The Effect of Stirrup Length on Impact Attenuation and Its Association With Muscle Strength.

ABSTRACT: Keener, MM, Critchley, ML, Layer, JS, Johnson, EC, Barrett, SF, and Dai, B. The effect of stirrup length on impact attenuation and its association with muscle strength. J Strength Cond Res 35(11): 3056-3062, 2021-Horseback-riders have a high prevalence of low back injuries, which may be related to the repetitive low back impacts experienced in riding. The purposes of this study were to quantify the effect of 3 stirrup lengths and 2 riding styles on the peak acceleration experienced by the rider and the association between the peak acceleration and the rider's different elements of muscle strength. Thirteen female riders performed a sitting or rising trot at each of the 3 stirrup lengths (2-point length, mid-seat length, or dressage length), while the acceleration of the tibia, sacrum, seventh cervical vertebra (C7), and head were collected. Subjects completed a push-up, a vertical jump, and 4 core exercises to assess upper-body strength, lower-body strength, and core endurance, respectively. Peak acceleration of the sacrum, C7, and head were generally lower in the standing phase of the rising trot compared with the sitting phase of either the sitting or rising trot, particularly at the shortest stirrup length. Peak acceleration of the sacrum, C7, and head decreased as the stirrup length was shortened in the standing phase of the rising trot. Canonical correlations showed nonsignificant correlations between strength measurements and peak acceleration. Riding with more weight supported through the legs with a short stirrup length may decrease low back impacts and their associated injury risk. Technique training is likely needed to encourage riders to use lower-body and core strength for impact attenuation.

Kinetic Analysis of Isometric Back Squats and Isometric Belt Squats.

Layer, JS, Grenz, C, Hinshaw, TJ, Smith, DT, Barrett, SF, and Dai, B. Kinetic analysis of isometric back squats and isometric belt squats. J Strength Cond Res 32(12): 3301-3309, 2018-Belt squats seem to provide an alternative to back squats. However, it is not clear how musculoskeletal loading differs between the two. This study compared lower extremity and low-back kinetics during isometric back squats and isometric belt squats. Sixteen men (age: 22.6 ± 3.4 years; height: 1.74 ± 0.11 m; mass: 82.0 ± 5.6 kg) and 10 women (age: 21.5 ± 2.5 years; height: 1.64 ± 0.10 m; mass: 68.9 ± 7.1 kg) performed isometric back squats and belt squats at 4 squat depths. Joint resultant moments were calculated from kinematic and ground reaction force data. Linear interpolation was used to estimate peak vertical forces and joint moments at a 45° thigh segment angle. Subjects increased peak forces, ankle moments, and knee moments but decreased low-back moments from back to belt squats (p ≤ 0.023). Hip moments did not significantly change between 2 squats. Subjects demonstrating smaller ankle and knee moments during back squats showed greater increases in these moments from back to belt squats (p ≤ 0.012, R ≤ 0.24). Subjects whose back squats were characterized by greater low-back moments displayed greater decreases in low-back moments from back to belt squats (p < 0.001, R = 0.98). Compared with isometric back squats, isometric belt squats may provide a similar or greater external loading for the musculoskeletal system of the lower extremities while reducing external spinal loading. Belt squats may be considered by individuals with upper-body or spinal injuries and those displaying excessive external back moments.

VISUAL FEEDBACK ARRAY TO ACHIEVE REPRODUCIBLE LIMB DISPLACEMENTS AND VELOCITIES IN HUMANS.

Precise and reproducible feedback is important for studies on motor control, the adaptive responses to exercise training and the limits of human neuromuscular performance. For this purpose, a custom instrumentation array was previously developed to provide human subjects with visual feedback on their contractile durations and limb velocities during knee extension exercise. The array consisted of two columns, each with 14 high-visibility light emitting diodes. One array column provided the subject with the target cadence of position change while the complementary array provided an indication of the actual rate of displacement achieved by the subject. The array design has been improved to include an onboard microcontroller-based signal generator to generate the desired protocol cadence and also the ability to easily customize and 'lock in' desired protocol parameters. The array allows for custom settings to provide feedback on the concentric and eccentric activation periods during exercise. It can also be used in clinical settings to track the active or passive ranges of motion during rehabilitation.

Localization of a moving target using a fly eye sensor.

An optical sensor based on the visual system of the common housefly (Musca domestica) has been developed by the researchers at the Wyoming Image and Signal Processing Research (WISPR) Laboratory. This optical sensor shows promising peformance for detection of an edge in real-time, with minimal processing overhead. An application of this sensor might be the deflection measurement of a moving target, such as the wing of an aircraft under test. In this paper, we have investiaged the possibility of localizing an edge, and hence the target, using the fly eye sensor, which is an important part of the deflection measurement process. A simulation program has been developed for this purpose, which simulates the sensor output, for a moving object on the target plane at a specified distance from the sensor. After successfully simulating the sensor output, it has been found that the location of an edge changes with the change in sensor to target distance, and their relative orientation. It also changes for the limited movement of the target, withing the field of view (FOV) of the sensor. On the contrary, the target-background contrast scenario, and shifting of the target normal to the target movement direction, do not affect the edge localization process. This paper shows and edge can be precisely detected for a target a aspecified distance from the sensor with proper sensor-target orientation, when the target moves all the way across the FOV of the sensor.

Effect of sensor-target-background distance on target tracking using a fly eye sensor.

A multi-aperture optical sensor, known as a fly eye sensor, has been developed at the Wyoming Image and Signal Processing Research (WISPR) Laboratory based on the visual system of the common housefly Musca domestical. This biomimetic sensor shows promising edge detection capability, in varying contrast scenarios, with minimal processing overhead. Use of this sensor for fast motion detection, and object tracking is appealing, but optimizing the use of such a sensor requires detailed study. This paper analyzes the effect of placing the background at various distances greater than the target, and provides visualization of these example scenarios. A computer simulationof the sensor using MATLAB demonstrates that the placdementof a target closer to the sensor, and further from the background, affects the sensor response. If not properly considered, this may introduce ambiguities and degrade the performance of a tracking system based ont he flye eye sensor that requires precise location of the target in front of the sensor. This paper shows how a peroperly designed low-pass filter can greatly mitigate this effect with only a small degradation of the relative response magnitude at different distances from the sensor.

Results of target tracking with a Musca domestica inspired sensor.

As a follow-up to previous work done at the University of Wyoming (and presented at a previous Rocky Mountain Bioengineering Symposium), this paper discusses the results of using a Musca domestica based sensor platform as a target tracking mechanism for the measurement of wing deflection of fixed-wing aircraft. The testing of the sensor hardware and accompanying software is described, and the results are analyzed. Work remains to be done to improve robustness and adaptability, but given specific operating conditions, the sensor is a viable alternative to other technologies, and provides results with improved efficiency, speed, and computational load.

Changes, adaptations, and applications of a bio inspired machine vision sensor - biomed 2013.

The Musca domestica (common housefly) biomimetic sensor project is an ongoing endeavor at the University of Wyoming. The project has developed a sensor platform based on the rudimentary function of a fly’s compound eye, including the inherent hyperacuity (high sensitivity to motion) present in the insect’s vision. The design portion of the project is nearing completion, and application driven characterization can now begin. NASA is funding research into utilizing the sensor for efficient, fast, and inexpensive target tracking applications. This stage of the project is very preliminary, but is advancing and offers unique challenges and opportunities. his paper provides background information on the sensor design being considered, discusses the advances in the most current sensor platform, and offers an application currently being investigated.

Mapping and navigational control for a “smart” wheelchair.

A “smart” wheelchair is in development to provide mobility to those unable to control a traditional wheelchair. A “smart” wheelchair is an autonomous machine with the ability to navigate a mapped environment while avoiding obstacles. The flexibility and complex design of “smart” wheelchairs have made those currently available expensive. Ongoing research at the University of Wyoming has been aimed at designing a cheaper, alternative control system that could be interfaced with a typical powered wheelchair. The goal of this project is to determine methods for mapping and navigational control for the wheelchair. The control system acquires data from eighteen sensors and uses the data to navigate around a pre-programmed map which is stored on a micro SD card. The control system also provides a user interface in the form of a touchscreen LCD. The designed system will be an easy-to-use and cost effective alternative to current “smart” wheelchair technology.

Development of an alternative to mechanical shaft encoders for a “smart” wheelchair.

One device that is receiving a considerable amount of attention in the biomedical community is the “smart” wheelchair. “Smart” wheelchairs provide those who are unable to control the traditional joystick of a powered wheelchair with an alternative option. With minimal user input, these wheelchairs are able to autonomously navigate around a person’s environment, providing them with a higher level of mobility. The limited competition and extreme complexity of these wheelchairs propels their price outside of the affordable range for the average household. An alternative, cheaper system that could be attached to a typical powered wheelchair would be beneficial to the community.

Signal artifacts in a light-adapted, Musca domestica-based sensor system - biomed 2011.

The Musca domestica (common housefly) sensor project is an ongoing endeavor at the University of Wyoming. The project seeks to develop a sensor based on the rudimentary function of a fly’s eye, including the inherent hyperacuity (high sensitivity to motion) present in the insect’s vision. During the summer of 2010, several characterization tests were conducted on the latest sensor design at the University of Wyoming. It was found that the light-adaptation circuitry being utilized caused artifacts in the output signals. These artifacts, while initially bothersome, have a distinct use as a means to detect motion direction across the sensor’s field-of-view. This paper provides background information on the sensor design being considered, discusses one of the tests conducted, and offers results that illustrate the signal artifacts. The potential uses of these artifacts, as well as what causes them, is discussed in detail.

Preliminary tests of a possible outdoor light adaptation solution for a fly inspired visual sensor: a biomimetic solution - biomed 2011.

Two previous papers, presented at RMBS in 2009 and 2010, introduced a fly inspired vision sensor that could adapt to indoor light conditions by mimicking the light adaptation process of the commonhousefly, Muscadomestica. A new system has been designed that should allow the sensor to adapt to outdoor light conditions which will enable the sensor’s use inapplications such as: unmanned aerial vehicle (UAV) obstacle avoidance, UAV landing support, target tracking, wheelchair guidance, large structure monitoring, and many other outdoor applications. A sensor of this type is especially suited for these applications due to features of hyperacuity (or an ability to achieve movement resolution beyond the theoretical limit), extreme sensitivity to motion, and (through software simulation) image edge extraction, motion detection, and orientation and location of a line.Many of these qualities are beyond the ability of traditional computervision sensors such as charge coupled device (CCD) arrays.To achieve outdoor light adaptation, a variety of design obstacles have to be overcome such as infrared interference, dynamic range expansion, and light saturation. The newly designed system overcomes the latter two design obstacles by mimicking the fly’s solution of logarithmic compression followed by removal of the average background light intensity. This paper presents the new design and the preliminary tests that were conducted to determine its effectiveness.

Improved motion detection method using spot localization - biomed 2011.

The common house fly may be able to process certain features of images much faster than that of typical human vision. A computer model as well as a hardware model has been developed to simulate parts of the fly eye. One particular area of study in the software model has been motion detection. A new method is being developed that focuses on spot localization before motion detection. Models have been developed that can localize a spot in cylindrical coordinates with respect to the center receptor. Relative motion can be detected by analyzing the changes in the location of the spots. The advantage of this method is that it requires almost no memory. By reducing the memory required, faster frame rates can be achieved. Motion detection and spot localization will serve as the foundation for additional processing for segmentation and object recognition.

Fly eye based sensor model and animation using matlab - biomed 2011.

A new optical sensor based on the common house fly, Musca domestica, has been under development for some time at the University of Wyoming. Each sensor consists of a series of photodiodes with overlapping Gaussian field of views. The photodiodes share a common facet lens. This type of sensor provides higher movement detection and resolution than can be obtained in current charged-couple detector (CCD) arrays that are commonly used in digital imaging systems. The purpose of this research is to aid in the application and development of the fly based sensor by creating a MATLAB simulation tool to model and study the response signals from various input stimuli. In particular, the sensor detection capability and limits for line, edge and pulse stimuli will be modeled, and analyzed. Increased knowledge of the detection characteristics and limits of this type of sensor will provide insight and guidance to determine possible sensor applications. The signal analysis makes use of the Gaussian profiles that are created in MATLAB. A user-selectable input signal can be applied, while observing the output signal. The information is animated, and plotted for study and analysis. This interactive MATLAB model is a powerful tool to help understand the complex interactions of the optical signals. This sensor configuration has a variety of applications in wheelchair odometry, power line detection by unmanned aerial systems (AES), high speed railroad line inspection, and remote building monitoring.

Musca domestica based machine vision sensor: a continuing project - biomed 2010.

The Musca domestica (common housefly) sensor project is an ongoing endeavor at the University of Wyoming. The project seeks to develop a sensor based on the rudimentary function of a flys eye, including the inherent hyperacuity (high sensitivity to motion) present in the insects vision system. The primary author participated in a Wyoming Undergraduate Experimental Program to Stimulate Competitive Research (EPSCoR) summer research program in 2009. He assisted other members of the research team and conducted independent research. Specifically, he designed light filter circuits, laid out complex circuit boards, developed tests for a new sensor design, practiced new design techniques, and developed hardware to aid in future testing. His involvement in the project expedited numerous processes vital to the projects ongoing success. Notably, he aided in the design and tested a newer, simpler sensor that implemented an unprecedented light filtering technology. He then designed and executed a number of tests on that sensor. This paper describes research accomplishments contributed through his EPSCoR summer research experience.

Instrumentation array for biomechanical reproducibility - biomed 2010.

The University of Wyomings Biomechanics Laboratory is examining the link between the energetics and mechanics of both human and animal locomotion. The group is currently investigating how there lative duration of muscular activity (i.e. duty factor) influences the time course of performance loss resulting from the impairment in muscle force production that occurs as the duration of an all-out or text ends from seconds to minutes. In order to conduct one of their experimental protocols, this group requires human subjects to precisely and repeatedly match prescribed contractile and relaxation periods during knee-extension exercise. To provide subjects with visual feedback with respect to their adherence to the assigned contractile durations and limb velocities, a custom instrumentation array panel was developed consisting of two arrays of high-visibility light emitting diodes. One array provides the experimental subject with the selected, or target, rate of position change while the complementary array provides an indication of the actual rate of displacement achieved by the subject.

Three-dimensional rendering of segmented object using matlab - biomed 2010.

The three-dimensional rendering of microscopic objects is a difficult and challenging task that often requires specialized image processing techniques. Previous work has been described of a semi-automatic segmentation process of fluorescently stained neurons collected as a sequence of slice images with a confocal laser scanning microscope. Once properly segmented, each individual object can be rendered and studied as a three-dimensional virtual object. This paper describes the work associated with the design and development of Matlab files to create three-dimensional images from the segmented object data previously mentioned. Part of the motivation for this work is to integrate both the segmentation and rendering processes into one software application, providing a seamless transition from the segmentation tasks to the rendering and visualization tasks. Previously these tasks were accomplished on two different computer systems, windows and Linux. This transition basically limits the usefulness of the segmentation and rendering applications to those who have both computer systems readily available. The focus of this work is to create custom Matlab image processing algorithms for object rendering and visualization, and merge these capabilities to the Matlab files that were developed especially for the image segmentation task. The completed Matlab application will contain both the segmentation and rendering processes in a single graphical user interface, or GUI. This process for rendering three-dimensional images in Matlab requires that a sequence of two-dimensional binary images, representing a cross-sectional slice of the object, be reassembled in a 3D space, and covered with a surface. Additional segmented objects can be rendered in the same 3D space. The surface properties of each object can be varied by the user to aid in the study and analysis of the objects. This inter-active process becomes a powerful visual tool to study and understand microscopic objects.

Graphical user interface to optimize image contrast parameters used in object segmentation - biomed 2009.

Image segmentation is the process of isolating distinct objects within an image. Computer algorithms have been developed to aid in the process of object segmentation, but a completely autonomous segmentation algorithm has yet to be developed [1]. This is because computers do not have the capability to understand images and recognize complex objects within the image. However, computer segmentation methods [2], requiring user input, have been developed to quickly segment objects in serial sectioned images, such as magnetic resonance images (MRI) and confocal laser scanning microscope (CLSM) images. In these cases, the segmentation process becomes a powerful tool in visualizing the 3D nature of an object. The user input is an important part of improving the performance of many segmentation methods. A double threshold segmentation method has been investigated [3] to separate objects in gray scaled images, where the gray level of the object is among the gray levels of the background. In order to best determine the threshold values for this segmentation method the image must be manipulated for optimal contrast. The same is true of other segmentation and edge detection methods as well. Typically, the better the image contrast, the better the segmentation results. This paper describes a graphical user interface (GUI) that allows the user to easily change image contrast parameters that will optimize the performance of subsequent object segmentation. This approach makes use of the fact that the human brain is extremely effective in object recognition and understanding. The GUI provides the user with the ability to define the gray scale range of the object of interest. These lower and upper bounds of this range are used in a histogram stretching process to improve image contrast. Also, the user can interactively modify the gamma correction factor that provides a non-linear distribution of gray scale values, while observing the corresponding changes to the image. This interactive approach gives the user the power to make optimal choices in the contrast enhancement parameters.

Software model of an improved bio-inspired sensor - biomed 2009.

Researchers at the Wyoming Information, Signal Processing, and Robotics (WISPR) Laboratories are developing a bio-inspired sensor based on the visual system of the common house degrees y (Musca domestica). The degrees y's visual system has many bene cial characteristics which we seek to replicate. Most notably, degrees ies exhibit motion hyperacuity (i.e., they are able to detect motion much smaller than their photoreceptor spacing suggests). Recent research has shown that this is due to a pre-blurring of the image which results in overlapping Gaussian responses in the photoreceptors. Current biomimetic sensors developed at the WISPR Labs utilize this concept of pre-blurring and have been shown to exhibit hyperacuity. However, this hyperacuity comes at the expense of individual photodetector responses. We have modeled a new sensor that more closely resembles the Musca domestica. It pools responses from multiple lenses rather than a single lens. This allows for increased photodetector responses, adjustable response shape and overlap, and improved motion detection. In this paper we report the results of a software model developed with Zemax optical design software. We show how the model allows us to optimize the shape, magnitude, and overlap of the photodetector responses. Finally, we describe how the optimization is beneficial in the context of hyperacuity.

The design of an analog module for sensor adaptation to changes in ambient light: a bio-inspired solution - biomed 2009.

Fly inspired vision sensors have been shown to have many interesting qualities such as hyperacuity (or an ability to achieve movement resolution beyond the theoretical limit), extreme sensitivity to motion, and (through software simulation) image edge extraction, motion detection, and orientation and location of a line. Many of these qualities are beyond the ability of traditional computer vision sensors such as charge-coupled device (CCD) arrays. To obtain these characteristics, a prototype fly inspired sensor has been built and tested in a laboratory environment and shows promise. Any sophisticated visual system, whether man made or natural, must adequately adapt to lighting conditions, therefore light adaptation is a vital milestone in getting the afore mentioned prototype working in real-world conditions. By studying how the common house fly, Musca domestica, achieves this adaptation it was possible to design an analog solution to this problem. The solution utilizes instrumentation amplifiers and an additional sensor to sense the ambient light. This paper will examine this circuitry in greater detail and will explore the characterization and limitations of this solution.

Computer-assisted laser tattoo removal: a proposed prototype system - biomed 2009.

It is estimated that there are 7-20 million tattooed people in the United States. This number will probably grow as evidenced by reported increases in the number of tattoo studios and the sales of tattoo related supplies. Consistent with this growth in tattoo placement is anticipated increase in the demand for tattoo removals. Studies by Armstrong et al. indicate that many people want to have tattoos removed. Most participants in the studies indicated they had "impulsively obtained their tattoos for internal expectations of self-identity at an early age and were still internally motivated to dissociate from the past and improve self-identity [1]." Currently there are several lasers approved for tattoo removal: the Q-switched ruby (694 nm), the Q-switched Nd:YAG (532 nm, 1064 nm) and Nd:YAG pumped dye lasers at 585 nm and 650 nm.. A technique called Selective Photothermolysis is used to remove the tattoos. The goal of this project was to investigate the feasibility of a computer-assisted laser tattoo removal system to limit damage to collateral areas and scarring while significantly reducing the length and the number of treatment sessions. This was accomplished by characterizing the absorption properties of common tattoo inks, reviewing the limitations of current laser tattoo removal systems, and proposing a prototype system configuration.