Stick balancing at the fingertip is a powerful paradigm for the study of the control of human balance. Here we show that the mean stick balancing time is increased by about two-fold when a subject stands on a vibrating platform that produces vertical vibrations at the fingertip (0.001 m, 15–50 Hz). High speed motion capture measurements in three dimensions demonstrate that vibration does not shorten the neural latency for stick balancing or change the distribution of the changes in speed made by the fingertip during stick balancing, but does decrease the amplitude of the fluctuations in the relative positions of the fingertip and the tip of the stick in the horizontal plane, A(x,y). The findings are interpreted in terms of a time-delayed “drift and act” control mechanism in which controlling movements are made only when controlled variables exceed a threshold, i.e. the stick survival time measures the time to cross a threshold. The amplitude of the oscillations produced by this mechanism can be decreased by parametric excitation. It is shown that a plot of the logarithm of the vibration-induced increase in stick balancing skill, a measure of the mean first passage time, versus the standard deviation of the A(x,y) fluctuations, a measure of the distance to the threshold, is linear as expected for the times to cross a threshold in a stochastic dynamical system. These observations suggest that the balanced state represents a complex time–dependent state which is situated in a basin of attraction that is of the same order of size. The fact that vibration amplitude can benefit balance control raises the possibility of minimizing risk of falling through appropriate changes in the design of footwear and roughness of the walking surfaces.

After lower extremity fracture or surgery, physicians often prescribe limited weight bearing. The current study was performed to evaluate teaching and compliance of touch-down weight bearing (defined as 25 lb) at a level I academic trauma center. A survey was distributed to physical therapists (PTs) from the orthopedic ward to gauge their training methods and their confidence in patients' ability to comply. Patients with recommended touch-down weight bearing were then evaluated on the day of discharge and again at their first follow-up appointment using the SmartStep weight-bearing measurement device (Andante Medical Devices, Inc, White Plains, New York). Fifteen PTs completed the survey (average of 14 years in practice). Inconsistency was observed in weight-bearing teaching methods: verbal cues were used 87% of the time, tactile methods were used 41%, demonstration was used 23%, and a scale was used only 1%. Limited confidence was found in the instruction efficacy by those surveyed. Twenty-one patients were seen the day of discharge and 18 of those were seen at first follow-up. At discharge, average minimum and maximum weight bearing were 3.2 and 30.2 lb, respectively. Only 31% of steps were within an acceptable range of 15 to 35 lb. At first follow-up, average minimum and maximum weight bearing were 12.2 and 50.8 lb, respectively. Only 27% of steps were within the acceptable range. The majority of steps were less than the prescribed weight at discharge, whereas the majority of steps were greater than the prescribed weight at first follow-up. These data suggest that more uniform and effective teaching methods for prescribed weight-bearing orders are warranted assuming compliance is an important clinical objective.

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We demonstrate that a genetic test correlates with bracing outcome. It may be appropriate for future bracing studies to include analysis of genetic predisposition to limit potential confounding.

Findings highlight extreme variability in practice associated with a notable lack of standard of care and provide a baseline for utility studies that may lead to more evidence-driven care.