The core of the issue: plank performance and pain in the lower back

Key points

1. 01People with low back pain held significantly longer planks than pain-free adults, contradicting the common assumption that stronger anterior core endurance protects against back pain.
2. 02Plank duration alone was not an independent predictor of low back pain in logistic regression (p = 0.070).
3. 03Among people with low back pain, a higher bridge-to-plank ratio (more posterior chain endurance relative to anterior) was linked to lower self-reported disability (r = -0.31, p = 0.023).
4. 04The plank primarily activates superficial anterior muscles (rectus abdominis), not the deep spinal stabilizers most relevant to back pain.
5. 05Rehabilitation should address both anterior and posterior trunk musculature rather than relying on plank performance alone.

How it was conducted

Design

Cross-sectional study

Participants

117 adults aged 20-61 years (mean 26.0 +/- 9.3), including individuals with and without low back pain; 76 female, 41 male; primarily university students

Exposure measure

Prone plank endurance test (hold time in seconds until loss of neutral alignment or voluntary cessation)

Outcome measures

Modified Oswestry Disability Index (MODI); binary self-report of low back pain presence

Secondary analysis

54 participants with low back pain completed single-leg bridge tests; bridge-to-plank ratio calculated to assess posterior vs. anterior chain balance

Statistical analyses

Mann-Whitney U test, binary logistic regression, Pearson and Spearman correlations

What they found

• Individuals with low back pain held planks significantly longer than those without (U = 1861.00, z = 2.096, p = 0.036); effect size Cohen's d = -0.435 (small to moderate).
• Logistic regression model was statistically significant overall (chi-square = 12.39, p = 0.030), but plank duration was not an independent predictor of low back pain (B = 0.009, OR = 1.009, 95% CI 1.00-1.02, p = 0.070).
• Participants with low back pain were significantly older than those without (U = 1910.50, p = 0.015).
• Gender was not significantly associated with low back pain status (chi-square = 0.919, p > 0.05).
• Among 54 participants with low back pain, higher bridge-to-plank ratio was significantly associated with lower MODI disability scores (Pearson r = -0.31, p = 0.023; Spearman rho = -0.32, p = 0.018).
• Post hoc power analysis indicated approximately 75% power to detect a small to moderate group difference (Cohen's d approximately 0.37) at alpha = 0.05 with N = 117.

Limitations

• Cross-sectional design prevents any causal conclusions about the relationship between core endurance and low back pain.
• Sample was primarily young, physically active university students, limiting generalizability to older or more clinically diverse populations.
• Only a single plank trial was administered without familiarization or formal warm-up, which may have increased performance variability.
• Psychosocial factors such as fear-avoidance beliefs and pain duration were not assessed, despite being established contributors to disability in low back pain.

Why it matters

For patients

If you have low back pain, being able to hold a plank for a long time does not mean your back is healthier; building strength through hip and posterior chain exercises may do more to reduce disability than planks alone.

For clinicians

Plank duration should not be used as a standalone indicator of core health or low back pain risk; comprehensive assessment including posterior chain endurance and muscular balance is more clinically meaningful.

For readers

This study challenges a widely held assumption in rehabilitation and fitness, showing that anterior core endurance metrics can be misleading without considering the balance between front and back trunk musculature.