Objective: To evaluate submaximal exercise tolerance and respiratory muscle strength in relation to forward head
posture (FHP) and respiratory mode in children, comparing mouth-breathing (MB) children with nasal-breathing
(NB) children. Methods: This was a controlled, analytical cross-sectional study involving children in the 8-12 year
age bracket with a clinical otorhinolaryngology diagnosis of MB, recruited between October of 2010 and January
of 2011 from the Mouth Breather Clinic at the State University of Campinas Hospital de Clínicas, located in the
city of Campinas, Brazil. The exclusion criteria were obesity, asthma, chronic respiratory diseases, heart disease,
and neurological or orthopedic disorders. All of the participants underwent postural assessment and the six-minute
walk test (6MWT), together with determination of MIP and MEP. Results: Of the 92 children in the study,
30 presented with MB and 62 presented with NB. In the MB group, the differences between those with moderate
or severe FHP and those with normal head posture, in terms of the mean MIP, MEP and six-minute walk distance
(6MWD), were not significant (p = 0.079, p = 0.622, and p = 0.957, respectively). In the NB group, the mean values
of MIP and MEP were higher in the children with moderate FHP than in those with normal head posture (p = 0.003
and p = 0.004, respectively). The mean MIP, MEP, and 6MWD were lower in the MB group than in the NB group.
Values of MIP and MEP were highest in the children with moderate FHP. Conclusions: Respiratory biomechanics
and exercise capacity were negatively affected by MB. The presence of moderate FHP acted as a compensatory
mechanism in order to improve respiratory muscle function.