Blinding Assessment of Manual Therapy Interventions of the Back in Swiss Graduate Students

The Bang blinding index ranges from -1 to 1, with 0 representing satisfactory blinding. It can be interpreted as the proportion of participants correctly answering their allocated intervention within an intervention arm beyond chance. For the Bang BI, a score with an absolute value of ≤0.3 (i.e., -0.3 to 0.3) was deemed compatible with satisfactory blinding, although blinding scenarios (comparing blinding indices in active vs. control arms) were discussed.

Participants were asked: "To which extent do you know which intervention you received?" and were given five possible answers: "I strongly believe I received the active intervention", "I somewhat believe I received the active intervention", "I somewhat believe I received the control intervention", "I strongly believe I received the control intervention", and "I do not know [whether I received the active or control intervention]".

The James blinding index ranges from 0 (all correct responses) to 1 (all 'don't know' responses), where 0.5 corresponds to 50% of responses being correct, and 50% incorrect. Lack of satisfactory blinding may be claimed if the two-sided confidence interval of the James blinding index does not cover 0.5.

Immediately after the intervention, participants rated their perception about received intervention on a five-point scale: "I strongly believe I received the active intervention", "I somewhat believe I received the active intervention", "I somewhat believe I received the control intervention", "I strongly believe I received the control intervention", and "I do not know [whether I received the active or control intervention]".

The Bang blinding index ranges from -1 to 1, with 0 representing satisfactory blinding. It can be interpreted as the proportion of outcome assessors who correctly answered the allocated intervention of participants within an intervention arm beyond chance.

Outcome assessors were asked, "To which extent do you know which intervention (active intervention or control intervention) the patient received?" on a five-point scale: "I strongly believe that they received the active intervention," "I somewhat believe that they received the active intervention," "I somewhat believe that they received the control intervention," "I strongly believe that they received the control intervention," "I don't know [whether this participant received active or control intervention]."

Factors contributing to perceived intervention arm allocation among study participants were explored with an open-ended free text question: "Please briefly explain your answer regarding the question above [question above: "To which extent do you know which intervention you received?"].

Factors contributing to perceived intervention arm allocation among outcome assessors were explored with an open-ended free text question: "Please briefly explain your answer regarding the question above [question above: "To which extent do you know which intervention (active intervention or control intervention) the patient received?"].

The James blinding index ranges from 0 (all correct responses) to 1 (all 'don't know' responses), where 0.5 corresponds to 50% of responses being correct, and 50% incorrect. Lack of satisfactory blinding may be claimed if the two-sided confidence interval of the James blinding index does not cover 0.5.

Outcome assessors were asked, "To which extent do you know which intervention (active intervention or control intervention) the patient received?" on a five-point scale: "I strongly believe that they received the active intervention," "I somewhat believe that they received the active intervention," "I somewhat believe that they received the control intervention," "I strongly believe that they received the control intervention," "I don't know [whether this participant received active or control intervention]."

Participants answered the question, "How would you rate your back flexibility at the moment?" (adapted from The International Fitness Scale [IFIS]). Possible answers (5-point scale) include "Very poor," "Poor," "Average," "Good," and "Very good."

Participants answered the question, "How would you rate your back flexibility at the moment?" (adapted from The International Fitness Scale [IFIS]). Possible answers (5-point scale) include "Very poor," "Poor," "Average," "Good," and "Very good."

Ache, pain, discomfort in the upper back by asking, "During the past week, have you experienced ache, pain, discomfort in your upper back?". If answered "Yes," participants were asked to rate the degree of discomfort: "How uncomfortable do you feel with the ache, pain, or discomfort in your upper back?". These two questions were adapted from the Cornell Musculoskeletal Discomfort Questionnaire.

Ache, pain, discomfort in the upper back by asking, "During the past week, have you experienced ache, pain, discomfort in your upper back?". If answered "Yes," participants were asked to rate the degree of discomfort: "How uncomfortable do you feel with the ache, pain, or discomfort in your upper back?". These two questions were adapted from the Cornell Musculoskeletal Discomfort Questionnaire.

Ache, pain, discomfort in the lower back by asking, "During the past week, have you experienced ache, pain, discomfort in your lower back?". If answered "Yes," participants were asked to rate the degree of discomfort: "How uncomfortable do you feel with the ache, pain, or discomfort in your lower back?". These two questions were adapted from the Cornell Musculoskeletal Discomfort Questionnaire.

Ache, pain, discomfort in the lower back by asking, "During the past week, have you experienced ache, pain, discomfort in your lower back?". If answered "Yes," participants were asked to rate the degree of discomfort: "How uncomfortable do you feel with the ache, pain, or discomfort in your lower back?". These two questions were adapted from the Cornell Musculoskeletal Discomfort Questionnaire.

Maximum active total flexion and extension (0 to 100+ degrees) in standing position, measured with a validated mobile phone measuring device placed at the level of T12. Higher scores represent higher flexibility.

Maximum active total flexion and extension (0 to 100+ degrees) in standing position, measured with a validated mobile phone measuring device placed at the level of T12. Higher scores represent higher flexibility.

Change in maximum active total flexion and extension (0 to 100+ degrees) in standing position, measured with a validated mobile phone measuring device placed at the level of T12. Higher scores represent higher flexibility.