Table 2

Trial-level and group-level characteristics for 27 IPD included studies compared with 29 eligible trials that did not provide data

Trial characteristicsIncluded IPD trials (n=27)
n (%)
Not included eligible trials (n=29)
n (%)
Median number of subjects (IQR)109 (65–209)90 (60–132)
Population source
 Healthcare16 (59)20 (69)
 Occupational5 (19)2 (7)
 General or mixed6 (22)7 (24)
Mean age of sample, years (95% CI)45.7 (45.2 to 46.1)42.9 (40.1 to 45.6)
Proportion of female sample (95% CI)55.5 (53.9 to 57.2)44.3 (36.0 to 52.7)
Mean severity of pain at baseline (95% CI)53.5 (52.6 to 54.3)50.9 (44.6 to 57.1)
Number of exercise groups available
 1 exercise group11 (41)11 (46)
 2 exercise groups13 (48)15 (63)
 3 exercise groups3 (11)3 (13)
Number of comparison groups available
 1 comparison group13 (48)15 (63)
 2 comparison groups2 (7)1 (4)
Exercise group types (46 groups)
 Strengthening4 (9)5 (8)
 Stretching1 (2)2 (3)
 Core strengthening10 (22)10 (15)
 Flexibility/mobilising1 (2)0 (0)
 Aerobic4 (9)2 (3)
 McKenzie2 (4)0 (0)
 Functional restoration1 (2)1 (2)
 Yoga0 (0)5 (8)
 Other4 (9)0 (0)
 Mixed (>2 types)19 (41)25 (37)
Design of exercise programme
 Individualised15 (33)6 (12)
 Partially individualised21 (46)18 (36)
 Standardised9 (20)26 (52)
 Not specified1 (2)0 (0)
Delivery of exercise programme
 Independent5 (11)1 (2)
 Independent with FU2 (4)1 (2)
 Group18 (39)30 (60)
 One-on-one17 (37)16 (32)
 Not specified4 (9)2 (4)
Comparison group types (17 groups)
No treatment/usual care comparisons7 (41)4 (24)
 No treatment3 (18)2 (12)
 Usual care4 (24)2 (12)
Other conservative treatment comparisons10 (59)13 (77)
 Advice/education5 (29)5 (29)
 Back school1 (6)0 (0)
 Electrotherapy0 (0)4 (24)
 Manual therapy3 (18)1 (6)
 NSAIDs/analgesics0 (0)1 (6)
 Physiotherapy0 (0)1 (6)
 Psychological therapy1 (6)0 (0)
 Relaxation0 (0)1 (6)
  • Data presented describe the number and percentage for each characteristic unless otherwise noted.

  • FU, follow-up; IPD, individual participant data; NSAIDs, non-steroidal anti-inflammatory drugs.