Table 1: Baseline description of yoga trial participants included in mediation analyses.

Main cohortSaliva cohort
YogaStretchingSelf-careYogaStretchingSelf-care

Total, 787440575125
Demographics
 Age (yrs), mean (SD)47(9.5)49(10.1)51(8.4)49(8.9)50(9.5)52(7.9)
 Women, (%)53(67.9%)47(63.5%)23(57.5%)37(64.9%)31(60.8%)15(60.0%)
 College graduate, (%)49(62.8%)53(71.6%)24(60.0%)34(59.6%)37(72.5%)15(60.0%)
 White, (%)68(87.2%)65(87.8%)39(97.5%)49(86.0%)43(84.3%)25(100.0%)
 Family income > $45,000/yr, (%)76(97.4%)65(90.3%)34(87.2%)55(96.5%)46(92.0%)21(84.0%)
 Lifts 20 + pounds at job, (%)16(20.5%)19(25.7%)14(35.0%)13(22.8%)10(19.6%)9(36.0%)
Health behaviors
 Obese (BMI ), (%)21(26.9%)21(28.4%)14(35.0%)13(22.8%)13(25.5%)10(40.0%)
 Drank alcohol today, (%)16(28.1%)18(35.3%)10(40.0%)
 Smoked today, (%)1(1.8%)3(5.9%)1(4.0%)
 Took medication(s) today, (%)38(66.7%)36(70.6%)19(76.0%)
Back pain status
 Days of back pain in last 6 months, mean (SD)146(46.2)132(51.4)148(47.1)146(46.7)134(53.9)155(37.2)
 Bothersomeness score, mean (SD)4.8(1.8)4.4(2.0)4.8(2.5)4.8(1.6)4.3(1.9)5.0(2.6)
 Pain travels down the leg, (%)11(14.1%)11(14.9%)8(20.0%)10(17.5%)7(13.7%)5(20.0%)
Back-related dysfunction
 Roland-Morris Disability Questionnaire (RDQ), mean (SD)9.4(4.8)8.5(3.7)9.0(4.9)9.6(4.7)8.2(3.7)8.4(4.9)
Potential mediators at baseline
 Positively impacts cognitive appraisal
  Fear avoidance, mean (SD)31.5(6.8)32.0(7.1)32.0(6.3)31.3(6.5)31.9(7.3)32.9(6.9)
  Self-efficacy, mean (SD)6.1(1.9)6.4(1.6)6.6(1.6)6.2(1.9)6.5(1.4)6.9(1.5)
  Body awareness, mean (SD)44.1(8.7)41.0(8.6)43.9(6.9)44.2(9.1)42.4(9.0)43.5(7.0)
 Positively impacts affect and stress
  Psychological distress, mean (SD)67.3(6.9)67.4(7.8)66.8(6.7)67.5(6.9)65.7(7.8)67.4(6.1)
  Perceived stress, mean (SD)16.0(5.6)16.0(5.3)15.2(5.4)15.8(5.8)15.8(5.2)15.8(6.0)
  Positive states of mind, mean (SD)14.8(2.2)15.3(2.0)15.5(2.3)14.8(2.3)15.3(2.1)15.3(2.5)
  Back pain negatively impacts sleep, (%)44(56.4%)42(57.5%)24(60.0%)30(52.6%)25(50.0%)14(56.0%)
 Physical activity
  Hours of back exercise in the past week, mean (SD)0.38(0.58)0.27(0.40)0.43(0.49)0.36(0.47)0.29(0.41)0.41(0.39)
 Improves neuroendocrine function
  Salivary cortisol awakening response (log scale), mean (SD)0.8(1.3)1.1(1.0)0.7(1.3)
  Salivary DHEA diurnal average (log scale), mean (SD) (0.7) (0.8) (0.8)