Michele Oliver

Determining physiological cross-sectional area of extensor carpi radialis longus and brevis as a whole and by regions using 3D computer muscle models created from digitized fiber bundle data

Architectural parameters and physiological cross-sectional area (PCSA) are important determinants of muscle function. Extensor carpi radialis longus (ECRL) and brevis (ECRB) are used in muscle transfers; however, their regional architectural differences have not been investigated. The aim of this study is to develop computational algorithms to quantify and compare architectural parameters (fiber bundle length, pennation angle, and volume) and PCSA of ECRL and ECRB. Fiber bundles distributed throughout the volume of ECRL (75+/-20) and ECRB (110+/-30) were digitized in eight formalin embalmed cadaveric specimens. The digitized data was reconstructed in Autodesk Maya with computational algorithms implemented in Python. The mean PCSA and fiber bundle length were significantly different between ECRL and ECRB (p < or = 0.05). Superficial ECRL had significantly longer fiber bundle length than the deep region, whereas the PCSA of superficial ECRB was significantly larger than the deep region. The regional quantification of architectural parameters and PCSA provides a framework for the exploration of partial tendon transfers of ECRL and ECRB.

A New Laser Reflectance System Capable of Measuring Changing Cross-Sectional Area of Soft Tissues During Tensile Testing

Determination of the biomechanical properties of soft tissues such as tendons and ligaments is dependent on the accurate measurement of their cross-sectional area (CSA). Measurement methods, which involve contact with the specimen, are problematic because soft tissues are easily deformed. Noncontact measurement methods are preferable in this regard, but may experience difficulty in dealing with the complex cross-sectional shapes and glistening surfaces seen in soft tissues. Additionally, existing CSA measurement systems are separated from the materials testing machine, resulting in the inability to measure CSA during testing. Furthermore, CSA measurements are usually made in a different orientation, and with a different preload, prior to testing. To overcome these problems, a noncontact laser reflectance system (LRS) was developed. Designed to fit in an Instron 8872 servohydraulic test machine, the system measures CSA by orbiting a laser transducer in a circular path around a soft tissue specimen held by tissue clamps. CSA measurements can be conducted before and during tensile testing. The system was validated using machined metallic specimens of various shapes and sizes, as well as different sizes of bovine tendons. The metallic specimens could be measured to within 4% accuracy, and the tendons to within an average error of 4.3%. Statistical analyses showed no significant differences between the measurements of the LRS and those of the casting method, an established measurement technique. The LRS was successfully used to measure the changing CSA of bovine tendons during uniaxial tensile testing. The LRS developed in this work represents a simple, quick, and accurate way of reconstructing complex cross-sectional profiles and calculating cross-sectional areas. In addition, the LRS represents the first system capable of automatically measuring changing CSA of soft tissues during tensile testing, facilitating the calculation of more accurate biomechanical properties.

Six-degree-of-freedom whole-body vibration exposure levels during routine skidder operations

This research focuses on quantifying six-degree-of-freedom (6-DOF) whole-body vibration (WBV) exposure levels that occur in Northern Ontario skidders during routine field operating tasks. 6-DOF vibration running root-mean-square (RMS) acceleration levels at the operator/seat interface were determined for eight skidders while driving loaded, driving unloaded, picking up a load, dropping off a load and ploughing logs under field operating conditions. The acceleration data were weighted in accordance with ISO 2631–1:1997 and evaluated for both health and comfort outcomes. The mean running RMS weighted translational and rotational accelerations all exceeded 0.36 m/s2 and 0.14 rad/s2. The greatest average accelerations occurred while driving unloaded with this condition displaying translational vibration total values (VTV) that exceeded the upper limit of the ISO 2631–1:1997 health caution zone within an average of 2.3 h. Utilizing 6-DOF VTV, virtually all operating conditions would be designated as uncomfortable. Statement of Relevance: This study provides one of the most comprehensive reports on vibration exposures in seated vehicle operators. The results are geared towards ergonomists with discussions on health effects and measurement concerns, while providing the raw vibration exposure data that will be useful to vehicle, component and vibration sensor designers.

Multi-Axis Sinusoidal Whole-Body Vibrations: Part II — Relationship between Vibration Total Value and Discomfort Varies between Vibration Axes

The influence of vibration duration and the amount of rest between successive vibrations was addressed in Part I of this study. The relationship between discomfort and Vibration Total Value for different axes of vibration is assessed in Part II. Ten subjects were exposed to repeated single axis, planar, and 6 degree of freedom multi-axial vibrations. We observed statistically significant differences in discomfort between the different axes of vibration for similar ranges of Vibration Total Values. In particular. we observed that discomfort reports for vibrations in the Z axis and XY plane were less than discomfort reports associated with XZ plane and 6 df vibrations when the same range of Vibration Total Values were compared. Furthermore, single axis vertical vibrations were typically associated with less discomfort than multi-axis vibrations when similar ranges of Vibration Total Values were compared. This finding infers that the frequency weighting scheme presented in ISO 2631–1 does not achieve inter-axis equivalence and indicates that a more comprehensive study of multi-axis vibration is required to suggest changes to the ISO 2631–1 weighting factors.

Neuromuscular partitioning in the extensor carpi radialis longus and brevis based on intramuscular nerve distribution patterns: A three-dimensional modeling study.

Differential activation of specific regions within a skeletal muscle has been linked to the presence of neuromuscular compartments. However, few studies have investigated the extra‐ or intramuscular innervation throughout the muscle volume of extensor carpi radialis longus (ECRL) and brevis (ECRB). The aim of this study was to determine the presence of neuromuscular partitions in ECRL and ECRB based on the extra‐ and intramuscular innervation using three‐dimensional modeling. The extra‐ and intramuscular nerve distribution was digitized and reconstructed in 3D in all the muscle volumes using Autodesk Maya in seven formalin embalmed cadaveric specimens (mean age, 75.7 ± 15.2 years). The intramuscular nerve distribution was modeled in all the muscle volumes. ECRL was found to have two neuromuscular compartments, superficial and deep. One branch from the radial nerve proper was found to innervate ECRL. This branch was divided into anterior and posterior branches to the superficial and deep compartments, respectively. Five innervation patterns were identified in ECRB with partitioning of the muscle belly into two, three, or four compartments, in a proximal to distal direction depending on the number of nerve branches entering the muscle belly. The ECRL and ECRB both demonstrated neuromuscular compartmentalization based on intramuscular innervation. According to the partitioning hypothesis, a muscle may be differentially activated depending on the required function of the muscle, thus allowing multifunctional muscles to contribute to a variety of movements. Therefore, the increased number of neuromuscular partitions in ECRB when compared with ECRL could be due to the need for more differential recruitment in the ECRB depending on force requirements. Clin. Anat. 25:366–372, 2012.

Multi-axis sinusoidal whole-body vibrations: Part I - How long should the vibration and rest exposures be for reliable discomfort measures?

Laboratory-based whole-body vibration studies often involve complex experimental designs, dozens of vibration exposures and multiple sessions. Shortening the test vibration duration would increase experimental efficiency by permitting more trials in the same time period. This study evaluated reported discomfort based on different sinusoidal vibration durations and amounts of rest between successive vibrations. Ten subjects were exposed to four blocks of vibration trials (15/20 second vibration and 5/10 second rest durations). Each block of 37 trials included repeated single axis, planar, and 6 degree of freedom multi-axial vibrations. These repeated trials were analysed to evaluate whether discomfort varied between the different blocks. We did not observe any statistically significant differences in discomfort between the different vibration and rest durations. This finding is useful for designing future vibration experiments. Part II of this study evaluates the relationship between discomfort and vibration exposure.

Effect of stiffness and movement speed on selected dynamic torque characteristics of hydraulic-actuation joystick controls for heavy vehicles

The purpose of this work was to quantify the effects of joystick stiffness and movement speed on the dynamic torque characteristics of hydraulic-actuation joystick controls, as found in off-road vehicles, as one of the initial steps towards the development of a joystick design protocol. Using a previously developed mathematical model in which a hydraulic-actuation joystick is assumed to rotate about two axes where the rotation origin is a universal joint, the dynamic torque characteristics incurred by an operator were predicted. Utilizing a laboratory mock-up of an excavator cab environment, three actuation torque characteristics (peak torque, angular impulse and deceleration at the hard endpoint) were quantified for nine unskilled joystick operators during the use of a commonly used North American hydraulic-actuation joystick. The six different experimental conditions included combinations of three joystick stiffnesses and two movement speeds. The highest instantaneous input torque over the course of the joystick movement (not including the hard endpoint) was evaluated using the peak torque value. Angular impulse provided an indication of the sustained exposure to force. The third indicator, deceleration at the hard endpoint, was included to provide a description of impact loading on the hand as the joystick came to a sudden stop. The most important result of this work is that the dynamic torque characteristics incurred during hydraulic-actuation joystick use are substantial. While the peak torque values were not very different between the fast and slow motion conditions, the high decelerations even for slow movements observed at maximum excursion of the joystick indicate that the dynamics do matter. On the basis of deceleration at the hard endpoint and peak torque, the joystick movements that require the highest values for a combination of torque variables are the side-to-side ones. This suggests that less stiff balance and return springs should be considered for these directions than for forward and backward movements. However, if the design does not minimize acceleration, it is important that the spring stiffness not be too low since deceleration at the joystick hard endpoint will be very high causing the operator to incur large palm and finger impacts.

Fibre bundle element method of determining physiological cross-sectional area from three-dimensional computer muscle models created from digitised fibre bundle data

Physiological cross-sectional area (PCSA) is used to compare force-producing capabilities of muscles. A limitation of PCSA is that it cannot be measured directly from a specimen, as there is usually no area within the muscle traversed by all fibres. Traditionally, a formula requiring averaged architectural parameters has been used. The purpose of this paper is to describe the development of a fibre bundle element (FBE) method to calculate PCSA from digitised fibre bundle data of five architecturally distinct muscles and compare the FBE and PCSA formula. An FBE method was developed that used a serially arranged set of cylinders as the volumetric representation of each fibre bundle, and PCSA was computed as the summation of the cross-sectional area of each FBE. Four of five muscles had significantly different PCSA between FBE and formula methods. The FBE method provides an approach that considers architectural variances while minimising the need for averaged architectural parameters.

A Review of Factors Influencing Whole-Body Vibration Injuries in Forestry Mobile Machine Operators

Abstract Mobile machine operators in the forestry industry are subjected to long hours of whole-body vibration exposure while adopting static seated postures and performing repeated hand and foot movements to operate controls. These conditions have been found to put operators at increased risk for musculoskeletal injuries and pain in the neck, shoulders, and back, as well as decreased productivity. This paper provides a review of the individual risk factors for these musculoskeletal problems and explores the possible interactions between risk factors and their effects on injury and productivity. Gaps in the literature and directions for future research are identified and discussed.

A systematic approach to simulating field-based occupational whole-body vibration exposure in the lab using a 6df robot

BACKGROUND Whole-body vibration is a significant workplace risk factor for discomfort and injury in many work sectors. The current approach for evaluating vibration exposures typically involves field studies of seatpan acceleration while the operators perform typical workplace activities. These vibration exposures are then compared to international standards to evaluate the risk of discomfort or injury. This approach does not enable systematic and controlled study of specific workplace factors such as the effect of seating, and it is difficult and expensive to perform. APPROACH TO PAPER: We have developed a systematic approach for studying whole-body vibration in the laboratory setting. This approach involves field studies of occupational exposures measuring the 6 degree of freedom chassis accelerations (translational and rotational) and replication of these exposures in the laboratory. FINDINGS To date, as a research team, we have collected chassis vibration data from specific vehicles in the forestry (skidders), mining (load-haul-dump vehicles), and construction (scrapers) sectors. We have processed these exposures to develop a library of representative vibration motions, and have replicated these motions in the laboratory using a robotic platform. CONCLUSIONS This systematic approach of combining field- and laboratory-based measures has facilitated research into specific relevant questions such as the effects of multi axis vibrations on the physical risks to operator health and direct evaluation of the vibration attenuation properties of industrial seats.