We had many issues related to recruitment. After many attempts we want to suspend the study with 13 patients.

The aim of this trial is to investigate if patients treated by physical therapists who received an update on clinical practice guidelines and pain management have better outcomes than patients treated by physical therapists who did not received such training.

The training "Update on the treatment of patients with nonspecific chronic low back pain" will be announced in the social network by members of the study. Interested physical therapists will send an email to one of the study authors with their information regarding the inclusion criteria. After two months of notice, interested and eligible physiotherapists will be randomized into two groups of 15 participants each.

The study arms are: 1) control group (physical therapist who will not receive training) and 2) experimental group (physical therapist who will receive training). Before and after training, attitudes, beliefs and knowledge about low back pain guidelines will be evaluated.

Each physical therapist will recruit for the study a total of fifteen consecutive patients with chronic nonspecific low back pain (total sample=150 patients). All the patients will be assessed before the first session by a blinded examiner who will be unaware about the group allocation.

Clinical outcomes (pain, disability, fear avoidance beliefs and pain catastrophizing) will be collected at baseline and at 5 weeks, 3 and 6 months after randomization. All statistical analysis will be conducted following the principles of intention to treat analysis and the between-group differences will be performed using Mixed Linear Models.

Inclusion Criteria:

• patients seeking care for chronic non-specific low back pain (defined as pain or discomfort between the costal margins and the inferior gluteal folds, with or without referred symptoms in the lower limbs, for at least 3 months), with a pain intensity of at least 3 points measured by a 0-10 pain numerical rating scale, aged between 18 and 65 years.
• physiotherapists who treat exclusively patients with musculoskeletal pain, duly accredited by the National Council of Physical Therapy, physiotherapists offering private or medical insurance treatment individually to their patients, lasting 50-60 minutes each session, physiotherapists from 2 to five years of graduation and / or working in the area for the same period, that treat at least 2 patients with low back pain per month, and who are willing to treat at least 10 patients for the study.

Exclusion Criteria:

• patients will be excluded if they have any contraindication to physical exercise or ultrasound or short wave therapy, evidence of nerve root compromise (i.e one or more of motor, reflex or sensation deficit), serious spinal pathology (such as fracture, tumor, inflammatory and infectious diseases), serious cardiovascular and metabolic diseases, previous back surgery and pregnancy.
• physiotherapists who want to stop the activities for some reason that prevents participation in the study