title: Reduced complexity of force and muscle activity during low level isometric contractions of the ankle in diabetic individuals.
abstract: BACKGROUND
  This study evaluated the structure and amount of variability of surface electromyography (sEMG) patterns and ankle force data during low-level isometric contractions in diabetic subjects with different degrees of neuropathy.
  
  
  METHODS
  We assessed 10 control subjects and 38 diabetic patients, classified as absent, mild, moderate, or severe neuropathy, by a fuzzy system based on clinical variables. Multichannel sEMG (64-electrode matrix) of tibialis anterior and gastrocnemius medialis muscles were acquired during isometric contractions at 10%, 20%, and 30% of the maximum voluntary contraction, and force levels during dorsi- and plantarflexion were recorded. Standard deviation and sample entropy of force signals were calculated and root mean square and sample entropy were calculated from sEMG signals. Differences among groups of force and sEMG variables were verified using a multivariate analysis of variance.
  
  
  RESULTS
  Overall, during dorsiflexion contractions, moderate and severe subjects had higher force standard deviation and moderate subjects had lower force sample entropy. During plantarflexion, moderate subjects had higher force standard deviation and all diabetic subjects had lower entropy. Tibialis anterior presented higher root mean square in absent group and lower entropy in mild subjects. For gastrocnemius medialis, entropy was higher in severe and lower in moderate subjects.
  
  
  CONCLUSIONS
  Diabetic neuropathy affects the complexity of the neuromuscular system during low-level isometric contractions, reducing the system's capacity to adapt to challenging mechanical demands. The observed patterns of neuromuscular complexity were not associated with disease severity, with the majority of alterations recorded in moderate subject.
authors.affiliation: Laboratory of Biomechanics of Human Movement, Dept. Physical Therapy, Speech and Occupational Therapy, School of Medicine, University of Sao Paulo, Sao Paulo, Brazil.
authors.forename: E Y
authors.initials: EY
authors.lastname: Suda
authors.affiliation: SMI, Department of Health Science and Technology, Faculty of Medicine, Aalborg University, Denmark.
authors.forename: P
authors.initials: P
authors.lastname: Madeleine
authors.affiliation: SMI, Department of Health Science and Technology, Faculty of Medicine, Aalborg University, Denmark.
authors.forename: R P
authors.initials: RP
authors.lastname: Hirata
authors.affiliation: SMI, Department of Health Science and Technology, Faculty of Medicine, Aalborg University, Denmark.
authors.forename: A
authors.initials: A
authors.lastname: Samani
authors.affiliation: Laboratory of Biomechanics of Human Movement, Dept. Physical Therapy, Speech and Occupational Therapy, School of Medicine, University of Sao Paulo, Sao Paulo, Brazil.
authors.forename: T T
authors.initials: TT
authors.lastname: Kawamura
authors.affiliation: Laboratory of Biomechanics of Human Movement, Dept. Physical Therapy, Speech and Occupational Therapy, School of Medicine, University of Sao Paulo, Sao Paulo, Brazil. Electronic address: icnsacco@usp.br.
authors.forename: I C N
authors.initials: IC
authors.lastname: Sacco
mesh_terms: D000328:Adult; D000368:Aged; D000843:Ankle Joint / Q000503:physiopathology*; D001696:Biomechanical Phenomena; D003929:Diabetic Neuropathies / Q000503:physiopathology*; D004566:Electrodes; D004576:Electromyography; D005260:Female; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D053580:Muscle Strength / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*
keywords: Complexity; Diabetic neuropathies; Force; High-density EMG; Sample entropy