title: Electromyogram features during linear torque decrement and their changes with fatigue.
abstract: OBJECTIVE
  Surface electromyogram (EMG) spike shape analysis (SSA) has recently been proposed as an adjunct tool to EMG time and frequency domain analysis to increase our knowledge of motor unit (MU) control strategies. The study was aimed to understand more in MU deactivation strategy during torque decrement, and its possible changes in fatigued muscle, using a combination of traditional time and frequency domain analysis and SSA techniques.
  
  
  METHODS
  EMG was detected from the biceps brachii of 11 untrained male subjects during static down-going ramp contractions (90-0% of the maximal voluntary contraction, MVC) under non-fatigued (DGR) and fatigued (FDGR) conditions. The root mean square (RMS) and mean frequency (MF), as well as SSA parameters, were calculated on 1-s EMG windows centred on each 10 % MVC step for both conditions.
  
  
  RESULTS
  In both the DGR and FDGR EMG-RMS, mean spike amplitude and mean spike slope decreased by 50 % in the 90-60 % MVC. The mean spike frequency also decreased by 50 % in the 30-10 % MVC. Except the "mean number of spikes per second" all the other estimated EMG parameters were significantly different during FDGR compared to DGR.
  
  
  CONCLUSIONS
  The dynamics of EMG parameters during torque decrement would support a MU deactivation strategy which relies more on MU de-recruitment in the high % MVC range and more on firing rate reduction in the low % MVC range. The adopted integrated approach to EMG signal processing could indicate that SSA is an important tool to disclose alterations in motor control due to fatigue.
authors: Department of Kinesiology, Faculty of Physiotherapy, University School of Physical Education, Wrocław, Poland.
authors: Renata
authors: R
authors: Andrzejewska
authors: Artur
authors: A
authors: Jaskólski
authors: Anna
authors: A
authors: Jaskólska
authors: Massimiliano
authors: M
authors: Gobbo
authors: Claudio
authors: C
authors: Orizio
mesh_terms: D000328:Adult; D006801:Humans; D008297:Male; D009119:Muscle Contraction; D018763:Muscle Fatigue; D018482:Muscle, Skeletal / Q000502:physiology*; D019415:Torque