Sensory-Related Changes in Two-Segment Dynamics on a Sway-Referenced Support Surface

In its simplest form, the human postural control system can be described as a closed-loop control system consisting of a plant (body segments and musculotendon actuators) and feedback. Previous efforts to understand the contributions of plant and feedback employed techniques to "open the loop" which is problematic with the study of posture because the plant is unstable without feedback. In the present experiment, a closed-loop system identification method was used to "open the loop" without removal of sensory feedback. Subjects stood on a movable platform facing a visual scene, both of which were capable of rotation about an axis coaxial with the subject's ankles. The visual stimulus (present all trials) consisted of a 10-frequency sum-of-sines while movement of the support surface consisted of the following conditions: 1. Stationary; 2. Sway-referenced to the subject's body sway; 3. 10-frequency sum-of-sines; 4. Combined sway-referenced and sum-of-sines. Closed-loop frequency response functions were calculated for visual stimulus to EMG and visual stimulus to body sway angle. The open loop frequency response function for the plant was determined by dividing the frequency response functions, mathematically canceling the effects of feedback. With respect to the visual stimulus, gains for the leg segment showed no differences between the four platform conditions. Phase for the stationary condition was lower at the higher stimulus driving frequencies than for any of the moving platform conditions. In contrast, trunk segment gains were lower for the sway-referenced conditions at lower stimulus frequencies than for the stationary and sum-of-sines conditions. Phase showed a slight lead of the legs over the trunk for the sway-referenced conditions. The phase relationship between the trunk and leg segments, typically in-phase below ~1 Hz and anti-phase above ~1 Hz, showed a gradual transition at a lower frequency for the sway-referenced conditions than for the stationary or sum-of-sines conditions. Complex coherence showed a "legs-leading" coordinative relationship at the phase mode transition for the two sway-referenced conditions. Differences in the frequency response functions demonstrate that the plant changes with platform condition requiring different postural control strategies to maintain stability

Posture and Locomotion Coupling: A Target for Rehabilitation Interventions in Persons with Parkinson's Disease

Disorders of posture, balance, and gait are debilitating motor manifestations of advancing Parkinson's disease requiring rehabilitation intervention. These problems often reflect difficulties with coupling or sequencing posture and locomotion during complex whole body movements linked with falls. Considerable progress has been made with demonstrating the effectiveness of exercise interventions for individuals with Parkinson's disease. However, gaps remain in the evidence base for specific interventions and the optimal content of exercise interventions. Using a conceptual theoretical framework and experimental findings, this perspective and review advances the viewpoint that rehabilitation interventions focused on separate or isolated components of posture, balance, or gait may limit the effectiveness of current clinical practices. It is argued that treatment effectiveness may be improved by directly targeting posture and locomotion coupling problems as causal factors contributing to balance and gait dysfunction. This approach may help advance current clinical practice and improve outcomes in rehabilitation for persons with Parkinson's disease

Noise and response characterization of a HgCdTe photoconductive detection system

Thesis (M.S.)--University of Rochester. College of Engineering and Applied Science. Institute of Optics, 1981. This thesis was digitized by the Institute of Optics in 2014 and was determined to have lapsed into the public domain. If you are the author and have questions about the digitization of your work, please contact Kari Brick, Graduate Program Coordinator for the Institute of Optics, at [email protected]. Other contact information for the Institute is available at http://www.optics.rochester.eduIt was found that the responsivity and detector noise of a Hg₀.₈Cd₀.₂Te photoconductive detection system show deviations from linearity at large flux levels. Laboratory measurements of detector characteristics are interpreted using physical models developed to describe the photoconductive process. Response measurements show that at low flux levels the detector conductance increases linearly with the incident photon rate, but at high photon fluxes, the response falls off to become proportional to the square root of the photon rate. This effect is due to a carrier lifetime that changes with the incident flux. In the small signal limit, the carrier lifetime is nearly constant, but at high photon fluxes, it rapidly decreases because of donor impurities which affect the recombination processes present in the detector. Interpretation of the noise measurements shows that the generation-recombination process constitutes the predominant noise source in this detection-system. The system is found to be background limited, and the conductance fluctuations increase linearly with the photon rate at low flux levels, and then saturate in the limit of high flux levels. This behavior is in agreement with the change of conductance with photon flux level. Noise measurements made with large detector bias currents show that the model predicts more noise than is actually present in this limit. This suggests that the standard, simple model of generation-recombination noise presented in this thesis is not adequate to treat the noise characteristics under high-background conditions

A method for simulating forward falls and controlling impact velocity

Assessment of protective arm reactions associated with forward falls are typically performed by dropping research participants from a height onto a landing surface. The impact velocity is generally modulated by controlling the total height of the fall. This contrasts with an actual fall where the fall velocity is dependent on several factors in addition to fall height and not likely predictable at the onset of the fall. A counterweight and pulley system can be used to modulate the fall velocity in simulated forward falls in a manner that is not predictable to study participants, enhancing experimental validity. However, predicting the fall velocity based on participant height and weight and counterweight mass is not straightforward. In this article, the design of the FALL simulator For Injury prevention Training and assessment (FALL FIT) system is described. A dynamic model of the FALL FIT and counterweight system is developed and model parameters are fit using nonlinear optimization and experimental data. The fitted model enables prediction of fall velocity as a function of participant height and weight and counterweight load. The method can be used to provide controllable perturbations thereby elucidating the control strategy used when protecting the body from injury in a forward fall, how the control strategy changes because of aging or dysfunction or as a method for progressive protective arm reaction training. • Construction of device to simulate forward falls with controllable impact velocity using material that are commercially available is described • A dynamic model of the FALL FIT is developed to estimate the impact velocity of a simulated forward fall using participant height and counterweight load • The dynamic model is validated using data from 3 previous studie

Relationship Between Allied Health Student\u27s Behavioral Style and Ideal Clinical Instructor Behaviors

Purpose: The focus of this research is to understand the relationship between students\u27 primary DISC behavioral styles (dominant, influencing, steadiness, compliance) and their perception of ideal clinical instructor behaviors. A review of the literature supports the connection between the behaviors of the clinical instructor (CI) and the success of the allied health professional student (AHPS). Additionally, a body of research supports the connection between DISC behavioral styles and student success. The purpose of this study is to examine the relationship between AHPS primary DISC behavioral styles and their perception of the ideal CI behaviors. Methods: A total number of n=90 participants completed the Allied Health Professional Preceptor Assessment exploring ideal CI behaviors and the DISC assessment across the three disciplines of athletic training (14), exercises science (7), and physical therapy (69). Results: S (steadiness) scores had the highest frequency (53.3%), followed by I (influencing) (22.2%), then C (compliance) (13.3.7%), and lastly, D (dominant) (11.1%). Using regression modeling, the D model (p=0.01) and the S model (pConclusion:This study provides preliminary evidence for the DISC behavioral assessment as a tool to inform CIs in ways to engage AHPS effectively. The findings of this study provide applicable techniques for CIs mentoring students with D, S, and C primary behavioral styles. Further research is warranted to determine engagement strategies for I primary behavioral styles. By leveraging these findings, clinical education programs can provide CIs with simple behavioral techniques to best engage students based on the student\u27s primary behavioral style

Influence of Bilateral Vestibular Loss on Spinal Stabilization in Humans

The control of upper body (UB) orientation relative to the pelvis in the frontal plane was characterized in bilateral vestibular loss subjects (BVLs) and compared with healthy control subjects (Cs). UB responses to external perturbations were evoked using continuous pelvis tilts (eyes open and eyes closed) at various amplitudes. Lateral sway of the lower body was prevented on all tests. UB sway was summarized using root-mean-square measures and dynamic behavior was characterized using frequency response functions (FRFs) from 0.023 to 10.3 Hz. Both subject groups had similar FRF variations as a function of stimulus frequency and were relatively unaffected by visual availability, indicating that visual orientation cues contributed very little to UB control. BVLs had larger UB sway at frequencies below ∼1 Hz compared with Cs. A feedback model of UB orientation control was used to identify sensory contributions to spinal stability and differences between subject groups. The model-based interpretation of experimental results indicated that a phasic proprioceptive signal encoding the angular velocity of UB relative to lower body motion was a major contributor to overall system damping. Parametric system identification showed that BVLs used proprioceptive information that oriented the UB toward the pelvis to a greater extent compared with Cs. Both subject groups used sensory information that oriented the UB vertical in space to a greater extent as pelvis tilt amplitudes increased. In BVLs, proprioceptive information signaling the UB orientation relative to the fixed lower body provided the vertical reference, whereas in Cs, vestibular information also contributed to the vertical reference

FabAV antivenin use after copperhead snakebite: clinically indicated or knee-jerk reaction?

Abstract Background Crotalidae Polyvalent Immune Fab (Ovine) (FabAV) antivenin is commonly recommended after pit viper snakebites. Because copperhead envenomations are usually self-limited, some physicians are reluctant to use this costly treatment routinely, while others follow a more liberal approach. We hypothesized that, in practice, only patients with evidence of significant (moderate or severe) copperhead envenomation [those with snakebite severity score (SSS) > 3] receive FabAV and examined a large cohort to determine the relationship between clinical findings and FabAV administration. Methods All data from patients evaluated for copperhead snakebite at a rural tertiary referral center from 5/2002 to 10/2013 were compiled. Demographics, transfer status, antivenin use, and clinical findings were collected; SSS was calculated. The relationships among FabAV use, clinical findings, and SSS were analyzed using t-test, chi-square, and Pearson’s coefficient (p 3, indicating moderate or severe envenomation, was only very weakly correlated with antivenin use (r = 0.217;p 3 (65.8 %) did not receive antivenin while most patients who did receive antivenin (70.5 %) had SSS ≤ 3 (indicating mild envenomation). Conclusions Considerable variation occurs in antivenin administration after copperhead snakebite. Use of FabAV appears poorly correlated with patients’ symptoms. This practice may expose patients to the risks of antivenin and increasing costs of medical care without improving outcomes. Guidelines used for treating other pit viper strikes, such as rattlesnake or cottonmouth snakebite may be too liberal for copperhead envenomations. Our data suggests that most patients with mild or moderate envenomation appear to do well independent of FabAV use. We suggest, for patients with copperhead snakebite, that consideration be given to withholding FabAV for those without clinical evidence of severe envenomation until prospective randomized data are available

Micro-doppler radar to evaluate risk for musculoskeletal injury: Protocol for a case-control study with gold standard comparison.

BackgroundBeyond causing significant morbidity and cost, musculoskeletal injuries (MSKI) are among the most common reasons for primary care visits. A validated injury risk assessment tool for MSKI is conspicuously absent from current care. While motion capture (MC) systems are the current gold standard for assessing human motion, their disadvantages include large size, non-portability, high cost, and limited spatial resolution. As an alternative we introduce the Micro Doppler Radar (MDR); in contrast with MC, it is small, portable, inexpensive, and has superior spatial resolution capabilities. While Phase 1 testing has confirmed that MDR can identify individuals at high risk for MSKI, Phase 2 testing is still needed. Our aims are to 1) Use MDR technology and MC to identify individuals at high-risk for MSKI 2) Evaluate whether MDR has diagnostic accuracy superior to MC 3) Develop MDR algorithms that enhance accuracy and enable automation.Methods and findingsA case control study will compare the movement patterns of 125 ACL reconstruction patients to 125 healthy controls. This study was reviewed and approved by the Pennsylvania State University Human Research Protection Program (HRPP) on May 18, 2022, and the IRB approval number is STUDY00020118. The ACL group is used as a model for a "high risk" population as up to 24% will have a repeat surgery within 2 years. An 8-camera Motion Analysis MC system with Cortex 8 software to collect MC data. Components for the radar technology will be purchased, assembled, and packaged. A micro-doppler signature projection algorithm will determine correct classification of ACL versus healthy control. Our previously tested algorithm for processing the MDR data will be used to identify the two groups. Discrimination, sensitivity and specificity will be calculated to compare the accuracy of MDR to MC in identifying the two groups.ConclusionsWe describe the rationale and methodology of a case-control study using novel MDR technology to detect individuals at high-risk for MSKI. We expect this novel approach to exhibit superior accuracy than the current gold standard. Future translational studies will determine utility in the context of clinical primary care

A comparison of initial lactate and initial base deficit as predictors of mortality after severe blunt trauma

After injury, base deficit (BD) and lactate are common measures of shock. Lactate directly measures anaerobic byproducts, whereas BD is calculated and multifactorial. Although recent studies suggest superiority for lactate in predicting mortality, most were small or analyzed populations with heterogeneous injury severity. Our objective was to compare initial BD with lactate as predictors of inhospital mortality in a large cohort of blunt trauma patients all presenting with hemorrhagic shock. The Glue Grant multicenter prospective cohort database was queried; demographic, injury, and physiologic parameters were compiled. Survivors, early deaths (≤24 h), and late deaths were compared. Profound shock (lactate ≥ 4 mmol/L) and severe traumatic brain injury subgroups were identified a priori. Chi-square, t-test, and analysis of variance were used as appropriate for analysis. Multivariable logistic regression and area under the receiver operating characteristic curve analysis assessed survival predictors. P < 0.05 was significant. A total of 1829 patients met inclusion; 289 (15.8%) died. Both BD and lactate were higher for nonsurvivors (P < 0.00001). After multivariable regression, both lactate (odds ratio [OR] 1.17; 95% confidence interval [CI]: 1.12-1.23; P < 0.00001) and BD (OR 1.04; 95% CI: 1.01-1.07; P < 0.005) predicted overall mortality. However, when excluding early deaths (n = 77), only lactate (OR 1.12 95% CI: 1.06-1.19; P < 0.0001) remained predictive but not BD (OR 1.00 95% CI: 0.97-1.04; P = 0.89). For the shock subgroup, (n = 915), results were similar with lactate, but not BD, predicting both early and late deaths. Findings also appear independent of traumatic brain injury severity. After severe blunt trauma, initial lactate better predicts inhospital mortality than initial BD. Initial BD does not predict mortality for patients who survive >24 h