

Why it matters

For patients

People with low back pain who respond to extension-based movements may get more relief from holding a trunk extension posture (sustained) than from repeatedly moving in and out of it.

For clinicians

When prescribing McKenzie-style standing extension exercises, sustained holds appear to produce clinically larger spinal height gains and pain reduction than repetitive movements, though functional outcomes are equivalent.

For readers

This small RCT provides preliminary evidence for preferring sustained over repetitive standing trunk extension in extension-biased low back pain, but the short follow-up and small sample call for replication before strong clinical recommendations.