title: Electromyographic fatigue of orbicular oris muscles during exercises in mouth and nasal breathing children.
abstract: OBJECTIVE
  To investigate the process of fatigue in orbicularis oris muscles by analyzing the median frequency of electromyographic signal and the referred fatigue time, according to the breathing mode and the facial pattern.
  
  
  METHODS
  The participants were 70 children, aged 6 to 12 years, who matched the established criteria. To be classified as 36 nasal-breathing and 34 mouth-breathing children, they underwent speech-language, otorhinolaryngologic, and cephalometric evaluation. For the electromyographic assessment, the children had to sustain lip dumbbells weighing 40, 60, and 100 g and a lip exerciser, until the feeling of fatigue. Median frequency was analyzed in 5, 10, 15, and 20 seconds of activity. The referred time of the feeling of fatigue was also recorded. Data were analyzed through the analysis of variance--repeated measures (post hoc Tukey's test), Kruskal-Wallis test, and Mann-Whitney U-test.
  
  
  RESULTS
  A significant decrease in the median frequency from 5 seconds of activity was observed, independently from the comparison between the groups. On comparison, the muscles did not show significant decrease. The reported time for the feeling of fatigue was shorter for mouth-breathing individuals. This feeling occurred after the significant decrease in the median frequency.
  
  
  CONCLUSIONS
  There were signals that indicated myoelectric fatigue for the orbicularis oris muscles, in both groups analyzed, from the first 5 seconds of activity. Myoelectric fatigue in the orbicularis oris muscles preceded the reported feeling of fatigue in all groups. The account for fatigue time was influenced by only the breathing pattern, occurring more precociously in mouth-breathing children.
authors.affiliation: Special Coordination of Speech-Language Pathology and Audiology, Universidade Federal de Santa Catarina, Florianópolis, SC, Brazil.
authors.forename: Angela Ruviaro
authors.initials: AR
authors.lastname: Busanello-Stella
authors.affiliation: Special Coordination of Speech-Language Pathology and Audiology, Universidade Federal de Santa Catarina, Florianópolis, SC, Brazil.
authors.forename: Ana Paula
authors.initials: AP
authors.lastname: Blanco-Dutra
authors.affiliation: Department of Physical Therapy, Universidade Federal de Santa Maria, Santa Maria, RS, Brazil.
authors.forename: Eliane Castilhos Rodrigues
authors.initials: EC
authors.lastname: Corrêa
authors.affiliation: Universidade Federal de Santa Maria, Santa Maria, RS, Brazil.
authors.forename: Ana Maria Toniolo da
authors.initials: AM
authors.lastname: Silva
mesh_terms: D002648:Child; D004576:Electromyography; D005152:Facial Muscles; D005260:Female; D006801:Humans; D008297:Male; D009055:Mouth / Q000503:physiopathology*; D009058:Mouth Breathing / Q000503:physiopathology*; D018763:Muscle Fatigue; D011187:Posture; D012119:Respiration; D012129:Respiratory Function Tests / Q000295:instrumentation*