Study type and sample selection

Analytical survey: a cross-sectional study involving 78 adolescent girls practicing intermediate and advanced classical ballet as members of the dance company Ballet Paraisópolis, which is located in the western region of São Paulo. The adolescents were divided into three groups according to their level of intensity persistent symptoms of low back pain in the previous 14 consecutive days, during a 3-month period of persistent pain symptoms (group 1: adolescents with mild low back pain [0–3 pain intensity, n = 21]; group 2: adolescents with moderate low back pain [4–6 pain intensity, n = 17]; group 3: adolescents with high low back pain [7–10 pain intensity, n = 20]) following the guidelines of the Spine Society [37]. The control group consisted of 20 adolescent dancers of classical ballet who did not have any symptom of low back pain.

The study procedure was reviewed and approved by the Departmental Research Committee of the University Santo Amaro-UNISA (registration number: 3.756.991), in accordance with the Helsinki Declaration and relevant guidelines and regulations. Prior to participation, all volunteers were provided with information about the study and given the opportunity to ask questions before providing written informed consent/assent, as well as parental consent when required.

The eligibility criteria were as follows: adolescents of classical ballet with and without low back pain, adolescents who indicated that they had pain (current) in the region of the lower back with constant symptoms in the previous 14 consecutive days, during a 3-month period of pain symptoms, minimum age of 12 years [29], regular enrollment in Ballet Paraisópolis, with a twice-a-week training frequency [30], and 1-year practice time [32, 38]. The exclusion criteria were as follows: pain with irradiation to the lower limbs, medication use for pain (current), neurological abnormalities [24], congenital diseases [28, 30], spinal disorders [29], and the presence of tumors (cancer) or infection [30]. In addition, fractures in the previous 6 months; vestibulocochlear diseases; uncontrolled cardiac and/or respiratory arrhythmias; convulsive and neurological syndromes; diabetic neuropathy, osteoarthritis and rheumatoid arthritis, and any functional limitation that requires assistance in moving around were regarded as exclusion criteria to avoid bias in the interpretation of the assessments [31].