title: Trunk muscle activation, fatigue and low back pain in tennis players.
abstract: OBJECTIVE
  To analyze differences in trunk endurance time, fatigue and activation in tennis players with and without low back pain.
  
  
  METHODS
  Observational study, cross-sectional design.
  
  
  METHODS
  Thirty-five tennis players completed an isometric trunk endurance protocol comprising four tasks (flexor, extensor and side bridge tests). LBP history was obtained through the Nordic Musculoskeletal Questionnaire. Endurance time was recorded for each test. Surface electromyographic activity was recorded bilaterally from rectus abdominis, external obliques, iliocostalis lumborum and longissimus thoracis. Average electromyographic amplitude and median frequency slopes during the tests were calculated and used as indicators of change in muscle activation and fatigue.
  
  
  RESULTS
  Asymptomatic players had greater flexor (p=0.004) and right side bridge (p=0.043) endurance times. These players produced a greater increase in avrEMG during the right side bridge test for the left ES-I (p=0.046) and right EO (p=0.008). Players with LBP in the last 7 days showed reduced activation of the left (p=0.014) and right (p=0.013) ES-I and left longissimus thoracis (ES-L, p=0.047) in the extensor test. In the left side bridge test there was a lower avrEMG slope of the left EO (p=0.024) and left RA MF slope (p=0.011). In the right side bridge test a lower left ES-I avrEMG slope was found (p=0.048).
  
  
  CONCLUSIONS
  Symptomatic players show lower activation of extensor muscles, less co-contraction patterns and less abdominal endurance. Tennis coaches and clinicians should consider these factors in their approach to players with LBP.
authors.affiliation: Laboratory of Motor Behavior, CIPER, Faculdade de Motricidade Humana, Universidade de Lisboa, Portugal. Electronic address: jpcorreia.ft@gmail.com.
authors.forename: José Pedro
authors.initials: JP
authors.lastname: Correia
authors.affiliation: Laboratory of Motor Behavior, CIPER, Faculdade de Motricidade Humana, Universidade de Lisboa, Portugal.
authors.forename: Raul
authors.initials: R
authors.lastname: Oliveira
authors.affiliation: Laboratory of Motor Behavior, CIPER, Faculdade de Motricidade Humana, Universidade de Lisboa, Portugal.
authors.forename: João Rocha
authors.initials: JR
authors.lastname: Vaz
authors.affiliation: Laboratory of Motor Behavior, CIPER, Faculdade de Motricidade Humana, Universidade de Lisboa, Portugal.
authors.forename: Luís
authors.initials: L
authors.lastname: Silva
authors.affiliation: Laboratory of Motor Behavior, CIPER, Faculdade de Motricidade Humana, Universidade de Lisboa, Portugal.
authors.forename: Pedro
authors.initials: P
authors.lastname: Pezarat-Correia
mesh_terms: D000293:Adolescent; D000328:Adult; D056352:Athletes; D003430:Cross-Sectional Studies; D004576:Electromyography; D005260:Female; D006801:Humans; D007537:Isometric Contraction; D017116:Low Back Pain / Q000503:physiopathology*; D008297:Male; D018763:Muscle Fatigue; D018482:Muscle, Skeletal / Q000503:physiopathology*; D010807:Physical Endurance; D013715:Tennis / Q000502:physiology*; D060726:Torso / Q000503:physiopathology*; D055815:Young Adult
keywords: Abdominal; Activation; Electromyography; Endurance; Lumbar