title: Cross-talk in mechanomyographic signals from the forearm muscles during sub-maximal to maximal isometric grip force.
abstract: OBJECTIVE
  This study aimed: i) to examine the relationship between the magnitude of cross-talk in mechanomyographic (MMG) signals generated by the extensor digitorum (ED), extensor carpi ulnaris (ECU), and flexor carpi ulnaris (FCU) muscles with the sub-maximal to maximal isometric grip force, and with the anthropometric parameters of the forearm, and ii) to quantify the distribution of the cross-talk in the MMG signal to determine if it appears due to the signal component of intramuscular pressure waves produced by the muscle fibers geometrical changes or due to the limb tremor.
  
  
  METHODS
  Twenty, right-handed healthy men (mean ± SD: age  = 26.7±3.83 y; height  = 174.47±6.3 cm; mass  = 72.79±14.36 kg) performed isometric muscle actions in 20% increment from 20% to 100% of the maximum voluntary isometric contraction (MVIC). During each muscle action, MMG signals generated by each muscle were detected using three separate accelerometers. The peak cross-correlations were used to quantify the cross-talk between two muscles.
  
  
  RESULTS
  The magnitude of cross-talk in the MMG signals among the muscle groups ranged from, R2(x, y) = 2.45-62.28%. Linear regression analysis showed that the magnitude of cross-talk increased linearly (r2 = 0.857-0.90) with the levels of grip force for all the muscle groups. The amount of cross-talk showed weak positive and negative correlations (r2 = 0.016-0.216) with the circumference and length of the forearm respectively, between the muscles at 100% MVIC. The cross-talk values significantly differed among the MMG signals due to: limb tremor (MMGTF), slow firing motor unit fibers (MMGSF) and fast firing motor unit fibers (MMGFF) between the muscles at 100% MVIC (p<0.05, η2 = 0.47-0.80).
  
  
  CONCLUSIONS
  The results of this study may be used to improve our understanding of the mechanics of the forearm muscles during different levels of the grip force.
authors.affiliation: AI-Rehab Research Group, Universiti Malaysia Perlis (UniMAP), Arau, Perlis, Malaysia.
authors.forename: Md Anamul
authors.initials: MA
authors.lastname: Islam
authors.affiliation: AI-Rehab Research Group, Universiti Malaysia Perlis (UniMAP), Arau, Perlis, Malaysia.
authors.forename: Kenneth
authors.initials: K
authors.lastname: Sundaraj
authors.affiliation: AI-Rehab Research Group, Universiti Malaysia Perlis (UniMAP), Arau, Perlis, Malaysia.
authors.forename: R Badlishah
authors.initials: RB
authors.lastname: Ahmad
authors.affiliation: Medical Officer, Malaysian Ministry of Health, Klang, Selangor, Malaysia.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Sundaraj
authors.affiliation: AI-Rehab Research Group, Universiti Malaysia Perlis (UniMAP), Arau, Perlis, Malaysia.
authors.forename: Nizam Uddin
authors.initials: NU
authors.lastname: Ahamed
authors.affiliation: AI-Rehab Research Group, Universiti Malaysia Perlis (UniMAP), Arau, Perlis, Malaysia.
authors.forename: Md Asraf
authors.initials: MA
authors.lastname: Ali
mesh_terms: D000328:Adult; D004576:Electromyography / Q000379:methods; D005542:Forearm / Q000502:physiology*; D018737:Hand Strength / Q000502:physiology*; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D008297:Male; D053580:Muscle Strength / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D009213:Myography / Q000379:methods; D012044:Regression Analysis