title: Age and gender related neuromuscular changes in trunk flexion-extension.
abstract: BACKGROUND
  The root mean square surface electromyographic activity of lumbar extensor muscles during dynamic trunk flexion and extension from a standing position and task specific spine ranges of motion objectively assess muscle function in healthy young and middle age individuals. However, literature on neuromuscular activation and associated spine and hip kinematics in older individuals is sparse. This cross sectional study sought to examine the sex and age (<40 versus >60 years) related differences in the neuromuscular activation profiles of the lumbar extensors and the related spine and hip kinematics from healthy individuals during a standardized trunk flexion-extension task.
  
  
  METHODS
  Twenty five older (13 females, 60-90 years) and 24 younger (12 females, 18-40 years) healthy individuals performed trunk flexion-extension testing by holding static positions at half-flexion way and full range of motion between standing and maximum trunk flexion. The associated lumbar extensor muscle activity was derived from measurements at standing, half, and maximum flexion positions. The range of motion at the hip and lumbar spine was recorded using 3d accelerometers attached to the skin overlying the multifidus and semispinalis thoracis muscles lateral to the L5 and T4 spinous processes, respectively. Statistical calculations were performed using a permutation ANOVA with bootstrap confidence intervals.
  
  
  RESULTS
  The muscle activity in the half related to the maximum flexion position (half flexion relaxation ratio) was significantly smaller in older males when compared with younger males. Moreover, measurements revealed smaller activity changes from standing to the half and from half to the maximum flexion position in older compared to younger individuals. Older males displayed smaller gross trunk range of motion from standing to maximum flexion than any other group.
  
  
  CONCLUSIONS
  Gender and normal aging significantly affect both the activation patterns of the lumbar extensor muscles and the kinematics of the trunk during a standardized trunk flexion-extension task. Measurement results from healthy young and middle age individuals should not be used for the assessment of individuals older than 60 years of age.
authors.affiliation: Karl-Landsteiner-Institute for outpatient rehabilitation research, Vienna, Austria. kienbacher@rehabzentrum.at.
authors.forename: Thomas
authors.initials: T
authors.lastname: Kienbacher
authors.forename: Birgit
authors.initials: B
authors.lastname: Paul
authors.forename: Richard
authors.initials: R
authors.lastname: Habenicht
authors.forename: Christian
authors.initials: C
authors.lastname: Starek
authors.forename: Markus
authors.initials: M
authors.lastname: Wolf
authors.forename: Josef
authors.initials: J
authors.lastname: Kollmitzer
authors.forename: Patrick
authors.initials: P
authors.lastname: Mair
authors.forename: Gerold
authors.initials: G
authors.lastname: Ebenbichler
mesh_terms: D061725:Accelerometry; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology; D001696:Biomechanical Phenomena / Q000502:physiology*; D003430:Cross-Sectional Studies; D004576:Electromyography; D005260:Female; D006615:Hip / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000502:physiology; D006801:Humans; D008161:Lumbosacral Region / Q000294:innervation / Q000502:physiology; D008297:Male; D008875:Middle Aged; D009068:Movement / Q000502:physiology*; D053581:Muscle Strength Dynamometer; D018482:Muscle, Skeletal / Q000254:growth & development / Q000294:innervation* / Q000502:physiology*; D011877:Radionuclide Imaging; D012727:Sex Characteristics; D013131:Spine / Q000033:anatomy & histology / Q000294:innervation / Q000502:physiology; D013909:Thorax / Q000294:innervation / Q000502:physiology; D055815:Young Adult