Trunk sway measures of postural stability during clinical balance tests: Effects of age

Background. The major disadvantage of current clinical tests that screen fo r balance disorders is a reliance on an examiner's subjective assessment of equilibrium control. To overcome this disadvantage we investigated. using quantified measures of trunk sway, age-related differences of normal subjec ts for commonly used clinical balance tests. Methods. Three age groups were tested: young (15-25 years: n = 48), middle- aged (45-55 years: n = 50) and elderly (65-75 years: n = 49). Each subject performed a series of fourteen tasks similar to those included in the Tinet ti and Clinical Test of Sensory interaction in Balance protocols. The test battery comprised stance and gait tasks performed under normal, altered vis ual (eyes closed), and altered proprioceptive: (foam support surface) condi tions. Quantification of trunk sway was performed using a system that measu red trunk angular velocity and position in the roll (lateral) and pitch (fo re-aft) planes at the level of the lower hack. Ranges of sway amplitude and velocity were examined for age-differences with ANOVA techniques. Results. A comparison between age groups showed several differences. Elderl y subjects were distinguished from both middle-aged and young subjects by t he range of trunk angular sway and angular velocity because both were great er in roll and pitch planes for stance and stance-related tasks (tandem wal king). The most significant apr group differences (F = 30. p < .0001) were found for standing on one leg on a normal floor or on a foam support surfac e with eyes open. Next in significance wa walking eight tandem steps on a n ormal floor (F = 13.p < .0001). For gait tasks. such as walking five steps while rotating or pitching the head or with eyes closed, pitch and roll vel ocity ranges were influenced by age with middle-aged subjects showing the s mallest ranges followed by elderly subjects and then young subjects (F = 12 , p < .0001). Walking over a set of low barriers also yielded significant d ifferences between age groups for duration and angular sway. In contrast. t ask duration was the only variable significantly influenced when walking up and down a set of stairs. An interesting finding for all tasks was the dif ferent spread of values for each population. Population distributions were skewed for all ages and broadened with age. Conclusions. Accurate measurement of trunk angular sway during stance and g ait tasks provides a simple way of reliably measuring changes in balance st ability with age and could prove useful when screening for balance disorder s of those prone to fall.