Timothy A. Thrasher

Smartphone based fall detection system

This paper describes the design of a smartphone based fall detection system and characterizes the preliminary efficacy of the proposed system in activities of daily living (ADLs). Using the embedded sensors available in a smartphone (i.e., accelerometer, gyroscope and magnetometer), kinematic analysis of movement can be performed in real-time, allowing for continuous monitoring of fall status. Fall sensing thresholds are defined based on angular rate of change (TH1), maximum acceleration (TH2), and maximum attitude change (TH3). TH1 is measured from the resultant pitch and roll angular velocity vector and defined as 3.1 rad/s (~180°/s). TH2 is measured from the resultant acceleration vector and defined as 1.6 g. TH3 is measured from the resultant vector of the pitch and roll angles, and defined at 0.59 rad (39°). A proof-of-concept study was performed on five ADL tasks: 1) comfortable walking, 2) stand-to-seated posture, 3) seated-to-standing posture, 4) pivoting at the waist to pick up an object, and 5) stand-to-seated-to-laying transition. No trials violated the defined thresholds for fall detection, signifying no false positives. These results are important for the definition of machine learning algorithms, currently under development, to minimize false positive and false negative fall detection events.

Strength and endurance adaptations to functional electrical stimulation leg cycle ergometry in spinal cord injury

OBJECTIVES To describe adaptations in power output, quadriceps muscle strength, and fatigability that occur during a 13-week regimen of Functional Electrical Stimulation Leg Cycle Ergometry (FES-LCE) in Spinal Cord Injury (SCI). To identify differences in outcomes between individuals with complete and incomplete motor impairment. DESIGN Observational and longitudinal. SETTING Rehabilitation and biomechanics research laboratory. PARTICIPANTS Eleven (N = 11) individuals with SCI and no previous FES-LCE experience. INTERVENTION 40 sessions of FES-LCE at a rate of three sessions per week. Continuous exercise was performed at a pedal cadence of 45 RPM against a constant resistance for up to 60 minutes. OUTCOME MEASURES Mean power output was recorded for each session. Before and after the training regimen, each subject performed a fatigue test in which electrically stimulated knee extension torque and Fatigue Index were measured. RESULTS Participants demonstrated significant increases in mean power output (9.0 to 20.3 W; p < 0.001), peak isometric knee extension torque (3.8 to 16.9 Nm; p = 0.006) and sustainable isometric knee extension torque (4.9 to 14.4 Nm; p = 0.001) after FES-LCE training (95% confidence intervals). Participants with incomplete motor impairment demonstrated a decrease in Fatigue Index (p = 0.021), and improved mean power output more than those with complete motor impairment (p = 0.037). CONCLUSIONS Significant improvements in muscle conditioning and exercise performance are possible following the 13-week regimen of FES-LCE described in this article. Individuals with incomplete motor impairment experience greater improvements in mean power output than individuals with complete motor impairment.

Societal costs of intrathecal drug delivery systems--an administrative analysis based on patient claims.

To quantify the overall and disaggregated societal costs of intrathecal drug delivery systems (IDDSs) in the treatment of pain and spasticity in the United States.

The Effect of Vibrotactile Cuing on Recovery Strategies From a Treadmill-Induced Trip

Effective fall prevention technologies need to detect and transmit the key information that will alert an individual in advance about a potential fall. This study investigated advanced vibrotactile cuing that may facilitate trip recovery for balance-impaired individuals who are prone to falling. A split-belt treadmill that simulated unpredictable trip perturbations was developed to compare balance recovery without and with cuing. Kinetic and kinematic measures from force plates and full body motion capture system were used to characterize the recovery responses. Experiment I evaluated recovery adaptation resulting from repeated trip exposure without vibrotactile cuing. Experiment II investigated the effects of vibrotactile cuing as a function of cuing location (upper arm, trunk, lower leg) and lead time prior to a trip (250, 500 ms). Experiment I showed that trip recovery improved progressively from the fourth to the eighth trial. Experiment II showed that trip recovery was almost the same as the eighth trial in Experiment I, regardless of the location of the cuing stimulus and lead time. The results suggest that a combination of vibrotactile cuing and hazard detection technology could reduce the risk of trips and falls

The Effects of Coding Schemes on Vibrotactile Biofeedback for Dynamic Balance Training in Parkinson’s Disease and Healthy Elderly Individuals

Coding scheme for earlier versions of vibrotactile biofeedback systems for balance-related applications was primarily binary in nature, either on or off at a given threshold (range of postural tilt), making it unable to convey information about error magnitude. The purpose of this paper was to explore the effects of two coding schemes (binary versus continuous) for vibrotactile biofeedback during dynamic weight-shifting exercises that are common physical therapists’ recommended balance exercises used in clinical settings. Nine individuals with idiopathic Parkinson’s disease and nine healthy elderly individuals participated in this paper. All participants performed dynamic weight-shifting exercises assisted with either the binary or continuous vibrotactile biofeedback delivered using with vibrating actuators (tactors) in either the anterior–posterior or medial–lateral direction. Participants’ limits of stability at pre and post exercises were compared to evaluate the effects of the exercises on their range of motion. The continuous coding scheme produced significantly better performance than the binary scheme when both groups were performing dynamic weight-shifting balance exercises with assistive vibrotactile biofeedback. The results have implications in terms of maximizing the effects of error-driven motor learning and increasing performance on balance rehabilitation training combined with vibrotactile biofeedback.

A new fall-inducing technology platform: Development and assessment of a programmable split-belt treadmill

Typical technologies for fall reduction/prevention training incorporate mechanical obstacles or cables/pulleys to induce trip or slip perturbations. This paper proposes a technology platform that uses a split-belt treadmill equipped with one force plate underneath each belt and a real-time gait phase detection algorithm. A proof-of-concept study validates the method for inducing trip perturbations in healthy young adults (n=10) by using kinematic measures from a full body motion capture system to characterize the effects of the perturbations. Preliminary results show that the proposed method successfully induces a trip and its congruent postural responses. The major findings have implications for designing intervention programs to reduce or prevent falls by individuals with a high risk of falls.