title: Electromyography Activation of the Lower-Limb Muscles Adopting a Physioball and Elastic Band to Stabilize the Knee Joint During Multiple Sets With Submaximal Loads.
abstract: METHODS
  Crossover design.
  
  
  BACKGROUND
  Excessive valgus and varus force which affected the knee joint during dynamic tasks has been often associated to lower extremity injuries. Strategies to increase the resistance against these asymmetries (eg, the use of a physioball between the knees or elastic bands around the knees) are often applied in rehabilitation and conditioning programs.
  
  
  OBJECTIVE
  The purpose of this study was to investigate the effect of performing leg press (LP) 45° using a physioball and elastic band over multiple sets with submaximal loads on electromyographic (EMG) amplitude and fatigue indices.
  
  
  METHODS
  18 trained females volunteered (age: 24.4 ± 2.1 y; height: 168.1 ± 4 cm; body mass: 65.1 ± 4.4 kg) participated in this study. The 10 repetition maximum (RM) loads were determined for the LP. Then, 3 experimental protocols were followed in a randomized crossover design over 3 nonconsecutive days: control protocol-the participants performed 4 LP sets; physioball between knees-4 LP sets were performed with the physioball between the knees; elastic band-4 LP sets were performed with the elastic band involving the knees. Ten repetitions were performed during each set with 70% of 10-RM loads; EMG spectral indices (CRMS and Cf5) was collected from the biceps femoris (BF), vastus lateralis (VL), vastus medialis obliquus (VMO), and rectus femoris (RF) muscles.
  
  
  RESULTS
  Higher levels of CRMS and Cf5 were noted for RF, VL, and VM muscles using the physioball and elastic band when compared with control protocol, respectively. CRMS index of BF muscle was significantly higher using physioball and elastic band protocol versus control condition, respectively.
  
  
  CONCLUSIONS
  Therefore, both physioball and elastic band can be adopted during LP with the goal to reduce excessive varus and valgus forces, respectively, even performing consecutive sets with submaximal loads. Furthermore, this may be an interesting alternative to increasing quadriceps activation and improving the knee joint stabilization.
authors.forename: Gabriel Andrade
authors.initials: GA
authors.lastname: Paz
authors.forename: Jason
authors.initials: J
authors.lastname: DeFreitas
authors.forename: Marianna
authors.initials: M
authors.lastname: de Freitas Maia
authors.forename: Jurandir
authors.initials: J
authors.lastname: Silva
authors.forename: Vicente
authors.initials: V
authors.lastname: Lima
authors.forename: Humberto
authors.initials: H
authors.lastname: Miranda
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D018592:Cross-Over Studies; D004576:Electromyography; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000517:prevention & control*; D007719:Knee Joint / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D055070:Resistance Training / Q000295:instrumentation* / Q000379:methods; D055815:Young Adult
keywords: EMG; exercise performance; fatigue; rehabilitation; resistance training