Had good levels of internal and external validity because of they can guide therapists and patients considering treatment options for back pain
The trial included a number of features to minimize bias
They used true randomization, concealed allocation, blinded assessment, and an intention-to-treat analysis and achieved excellent follow-up.
The treatments were conducted by a single therapist who was properly trained to perform the interventions, and there was an excellent treatment adherence.
Not monitoring the home exercise program
Not blinding both therapist and patients to the treatment allocation
did not include a non-treatment or placebo control group
Have confounders such as regression to the mean, placebo effects, and natural history are very likely to occur similarly in both groups