Testing walking performance in patients with low back pain: will two minutes do instead of six?

Key points

1. 01Distance over the first two minutes correlated highly with the full six-minute distance (r = 0.83, 95% CI 0.76 to 0.87).
2. 02Tripling the two-minute distance overestimated the observed six-minute distance by 46.8 meters on average, roughly 9%.
3. 03Both tests separated patients with high versus low disability, pain, and fear avoidance about equally well.
4. 04Neither test could tell apart subgroups based on sex, age, or BMI, suggesting disability and pain drive walking more than these factors in low back pain.
5. 05Walking distance correlated only weakly to moderately with self-reported disability and pain, so the tests add information rather than duplicating questionnaires.

How it was conducted

Design

Cross-sectional study using data from a questionnaire validation study in patients with persistent low back pain

Participants

124 outpatients with low back pain, aged 18 to 65, recruited at a Danish spine centre

Tests compared

Distance in the first two minutes of the six-minute walk test (2MWT#) versus the full six-minute walk test (6MWT), measured in a single session

Secondary outcomes

30-second sit-to-stand, Oswestry Disability Index, low back and leg pain intensity (NRS), fear avoidance (FABQ)

Analysis

Pearson correlation, predicted distance as three times the two-minute distance, Wilcoxon rank sum test for subgroups

What they found

• Two-minute and six-minute distances correlated highly: r = 0.83 (95% CI 0.76 to 0.87).
• Mean distance was 176.5 meters for the two-minute test and 482.6 meters for the six-minute test; mean predicted six-minute distance was 529.5 meters.
• The two-minute test overestimated the six-minute result by 46.8 meters (9%), SD 67.0 meters.
• Correlations with the sit-to-stand test were 0.50 (95% CI 0.36 to 0.62) for the two-minute test and 0.68 (0.57 to 0.76) for the six-minute test.
• Correlations with the Oswestry Disability Index were -0.45 (-0.58 to -0.30) for the two-minute test and -0.58 (-0.69 to -0.45) for the six-minute test.
• For high versus low disability (ODI), the six-minute test discriminated by 23% versus 19% for the two-minute test, both p < .01.
• No significant differences in either test by sex (p = 0.46 and 0.37), age cut-off 55 (p = 0.19 and 0.34), or BMI cut-off 30 (p = 0.13 and 0.07).
• Mean sample values: age 46.3 years, ODI 30.4%, low back pain 4.8 NRS, leg pain 3.5 NRS, fear avoidance 4.0 NRS.

Limitations

• The two-minute result was a split-time taken from within the six-minute test, not a standalone test, so some patients may have paced differently than they would in a true two-minute test.
• Patients on social benefits and those over 65 were excluded, so results may not apply to all low back pain patients.
• Specific pain causes such as disc herniation or stenosis were not distinguished, though they likely affect walking and the two-to-six-minute translation.
• Details on rest breaks during the test were not recorded, which could have explained why the correlation was not near-perfect as in some other populations.

Why it matters

For patients

If you have low back pain, a two-minute walk test can gauge your walking ability with much less time and effort than the longer six-minute version.

For clinicians

The two-minute walk distance is a valid, lower-burden substitute for the six-minute walk test in low back pain, but do not simply triple it to estimate the six-minute distance because that inflates the result by about 9%.

For readers

A quick walking test can flag impaired function and distinguish more from less disabled patients with low back pain nearly as well as a test three times as long.