Introduction: there is a lack of evidence with objective measurements of respiratory muscle tone in premature infants with bronchopulmonary dysplasia BPD. Objective: to assess the muscle tone of accessory inspiratory muscles in premature infants with and without BPD from birth to 36 gestational weeks. Material and method: a longitudinal observational clinical study with 37 premature infants of less than 36 weeks of gestational age and weighing less than 1500 grams, hospitalized at the neonatal intensive care unit. Premature infants underwent assessments of muscle tone with surface electromyography every two weeks after birth, on the muscles: pectoralis major, anterior serratus, trapezius, and erector of the spine. Those with severe complications, deaths and fewer than three surface electromyography measures were excluded. Premature infants were allocated into two groups: premature infants with bronchopulmonary dysplasia (with BPD, defined by the need for supplemental oxygen for 28 days or more) and control group, without BPD. Results: premature infants with bronchopulmonary dysplasia presented higher muscle tone in trapeziusin the 1st, 2nd, 3rd and 4th evaluations, in anterior serratus only in the 1st evaluation and inerector of the spine in the 2nd and in the 4th evaluations, compared to CG (p < 0.05 for all). In the intragroup analysis, the muscle tone of erector of the spine decreased over time in both groups (p < 0.05). In addition, infants with BPD required more invasive and non-invasive ventilatory support compared to CG (p < 0.05 for all). Conclusion: premature infants with BPD exhibit heightened muscle tone in accessory inspiratory muscles and elevated requirement for ventilatory support during the hospitalization in the neonatal intensive care unit.