Biomedical subjects

Elizabeth T Hsiao-Wecksler

Publications and source records attributed to Elizabeth T Hsiao-Wecksler.

4 recordsLinked to original sources

PubMed2006

Effect of Tai Chi on gait and obstacle crossing behaviors in middle-aged adults.

This study investigated whether long-term, habitual practice of Tai Chi (or Taiji) results in behavioral modifications during gait. Specifically, we examined whether Tai Chi (TC) experience alters gait behavior during normal and obstructed walking. Fifteen experienced TC practitioners and fifteen control subjects (average age 45 years, 23-66 year range) completed level walking trials with or without a stationary obstacle placed in their path. TC practitioners in this study had an average of 6.5 years (1.5-15 year range) of Chen-style Tai Chi experience. Kinematic analyses performed on their step-to-step gait characteristics over multiple steps revealed that TC practitioners used a more cautious strategy by using slower gait speeds and shorter and slower steps than controls (p <or= 0.003). TC practitioners also spent significantly longer time in single leg support while crossing the obstacle (p < 0.001). The deleterious effect of this typically risky behavior may be mitigated in TC practitioners because of their comfort with single leg stance due to continual practice in this posture. It has been suggested that TC may reduce the risk of falls in older adults. Future studies will need to determine whether these observed gait behaviors are found in older adults and are related to reductions in fall risk.

Accidental Falls↗

PubMed2006

Generalizability of center of pressure measures of quiet standing.

Center of pressure (COP) measures are commonly used as indicators of balance and postural control. At present, there are no universally accepted standards in research investigating fluctuations in the COP with regard to the number of trials or the length of a given trial. The purpose of this study was to use the tools of Generalizability Theory (G-Theory) to investigate the reliability of COP measures of quiet standing and to establish an optimal measurement protocol. G-Theory provides a tool that allows us to break down the sources of variation, or facets, in a measurement procedure and ultimately design a protocol that provides optimal reliability. Fifteen participants completed 10 90-s trials with eyes open and closed. COP measures of anterior-posterior standard deviation (SD(AP)), medial-lateral SD (SD(ML)), average velocity (Vel), and 95% confidence ellipse area (Area) were calculated using the first 30, 60, and 90s of each trial. A G-study and follow-up D-studies were performed to estimate reliability coefficients (G-coefficients). The results of the G-Theory analysis suggest that these COP measures reached acceptable levels of reliability (G>or=0.70) with at least five 60s trials.

Adult↗

PubMed2005

Postural and eye-blink indices of the defensive startle reflex.

Postural and eye-blink reactions to acoustic startle probes were examined in 24 volunteers, who completed two blocked conditions (baseline, startle). A postural reaction during the startle condition demonstrated a reflexive movement in the anterior-posterior direction, which was not observed during the baseline condition. This reflexive response was positively associated with the eye-blink reflex, such that larger blink magnitude related to greater posterior movement. These findings were not observed for postural movements in the medial-lateral direction. The results suggest that a measurable postural reaction may be observed following a startling acoustic stimulus, which may reflect generalized bodily flexion associated with a preparatory behavioral response.

Acoustic Stimulation↗

PubMed2003

Predicting the dynamic postural control response from quiet-stance behavior in elderly adults.

Human postural sway, as measured by fluctuations of the center of pressure (COP) under the feet of a quietly standing individual, can be characterized as a stochastic process. The fluctuation-dissipation theorem (FDT) provides a linear relationship between the fluctuations of a quasi-static, stochastic system to the same system's relaxation to equilibrium following a perturbation. We applied a similar linear relationship, based on the FDT, to the human postural control system to explore whether anterior-posterior (AP) fluctuations of the COP during quiet stance can be used to predict the AP response of the postural control system to a weak posteriorly directed mechanical perturbation (tug or pull at the waist). We tested 10 healthy elderly (mean age of 69yr) and 10 healthy young (mean age of 25yr) adult subjects. We found that this linear relationship was applicable to the postural control system of all 10 young and eight of the 10 elderly adult subjects. These results suggest that it is possible to predict an individual's dynamic response to a mild perturbation using quiet-stance data, regardless of age. The existence of this FDT-based linear relationship with respect to the human postural control system suggests that, for a given individual, the postural control system may use the same control mechanisms during quiet stance and mild-perturbation conditions, regardless of age.

Adult↗