A Preliminary Study on Ergonomic Contribution to the Engineering Design Approach of a Wheel Loader Control Lever System

Studies show that heavy machinery operators are exposed to risk factors of musculoskeletal diseases. However, there has yet to be a study investigating the grip analysis of heavy machinery control levers. This preliminary study aims to investigate the grip analysis of a system that emulates the push–pull operations, handle shapes, and resistance of wheel loader control lever systems. The system was designed, analysed, and optimised using Autodesk Inventor 2019 before fabrication and testing. It underwent usability testing for estimated and perceived grip force analysis (ergonomics analysis). The tests measured estimated force using a sensor glove, and perceived force using the Borg CR10 scale. The data were analysed using regression and paired t-tests. The findings suggested that pulling and high resistance factors required higher estimated force (339.50 N) and perceived force (5.625) than pushing and low resistance factors in manoeuvring the system (p < 0.05). The cylindrical handle required more estimated force (339.50 N) but less perceived force (4.5) than the spherical handle due to ergonomic design considerations (p < 0.05). Although there were inaccuracies in force measurement methods, the perceived method was still effective for data collection, since it is challenging to measure grip force in a real situation with heavy machinery. While this study was only a simulation, it provided researchers with ideas that may solve problems in the manipulation of heavy machinery control levers.

Medicalisation and the Treatment-Enhancement Distinction in the Ethical Debate on Gene Editing

"Since the advent of CRISPR/Cas9 gene editing technology, much bioethical effort has been devoted to prescribing the appropriate potential uses of gene editing in humans. Frequently in the literature, a normative distinction is drawn between “treatment” and “enhancement”. That is, gene editing may be morally acceptable or even morally required if used to cure a disease or genetic condition. For enhancement, however, it is morally unacceptable, having too weak a justification for the risks involved. In the context of this new technology, we all thus become vulnerable to a bias: medicalisation. There are clear non-medical benefits, as I show here, of using gene editing not for treatment, but for enhancement. Many individuals and governments will wish to pursue these benefits, but if we are ethically constrained by the current perceived force of the treatment-enhancement distinction, we may be prevented from legitimately doing so. We are faced with two options: firstly, to reject the distinction presented by many ethicists, and pursue gene editing for both treatment and enhancement purposes; secondly, to expand medical definitions and the scope of health care, to include the sort of benefits that we might wish were included under “treatment”. The first option, I argue, is to be preferred, but at least currently, faces much public resistance. Instead, we risk the second option becoming the norm, with the medicalisation of scores of non-medical characteristics drawing resources, causing anxiety, and burdening health care systems, because of stubborn adherence to an arbitrary distinction in the gene editing debate. "

Gender-Based Differences in Actual Thumb Force Exertions at Various Target Force Levels

Measurement of thumb force in the industrial filed is important to quantify the risk of manual tasks. However, few studies have assessed the thumb force. Therefore, the purpose of this study was to investigate the relationship between actual thumb force and perceived force according to the force levels and gender. A total of 31 healthy participants (23 males and 8 females) were asked to exert a maximum thumb force (MTF) and random levels of target thumb force (10, 30, 50, 70, and 90% MTF). Results indicated that females exerted approximately 73.6% (100.6 N) of the strength exerted by males (136.7 N). Based on the differences between actual and perceived thumb exertions, the highest accuracy was achieved at 50% MTF, designated as “50%-phenomenon”. At 10% and 30% MTF levels, participants tended to exert greater strength (over-exertion) than the perceived exertions, whereas participants showed less strength (under-exertion) than the perceived exertions at 70% and 90% MTFs. Participants generally exerted greater and lesser thumb force than the perceived exertions at levels lower and higher than 50% MTF, respectively. Thus, the relationship between the actual and perceived force of exertion displayed a nonlinear S-shaped curve.

Force illusions and drifts observed during muscle vibration

We explored predictions of a scheme that views position and force perception as a result of measuring proprioceptive signals within a reference frame set by ongoing efferent process. In particular, this hypothesis predicts force illusions caused by muscle vibration and mediated via changes in both afferent and efferent components of kinesthesia. Healthy subjects performed accurate steady force production tasks by pressing with the four fingers of one hand (the task hand) on individual force sensors with and without visual feedback. At various times during the trials, subjects matched the perceived force using the other hand. High-frequency vibration was applied to one or both of the forearms (over the hand and finger extensors). Without visual feedback, subjects showed a drop in the task hand force, which was significantly smaller under the vibration of that forearm. Force production by the matching hand was consistently higher than that of the task hand. Vibrating one of the forearms affected the matching hand in a manner consistent with the perception of higher magnitude of force produced by the vibrated hand. The findings were consistent between the dominant and nondominant hands. The effects of vibration on both force drift and force mismatching suggest that vibration led to shifts in both signals from proprioceptors and the efferent component of perception, the referent coordinate and/or coactivation command. The observations fit the hypothesis on combined perception of kinematic-kinetic variables with little specificity of different groups of peripheral receptors that all contribute to perception of forces and coordinates. NEW & NOTEWORTHY We show that vibration of hand/finger extensors produces consistent errors in finger force perception. Without visual feedback, finger force drifted to lower values without a drift in the matching force produced by the other hand; hand extensor vibration led to smaller finger force drift. The findings fit the scheme with combined perception of kinematic-kinetic variables and suggest that vibration leads to consistent shifts of the referent coordinate and, possibly, of coactivation command to the effector.

A Model of Early Motivational States and Their Uses

A model of early development of motivational states is proposed. The states are modeled in terms of modern concepts of state space and are physically realized by long-term-potentiation (LTP)-based neural circuits. The basic idea is to assume existence of libido and aggression instincts that would receive single sensory stimulus and induce capabilities for fight-or-flight, freeze or run, etc. The libido state may lead to happiness, contentment, or activities such as dance or play, imitation of observed behavior and action of others, and engagement in learning by trial and error.Enhancement of two motor skills are presented: responding more quickly in time and delivering a larger force of contact. This is a simple example of how the perception system, the motor system and the motivation system interact. A one-degree-of-freedom second-order mechanical system is modified by a first-order neural facilitator or compensator.The tit-for-tat phenomenon in force escalation is also modeled. The model includes tactile sensors for the measurement of a known force applied to a human finger, afferent transmission of the sensed force to the brain, storage of the perceived force, recovery of the stored force from memory, and efferent transmission of the force to the finger. The situation may change based on perception of more adversaries discouraging retaliation and encouraging resort to withdrawal and / or retreat.