Patients will receive the same treatment in physical therapy than the control group and additionally they will receive CBT. The aim of the CBT intervention is to produce changes in the beliefs and behaviors about physical activity and avoidance of activity. The treatment's components are:

• Psychoeducation to counteract the misconceptions about low back pain and to point on the relevance of maintaining an adequate level of activity.
• Cognitive restructuring techniques
• Behavioural therapy and activity pacing
• Training on self-management pain techniques (mindfulness and relaxation). It is a 6-session group therapy, with one session per week. Each group will be composed by 6-8 participants. It will be considered as a patient who receives the treatment when the patient attends to the assessment sessions and to at least 4 out of 6 CBT sessions.

The patients of this group will receive the same interventions that the CBT group but will receive a reinforcements of the sessions' content through two different ways, both based on ICTs: a web tool named TEO (Emotional Therapy Online) specially designed to practicing the therapeutic strategies at home; and SMS that will send to the patients' mobile phone with reminders and reinforcements. The content of sessions will be related to the therapeutic components including on the CBT. Patients will access TEO from their home using a personal password. Besides TEO, messages will be sent through SMS three times per week during the treatment and once a week during the follow-up. The messages will consist on reminders to do the homework along with reinforcements of the working and effort made to improve their health.

Levels of anxiety and depression will be assessed by using the HADS questionnaire (Hospital Anxiety and Depression Score). This questionnaire is widely used in clinical practice. The HADS is a fourteen item scale where seven of the items are related to anxiety and the others seven are related to depression. The Spanish version has shown good internal consistency and external validity, as well as an adequate sensitivity in order to identify clinically significant depression.

The Fear-Avoidance Beliefs Questionnaire (FABQ) will be used to measure this domain. Is a scale composed by sixteen items developed to assess patients' beliefs and attitudes about the causes and consequences of their low back pain. Participants rate their agreement with each statement on a 7- point Likert scale (0 = completely disagree, 6 = completely agree). The FABQ consists of 2 subscales. The first sub-scale is the Physical Activity subscale (FABQpa), is composed by seven items, and assesses the effects of physical activities over pain. The second subscale is the Work subscale (FABQw) composed by four items, and it assesses the way that work activities can affect pain. The Spanish version has shown excellent psychometrics properties.

The Pain Catastrophizing Scale (PCS) assesses the tendency to consider pain as a threat with exaggerated negative consequence to the patient. It is a 13-item self-report scale, each item evaluate the pain experience, as an example: "I become afraid that the pain will get worse". Participants assess the frequency that these ideas appears, on a likert-type scale ranging from 0 to 4 being 0 "not at all" and 4 "all the time". The PCS yields a total score and three subscale scores assessing rumination, magnification and helplessness. A high score on the total PCS score indicates a high level of catastrophizing. The Spanish version of PCS has demonstrated adequate psychometrics properties.

The SF-12 is the brief version of the 36-item Short Form Health Survey (SF-36). The SF-12 contains items that measure each of the eight concepts included in the SF-36, namely physical functioning, role limitations due to physical health problems, bodily pain, general health, vitality (energy/fatigue), social functioning, role limitations due to emotional problems, and mental health (psychological distress and psychological well-being). The SF-12 contains six-point scales were patients evaluated the frequency and intensity of each statement during the past month.

Analysis of the barriers for the use of cognitive behavioral therapy and communication and information technologies in chronic low back pain treatment: This analysis includes 3 groups of patients, resulting from the three experimental conditions, compound of 8 patients each, selected by a balanced randomization to assure variability in gender, age, educational levels and level's use of information and communication technologies. We will apply a focus group strategy and it will be accomplished at the end of the therapy. The focus groups will be recorded and analyzed with qualitative analysis methodology. The clinic staff's opinion will be obtained on ad-hoc questionnaires and filled in by the clinicians.