Table 1 Demographic and baseline questionnaire data.

From: Feeling stiffness in the back: a protective perceptual inference in chronic back pain

Demographic variables Study 1a and 1b Study 2
CLBP & stiffness (n = 15) Healthy controls (n = 15) p-value CLBP & stiffness (n = 10) Healthy controls (n = 10) p-value
Age (years) 27.1 (8.3) 28.9 (8.3) 0.54 23.4 (4.8) 25.7 (5.4) 0.33
Gender 11M, 4F 10M, 5F 0.69 7M, 3F 6M, 4F 0.64
Height (cm) 176.5 (11.1) 170.2 (11.1) 0.14 176.0 (11.2) 170.5 (13.5) 0.33
Weight (kg) 74.5 (16.5) 73.5 (15.3) 0.85 73.1 (16.5) 71.3 (13.3) 0.80
Current pain 34.3 (15.5) 1.2 (2.2) <0.001 16.5 (18.4) 0.6 (1.6) 0.02
Avg pain last 48 hrs 36.7 (16.8) 0.6 (1.4) <0.001 23.0 (17.7) 0.6 (1.6) 0.003
Duration of pain (years) 6.4 (5.1) n/a n/a 6.2 n/a n/a
Current stiffness 43.0 (17.2) 2.0 (2.4) <0.001 20.8 (16.8) 1.2 (2.1) 0.005
Avg stiffness last 48 hrs 41.3 (19.3) 2.3 (3.7) <0.001 26.8 (19.2) 1.7 (3.3) 0.003
Body drawing (count)
 •  Complete/accurate 2 7 0.046 1 4 0.12
 •  Incomplete/inaccurate 13 8 9 6
Modified ODQ 31.2 (15.7) 1.3 (2.5) <0.001 22.0 (9.7) 0.4 (0.8) <0.001
Back Beliefs Questionnaire:
   Inevitability 29.9 (6.6) 29.9 (5.5) 0.77 20.3 (16.0) 20.9 (15.6) 0.74
State STAI-short form:
   Pre-testing 11.0 (4.0) 7.9 (1.7) 0.01 10.7 (4.1) 8.3 (2.1) 0.13
   Post-testing 9.9 (3.4) 7.6 (1.6) 0.03 10.4 (3.7) 7.7 (1.9) 0.06
  1. All values are mean (SD) unless otherwise specified. Pain and stiffness measures rated using a 0–100 numerical rating scale (NRS), where higher values represent more pain/stiffness. Body image drawings of the back assessed perception of the back32 and were coded as either complete/accurate or incomplete (missing parts of the back) or inaccurate (large deviations in drawing of the back). Modified Oswestry Disability Questionnaire (ODQ) has a minimum score of 0 and a total possible score of 100, higher scores represent higher levels of disability67. Back Beliefs Questionnaire has a minimum score of 9 and maximum score of 45 where lower scores represent increased negativity in back beliefs68. Spielberg State-Trait Anxiety Inventory (STAI) short form has a minimum score of 6 and a maximum score of 24; higher scores indicate higher levels of state anxiety69.