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Table 1 Differences between the initial and modified trial designs and precipitating reasons for the change

From: Short term treatment versus long term management of neck and back disability in older adults utilizing spinal manipulative therapy and supervised exercise: a parallel-group randomized clinical trial evaluating relative effectiveness and harms

Initial design Modified design Rationale
Three-arm trial (n = 300) two-arm trial (n = 200) Enrollment
• 36 weeks SMT + SRE (n = 88) • 36 weeks SMT + SRE (n = 100) Funding
• 12 weeks SMT + SRE (n = 124) • 12 weeks SMT + SRE (n = 100)  
• 36 weeks SRE alone (n = 88)   
n = 300 n = 200 (for primary and secondary aims 1–4) Enrollment
n = 18 (for additional secondary aims A-C) Funding
Randomization ratio 1:1.4:1 Final randomization ratio 1:1 Enrollment
Funding
Pertinent inclusion/exclusion criteria: Pertinent inclusion/exclusion criteria: Enrollment
• NDI and ODI ≥ 15% each at both baseline evaluations • NDI and ODI ≥ 10% each AND combined score of ≥ 25% at first baseline evaluation only
Functional outcomes: Functional outcomes: Funding
• short physical performance battery
• hand grip strength
• accelerometry • short physical performance battery
• postural sway • hand grip strength
• range of motion • accelerometry
• static endurance