Cho 2014.

Study characteristics
Methods	Study design: RCT Recruitment period: not reported Recruitment mode: the subjects had been diagnosed with acute LBP by specialists Statistical analysis: to examine differences between the 2 groups in accordance with the interventions, a paired t‐test was carried out. An independent t‐test was performed to compare the groups Sample size calculation: not reported
Participants	Sample size: total: 40; EG1: 20; EG2: 20 Setting: not reported Country: Republic of Korea Baseline characteristics Age in years, mean (SD): not reported, participants were in their 20s Sex, number (%) women: EG1: 0 (0%); EG2: 0 (0%) Duration of LBP: diagnosed with acute LBP, not further specified Inclusion criteria Acute LBP diagnosis from a specialist Exclusion criteria Problems other than LBP
Interventions	EG1: stretching Description: the stretching group repetitively stretched their lower extremity joints, trunk joints, and upper extremity joints. Materials/equipment: none Non‐exercise component: not reported Frequency and duration: 3 times per week, for 1 hour each time, for a total of 4 weeks. Warming‐up exercises for the first 10 minutes and cooling‐down exercises for the last 10 minutes, with stretching during the intervening 40‐minute period. Delivery: generic group exercise; supervision: not reported Provider: not reported EG2: Tai Chi Description: various motions, including ya ma boon jong, boong ri je an, baek hak yang si, su whi bi pa, nu seul y obo, je su sang se, and yeo bong sap ye. Participants performed this 20‐minute routine twice. Materials/equipment: no Non‐exercise component: not reported Frequency and duration: 3 times per week, for 1 hour each time, for a total of 4 weeks. Warming‐up exercises for the first 10 minutes and cooling‐down exercises for the last 10 minutes. Tai Chi during the intervening 40‐minute period. Delivery: generic group exercise; supervision: not reported Provider: not reported
Outcomes	Note: outcomes were not designated as major or minor outcomes Pain: VAS (0–10; converted to a 0–100 scale) Baseline, mean (SD): EG1: 34 (6); EG2: 31 (6) 4 weeks, mean (SD): EG1: 28 (5); EG2: 21 (5) Other: muscle activity by surface electromyography Adverse events: not reported
Notes	Authors' results and conclusions: Tai chi was effective in decreasing pain and muscle activity of males with LBP in their 20s. Review authors' note: only a minimal difference was detected that was not clinically relevant. It is unclear whether the statistical test was performed between groups at 4 weeks. Funding: not reported Declaration of interest: no official disclosure regarding potential conflicts of interest
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	High risk	Abstract states participants were randomly assigned, randomisation procedure not described.
Allocation concealment (selection bias)	Unclear risk	Not described.
Blinding All outcomes ‐ Participants	High risk	No mention of attempts to blind participants.
Blinding All outcomes ‐ Healthcare providers	High risk	2 active interventions.
Blinding All outcomes ‐ outcome assessors	High risk	The outcome measures were self‐reported and participants were unblinded.
Influence of co‐interventions	Unclear risk	Not reported.
Group similarity at baseline	Unclear risk	Only pain and muscle activity were reported.
Compliance	Unclear risk	Not reported.
Timing of outcome assessments	Unclear risk	Pre‐ and post‐treatment.
Incomplete outcome data (attrition bias) Dropouts – all outcomes	Unclear risk	Study does not report number of dropouts in each group.
Intention‐to‐treat‐analysis	Unclear risk	No flow chart or other description of the number of participants before and after treatment.
Selective reporting (reporting bias)	High risk	Study reported pain but not functional status. No protocol published.
Other bias	Unclear risk	No funding sources reported. No official disclosure regarding potential conflicts of interest.