title: Muscle action pattern and knee extensor strength of older Tai Chi exercisers.
abstract: OBJECTIVE
  Tai Chi (TC) practice has been shown to improve leg muscle strength among elders. This study examined the leg muscle action patterns during a typical TC movement, and their relationship with knee extensor strength and knee flexion angle in single leg stance.
  
  
  METHODS
  Surface electromyography of four leg muscles and knee movement were recorded from 5 female elderly TC practitioners while performing a TC movement and normal walking, respectively. The maximum knee extensor strength was also measured. The duration and magnitude of electromyography were compared between the TC movement and walking, and were correlated with the knee extensor strength and knee flexion angle.
  
  
  RESULTS
  Ankle dorsiflexors and knee extensors were activated significantly longer and higher during the TC movement than during walking. The duration and magnitude of all four leg muscles during the TC movement were positively correlated with the knee extensor strength and knee flexion angle, and these correlations were stronger than during walking.
  
  
  CONCLUSIONS
  The TC movement puts more demand on ankle dorsiflexors and knee extensors that are not otherwise heavily recruited during walking. The degree of knee flexion during single leg stance of the TC movement may be a key element for improving leg muscle strength.
authors.affiliation: Department of Rehabilitation and Movement Science, The University of Vermont, Burlington, VT., USA.
authors.forename: Ge
authors.initials: G
authors.lastname: Wu
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000843:Ankle Joint / Q000502:physiology; D004576:Electromyography; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000502:physiology; D008875:Middle Aged; D053580:Muscle Strength / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D026302:Tai Ji; D016138:Walking / Q000502:physiology