title: Postural steadiness and weight distribution during tandem stance in healthy young and elderly adults.
abstract: BACKGROUND
  Tandem stance is a clinical measure of standing balance considered to assess postural steadiness in a heel-to-toe position by a temporal measurement. To our knowledge, no studies have evaluated the change of postural steadiness, expressed as force variability, over time. The objective of this paper is to investigate postural steadiness during 30 s of tandem stance in healthy elderly and young adults, and to explore the weight distribution between legs during tandem stance.
  
  
  METHODS
  A cross-sectional analysis comparing ground reaction forces and muscle activity in 26 healthy elderly adults (mean age 70.6 years) and 27 healthy young adults (mean age 30.0 years). Ground reaction forces beneath both feet and muscle activity of ankle muscles were recorded while the subjects performed 30 s of tandem stance during two conditions.
  
  
  RESULTS
  Two phases were identified in both groups: First a dynamic phase, a decrease in force variability during the first 3-4 s after foot placement, and thereafter a static phase, maintaining a certain level of force variability. Age-related changes were seen in the decrease in force variability (P<0.001) and ankle muscle activity (P<0.001). However, both groups placed more weight on the rear leg (P<0.001).
  
  
  CONCLUSIONS
  The first few seconds of tandem stance pose the greatest challenge to postural steadiness and influence the static phase. We suggest that the dynamic phase is the most crucial period of time for assessing balance requirements. Independent of age, tandem stance is not a task for equal weight bearing.
authors.affiliation: Department of Neurotec, Karolinska Institutet, Division of Physiotherapy, Motor Control and Physical Therapy Research Laboratory, 141 83 Huddinge, Sweden. erika.s.jonsson@neurotec.ki.se
authors.forename: Erika
authors.initials: E
authors.lastname: Jonsson
authors.forename: Ake
authors.initials: A
authors.lastname: Seiger
authors.forename: Helga
authors.initials: H
authors.lastname: Hirschfeld
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D000843:Ankle Joint / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D004856:Postural Balance / Q000502:physiology*; D011187:Posture / Q000502:physiology*; D011312:Pressure; D013314:Stress, Mechanical; D016474:Weight-Bearing / Q000502:physiology*