title: Older adults exhibit a reduced ability to fully activate their biceps brachii muscle.
abstract: BACKGROUND
  Voluntary muscle strength declines significantly in older adults. One contributing factor to the strength loss is muscle atrophy developed in old age. Whether the ability to maximally activate the muscle decreases with age, however, is unknown. This study was intended to determine if the central nervous system command to maximally activate the biceps brachii muscle deteriorates with age.
  
  
  METHODS
  Electrical stimulation pulses were applied to the skin overlying the biceps brachii muscle during maximal voluntary elbow-flexion contractions. The magnitude of force evoked on the maximal voluntary force was measured to determine the activation level (AL) of the muscle.
  
  
  RESULTS
  The AL was 94% for the elderly group and 97% for the young group (100% AL indicates complete activation). The AL for both the elderly and young groups was significantly (p<.05) lower than 100%. The AL of the elderly group was significantly (p<.05) lower than that of the young group.
  
  
  CONCLUSIONS
  The loss of voluntary strength in older adults is a mixed result of muscle atrophy and a reduced ability to fully activate muscle.
authors.affiliation: Department of Biomedical Engineering, The Cleveland Clinic Foundation, OH 44195, USA. yue@bme.ri.ccf.org
authors.forename: G H
authors.initials: GH
authors.lastname: Yue
authors.forename: V K
authors.initials: VK
authors.lastname: Ranganathan
authors.forename: V
authors.initials: V
authors.lastname: Siemionow
authors.forename: J Z
authors.initials: JZ
authors.lastname: Liu
authors.forename: V
authors.initials: V
authors.lastname: Sahgal
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D001132:Arm / Q000502:physiology*; D001284:Atrophy; D002490:Central Nervous System / Q000502:physiology; D004558:Electric Stimulation; D019054:Evoked Potentials, Motor / Q000502:physiology; D005260:Female; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D008297:Male; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology*; D009991:Oscillometry / Q000295:instrumentation; D012815:Signal Processing, Computer-Assisted