Outcomes	Illustrative comparative risks (95% CI)		Relative effect (95% CI)	No. of participants (studies)	Certainty of the evidence (GRADE)	Comments
	Assumed risk	Corresponding risk
	Placebo	Therapeutic ultrasound
Lumbar flexion ROM (mm; higher numbers mean increased ROM) Follow‐up: short term (post‐treatment)	The mean flexion ROM in the control group for the most representative study, Ebadi 2012, is 59.8 mm (SD 17.9).*	The mean flexion ROM in the intervention groups was 3.2 mm more (11.1 less to 17.5 more).	SMD 0.18 (−0.62 to 0.98	89 (3 RCTs)	⊕⊝⊝⊝ very low1,2,3	Corresponding risk calculated with an SMD of 0.18 (−0.62 to 0.98). Estimate is not clinically important and is very uncertain.
Lumbar extension ROM (mm; higher numbers mean increased ROM) Follow‐up: short term (post‐treatment)	The mean extension ROM in the control group for the most representative study, Ebadi 2012, is 24.1 mm (SD 9.3).*	The mean extension ROM in the intervention groups was 3.1 mm less (7.9 less to 1.8 more).	SMD −0.33 (−0.85 to 0.19	58 (2 RCTs)	⊕⊝⊝⊝ very low2,4	Corresponding risk calculated with an SMD of −0.33 (−0.85 to 0.19). Estimate is not clinically important and is very uncertain.
Muscle strength	No trials were identified that reported on this outcome.
Muscle endurance (Biering‐Sorensen test (seconds); higher numbers mean increased endurance) Follow‐up: short term (post‐treatment)	The mean muscle endurance in the control group was 139.3 seconds.	The mean muscle endurance in the intervention group was 11.0 seconds less (34.9 less to 12.9 more).	MD −11.00 (−34.94 to 12.94)	39 (1 RCT)	⊕⊕⊝⊝ low2	Estimate is not clinically important and suggests there may be little to no difference between groups.
*Of the trials included in this outcome, we chose the study that is a combination of the most representative study population and the lowest risk of bias (Ebadi 2012). This figure represents the mean outcome in the control group of this particular study. CI: confidence interval; MD: mean difference; RCT: randomised controlled trial; ROM: range of motion; SD: standard deviation; SMD: standardised mean difference
GRADE Working Group grades of evidence High certainty: Further research is very unlikely to change our confidence in the estimate of effect. Moderate certainty: Further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate. Low certainty: Further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate. Very low certainty: We are very uncertain about the estimate.