Table 3.
Overview of significant and nonsignificant risk factors in meta-analyses
| Risk Factor | Study | Measurement technique | Effect size (95% CI) | Weight |
|---|---|---|---|---|
| Lateral flexion range of motion (ROM) | Adams et al [29] | Equipment: 3Space Isotrak device Method: Sensors on sacrum and L1 spinous process measured degree change between upright standing and max lateral flexion |
0.50 (0.29-0.86) | 65.06 |
| Kujala et al [35] | Equipment: Tape measure Methods: Difference between middle finger position on ipsilateral thigh to most distal position of middle finger achieved in max lateral flexion |
0.49 (0.14-1.74) | 17.71 | |
| Van Nieuwenhuyse et al [38] | Equipment: Tape measure Methods: Difference between middle finger position on ipsilateral thigh to most distal position of middle finger achieved in max lateral flexion |
0.17 (0.05-0.61) | 17.23 | |
| Overall effect size (I-squared = 15.9%, p = 0.304) | 0.41 (0.24-0.73, p = 0.002) | 100 | ||
| Lumbar lordosis | Adams et al [29] | Equipment: 3Space Isotrak device Method: Sensors on sacrum and L1 spinous process measured degrees of lordosis in upright standing |
0.56 (0.38-0.83) | 35.48 |
| Milgrom et al [37] | Equipment: Cybex (EDI 320) inclinometer Method: Inclinometer place over spinous process of L4 and lordosis angle measured relative to horizontal |
0.88 (0.48-1.62) | 18.37 | |
| Nissinen et al [39] | Equipment: Spinal pantograph Method: Spinal pantograph used to measure lordosis angle in an upright standing |
0.84 (0.61-1.16) | 46.15 | |
| Overall effect size (I-squared = 29.7%, p = 0.241) | 0.73 (0.55-0.98, p = 0.034) | 100 | ||
| Hamstring flexibility | Feldman et al [31] | Equipment: Goniometer Method: Supine position with hip at 90°, ipsilateral knee extended from 90° of flexion |
0.96 (0.94-0.98) | 99.92 |
| Kujala et al [35] | Equipment: Hydrogoniometer Method: Straight leg raise |
0.70 (0.20-2.45) | 0.04 | |
| Van Nieuwenhuyse et al [38] | Equipment: Inclinometer Method: Straight leg raise |
1.00 (0.31-3.2) | 0.04 | |
| Overall effect size (I-squared = 0%, p = 0.883) | 0.96 (0.94-0.98, p = 0.001) | 100 | ||
| Back muscle strength | Biering-Sorensen et al [30] | Equipment: Strain gauge dynamometer Methods: Device attached to shoulders of participant and the MVC of 3 attempts of extension in upright standing |
1.49 (0.70-3.16) | 71.35 |
| Gibbons et al [32] | Equipment: not clear Methods: Max isokinetic strength from forward flexion to upright standing |
1.81 (0.55-5.93) | 28.65 | |
| Overall effect size (I-squared = 0%, p = 0.788) | 1.58 (0.83-2.97, p = 0.160) | 100 | ||
| Back muscle fatigability | Adams et al [29] | Equipment: Stopwatch Methods: Biering-Sorensen test |
0.80 (0.60-1.07) | 42.59 |
| Biering-Sorensen et al [30] | Equipment: Stopwatch Methods: Biering-Sorensen test |
0.42 (0.16-1.14) | 16.57 | |
| Gibbons et al [32] | Equipment: Stopwatch Methods: Biering-Sorensen test |
0.85 (0.26-2.77) | 12.97 | |
| Kujala et al [35] | Equipment: Stopwatch Methods: Biering-Sorensen test |
1.87 (0.53-6.56) | 11.80 | |
| Luoto et al [36] | Equipment: Stopwatch Methods: Biering-Sorensen test |
0.29 (0.11-0.81) | 16.06 | |
| Overall effect size (I-squared = 41.2%, p = 0.147) | 0.68 (0.42-1.12 p = 0.160) | 100 | ||
| Lumbar flexion range of motion (ROM) | Adams et al [29] | Equipment: 3Space Isotrak device Method: Sensors on sacrum and L1 spinous process measured degree change between upright standing and max forward flexion sitting with legs extended |
1.25 (0.94-1.67) | 50.92 |
| Biering-Sorensen et al [30] | Equipment: Tape measure Method: Modified Schober |
2.59 (1.23-5.46) | 19.98 | |
| Feldman et al [31] | Equipment: Tape measure Method: Schober |
0.93 (0.45-1.93) | 20.43 | |
| Kujala et al [35] | Equipment: Tape measure Method: Modified Schober |
0.88 (0.25-3.07) | 8.67 | |
| Overall effect size (I-squared = 34%, p = 0.209) | 1.32 (0.89-1.96, p = 0.167) | 100 | ||
| Lumbar extension ROM | Adams et al [29] | Equipment: 3Space Isotrak device Method: Sensors on sacrum and L1 spinous process measured degree change between upright standing and max extension in prone position |
0.95 (0.67-1.34) | 45.69 |
| Kujala et al [35] | Equipment: Draughtsman’s flexible curve Method: Devices placed on spinous process of S2, L4, and T12 in prone position with max extension. Curve traced on paper then angle in degrees measured. |
1.19 (0.34-4.14) | 22.76 | |
| Van Nieuwenhuyse et al [38] | Equipment: none Method: passive extension of lower back measured as presence or absence of pain |
0.29 (0.12-0.70) | 31.55 | |
| Overall effect size (I-squared = 68.7%, p = 0.041) | 0.69 (0.31-1.55, p = 0.367) | 100 | ||
| Isometric abdominal strength | Biering-Sorensen et al [30] 0 | Equipment: Strain gauge dynamometer Methods: Device attached to shoulders of participant and the MVC of 3 attempts of flexion in upright standing |
1.20 (0.56-2.53) | 16.62 |
| Feldman et al [31] | Equipment: Hand held myometer Methods: Sit-up, stop midway then resistance applied to the sternum. Max force that participant could hold in that position recorded |
0.96 (0.69-1.34) | 83.38 | |
| Overall effect size (I-squared = 0%, p = 0.602) | 1.00 (0.73-1.35, p = 0.976) | 100 | ||
| Fingertip to floor distance | Biering-Sorensen et al [30] | Equipment: Tape measure Method: Distance from tips of the middle fingers to the ground during max forward bending with feet together and knees extended |
0.96 (0.40-2.28) | 0.13 |
| Feldman et al [31] | Equipment: Sit and reach box Method: Sitting with hips flexed and knees extended |
1.00 (0.97-1.03) | 99.53 | |
| Kujala et al [35] | Equipment: Tape measure Method: Distance from tips of the middle fingers to the ground during max forward bending with feet together and knees extended |
2.65 (0.75-9.37) | 0.06 | |
| Van Nieuwenhuyse et al [38] | Equipment: Tape measure Method: Distance from tips of the middle fingers to the ground during max forward bending with feet together and knees extended |
1.00 (0.55-1.81) | 0.28 | |
| Overall effect size (I-squared = 0%, p = 0.515) | 1.00 (0.97-1.03, p = 0.973) | 100 | ||
| Quadriceps flexibility | Feldman et al [31] | Equipment: Goniometer Method: Degrees of knee flexion in a prone position |
1.02 (0.92-1.13) | 62.13 |
| Kanchanomai et al [33] | Equipment: Goniometer Method: Stationary arm of device aligned with the lateral midline of the thigh, fulcrum is placed over the lateral epicondyle of the femur and the moving arm is aligned with the lateral midline of the fibula. Smaller degrees of knee flexion equated to tighter quadriceps |
1.71 (1.03-2.84) | 37.87 | |
| Overall effect size (I-squared = 73.9%, p = 0.050) | 1.24 (0.76-2.03, p = 0.389) | 100 | ||
| Erector spinae CSA | Fortin et al [40] | Equipment: 1.5 Tesla Magnetom SP 4000 magnetic resonance imager Method: T2-weighted techniques at L3-4 and L5-S1 |
-0.09 (-0.48-0.31) | 27.25 |
| Gibbons et al [32] | Equipment: 1.5 tesla Magnetom magnetic resonance imager Method: Slice thickness was 3 mm and gaps between the slices 0.3 mm at the L3-4 level. |
0.00 (-0.65-0.65) | 72.75 | |
| Overall effect size (I-squared = 0%, p = 0.823) | -0.06 (-0.40-0.28, p = 0.722) | 100 | ||
| Quadratus lumborum CSA | Gibbons et al [32] | Equipment: 1.5 tesla Magnetom magnetic resonance imager Method: Slice thickness was 3 mm and gaps between the slices 0.3 mm at the L3-4 level. |
2.96 (0.89-9.86) | 82.85 |
| Kountouris et al [34] | Equipment: MRI and imaging software Method: Axial MR images measured at L2 and L4 levels |
0.55 (0.03-10.37) | 17.15 | |
| Overall effect size (I-squared = 8%, p = 0.297) | 2.22 (0.63-7.74, p = 0.212) | 100 | ||
MVC max voluntary contraction, CSA cross sectional area, MRI magnetic resonance imaging