Leonard O’Sullivan

Upper-limb surface electro-myography at maximum supination and pronation torques: the effect of elbow and forearm angle.

Forearm pronation and supination, and increased muscular activity in the wrist extensors have been both linked separately to work-related injuries of the upper limb, especially humeral epicondylitis. However, there is a lack of information on forearm torque strength at ranges of elbow and forearm angles typical of industrial tasks. There is a need for strength data on forearm torques at different upper limb angles to be investigated. Such a study should also include the measurement of muscular activity for the prime torque muscles and also other muscles at possible risk of injury due to high exertion levels during tasks requiring forearm torques.Twenty-four male subjects participated in the study that involved maximum forearm torque exertions for the right arm, in the pronation and supination directions, and at four elbow and three forearm rotation angles. Surface EMG (SEMG) was used to evaluate the muscular activity of the pronator teres (PT), pronator quadratus (PQ), biceps brachi (BB), brachioradialis (BR), mid deltoid (DT) and the extensor carpi radialis brevis (ECRB) during maximum torque exertions. Repeated measures ANOVA indicated that both direction and forearm angle had a significant effect on the maximum torques (p<0.05) while elbow angle and the interactions were highly significant (p<0.001). The results revealed that supination torques were stronger overall with a mean maximum value of 16.2 Nm recorded for the forearm 75% prone. Mean maximum pronation torque was recorded as 13.1 Nm for a neutral forearm with the elbow flexed at 45 degrees. The data also indicated that forearm angle had a greater effect on supination torque than pronation torque. Supination torques were stronger for the mid-range of elbow flexion, but pronation torques increased with increasing elbow extension. The strength profiles for the maximum torque exertions were reflected in the EMG changes in the prime supinators and pronators. In addition, the EMG data expressed as the percentage of Maximum Voluntary Electrical activity (MVE), revealed high muscular activity in the ECRB for both supination (26-43% MVE) and pronation torques (17-55% MVE). The results suggest that the ECRB acts as a stabiliser to the forearm flexors for gripping during pronation torques depending on forearm angle, but acts as a prime mover in wrist extension for supination torques with little effect of elbow and forearm angle. This indicates a direct link between forearm rotations against resistance and high muscular activity in the wrist extensors, thereby increasing stress on the forearm musculo-skeletal system, especially the lateral epicondyle.

Neutral lumbar spine sitting posture in pain-free subjects

Sitting is a common aggravating factor in low back pain (LBP), and re-education of sitting posture is a common aspect of LBP management. However, there is debate regarding what is an optimal sitting posture. This pilot study had 2 aims; to investigate whether pain-free subjects can be reliably positioned in a neutral sitting posture (slight lumbar lordosis and relaxed thorax); and to compare perceptions of neutral sitting posture to habitual sitting posture (HSP). The lower lumbar spine HSP of seventeen pain-free subjects was initially recorded. Subjects then assumed their own subjectively perceived ideal posture (SPIP). Finally, 2 testers independently positioned the subjects into a tester perceived neutral posture (TPNP). The inter-tester reliability of positioning in TPNP was very good (intraclass correlation coefficient (ICC) = 0.91, mean difference = 3% of range of motion). A repeated measures ANOVA revealed that HSP was significantly more flexed than both SPIP and TPNP (p <0.05). There was no significant difference between SPIP and TPNP (p > 0.05). HSP was more kyphotic than all other postures. This study suggests that pain-free subjects can be reliably positioned in a neutral lumbar sitting posture. Further investigation into the role of neutral sitting posture in LBP subjects is warranted.

Can we reduce the effort of maintaining a neutral sitting posture? A pilot study

Neutral sitting postures encouraging lumbar lordosis have been recommended in the management of sitting-related low back pain (LBP). However, prolonged lordotic sitting postures can be associated with increased fatigue and discomfort. This pilot study investigated whether changing the type of chair used in sitting can reduce the effort of maintaining a neutral sitting posture. The muscle activation of six trunk muscles was recorded using surface electromyography in 12 painfree participants. Participants were facilitated into a neutral sitting posture for 1 min on both a standard backless office chair and a dynamic, forward-inclined chair (Back App). Lumbar multifidus activity was significantly lower on the Back App chair (p=0.013). None of the other five trunk muscles measured demonstrated a significant difference in activity between the chairs. There was no significant difference (p=0.108) in the perceived effort of maintaining the neutral sitting posture on the two chairs. This study suggests that the lumbar multifidus activation required to maintain a neutral sitting posture can be reduced by considering the type of chair used. The mechanism through which the Back App chair reduces lumbar multifidus activation is unclear, but the greatest difference between chairs is the degree of hip flexion. The ability to maintain a neutral lumbar posture with less lumbar multifidus activation is potentially advantageous during prolonged sitting. Further investigations of the effects of chair design on longer duration sitting, and among LBP subjects, are warranted.

Effects of gender and reach distance on risks of musculoskeletal injuries in an assembly task

Abstract This study investigated differences in elbow and shoulder flexion angles in an assembly task. The experiment involved ten subjects on a simulated assembly task that consisted of seventeen task elements. The locations of the components were at three distances from the subjects. Confidence intervals (90%) were estimated and large differences in risk levels were found when data were pooled from both males and females. Between gender comparisons of joint angles revealed that the male elbow angles were smaller than the females, but the male shoulder angles were greater than the females on average. A within-gender analysis found greater change in angles for the female group with an increase in task distance from the body. This was not the case for the males. This was explained with reference to a previous study that related anthropometrics to differences in joint angles. The shoulder was identified as a joint sensitive to small physical changes in the workplace layout that may make a task more awkward to reach. This was not the case for the elbow. Finally, it was noted that both directions of movement and initial hand location affected final elbow and shoulder joint angles for task elements. Relevance to industry Data is available in the form of anthropometric tables, reach range distances and proposed workstation heights for industry so that differences both between and within genders can be best accommodated for good ergonomic design of workstations. There is a need to supplement this data with information on the variability of induced upper limb joint angles for repetitive assembly tasks within normal reach so as to assist the optimum design of workstations and reduce the likelihood of injuries.

A medical hand tool physical interaction evaluation approach for prototype testing using patient care simulators.

The purpose of this study was to develop and test a physical ergonomics assessment approach for medical device handles. The method assesses wrist posture and force of exertion simultaneously by task element. Electrogoniometers and EMG sensors were connected through a data acquisition module for synchronization with video recordings of trials. Task analysis of video recordings were performed offline with Observer XT software. Average posture and force data across several repetitions of individual task elements were calculated and presented in a format suitable for informing product designers of specific issues during a test trial. A handle comfort questionnaire is proposed to survey subjective responses. The evaluation approach was applied to an endoscope needle in sampling a biopsy from the stomach wall using a gastrointestinal track simulator with ten physician surrogates. The results showed that for all task elements the wrist was in extension (33(°)-45(°)). Peak muscle forces ranged from 28% to 68% MVC across the three muscles studied. Muscle peak forces were above ACGIH HAL maximum threshold limits for four of the seven task elements, and above the action limit for all seven task elements for two muscles. The handle comfort questionnaire data also supported the high muscle force findings, and also on force distribution on the handle due to contact stresses. This combined approach could be used to collect and report detailed early stage ergonomics data from user trials on patient care simulators. The approach is proposed for use by medical device designers at the design stage of new products using prototypes, but it could also be used on existing products with real patients.

User Centered Design and Usability of Bionic Devices

User Centered Design of bionic and assistive devices is growing in importance as many technologies are now moving from lab concepts to certified medical products for use in daily life. The enthusiasm to develop new technologies often focuses on the scientific requirements but often very practical user requirements are over looked. This presentation discusses the role of user centered design in bionics development and how this relates to usability in use. The presentation frames the importance of usability and user centered design on technology acceptance, generally by users, but also with focus on technology acceptance and adoption by older age adults.

XoSoft : a vision for a soft modular lower limb exoskeleton

XoSoft is an EU project that proposes the development of a modular soft lower-limb exoskeleton to assist people with mobility impairments. It aims to be user friendly and comfortable to wear, with a significant impact on the person’s mobility and health, on their independence and quality of life. Being a modular system, it comprises of ankle, knee and hip elements, which can be used individually or combined and used unilaterally or bilaterally.

Technology Acceptance and User-Centred Design of Assistive Exoskeletons for Older Adults: A Commentary

Assistive robots are emerging as technologies that enable older adults to perform activities of daily living with autonomy. Exoskeletons are a subset of assistive robots that can support mobility. Perceptions and acceptance of these technologies require understanding in a user-centred design context to ensure optimum experience and adoption by as broad a spectrum of older adults as possible. The adoption and use of assistive robots for activities of daily living (ADL) by older adults is poorly understood. Older adult acceptance of technology is affected by numerous factors, such as perceptions and stigma associated with dependency and ageing. Assistive technology (AT) models provide theoretical frameworks that inform decision-making in relation to assistive devices for people with disabilities. However, technology acceptance models (TAMs) are theoretical explanations of factors that influence why users adopt some technologies and not others. Recent models have emerged specifically describing technology acceptance by older adults. In the context of exoskeleton design, these models could influence design approaches. This article will discuss a selection of TAMs, displaying a chronology that highlights their evolution, and two prioritised TAMs—Almere and the senior technology acceptance model (STAM)—that merit consideration when attempting to understand acceptance and use of assistive robots by older adults.

Toward a Model of Human Information Processing for Decision-Making and Skill Acquisition in Laparoscopic Colorectal Surgery

OBJECTIVE To create a human information-processing model for laparoscopic surgery based on already established literature and primary research to enhance laparoscopic surgical education in this context. DESIGN We reviewed the literature for information-processing models most relevant to laparoscopic surgery. Our review highlighted the necessity for a model that accounts for dynamic environments, perception, allocation of attention resources between the actions of both hands of an operator, and skill acquisition and retention. The results of the literature review were augmented through intraoperative observations of 7 colorectal surgical procedures, supported by laparoscopic video analysis of 12 colorectal procedures. RESULTS The Wickens human information-processing model was selected as the most relevant theoretical model to which we make adaptions for this specific application. We expanded the perception subsystem of the model to involve all aspects of perception during laparoscopic surgery. We extended the decision-making system to include dynamic decision-making to account for case/patient-specific and surgeon-specific deviations. The response subsystem now includes dual-task performance and nontechnical skills, such as intraoperative communication. The memory subsystem is expanded to include skill acquisition and retention. CONCLUSIONS Surgical decision-making during laparoscopic surgery is the result of a highly complex series of processes influenced not only by the operators knowledge, but also patient anatomy and interaction with the surgical team. Newer developments in simulation-based education must focus on the theoretically supported elements and events that underpin skill acquisition and affect the cognitive abilities of novice surgeons. The proposed human information-processing model builds on established literature regarding information processing, accounting for a dynamic environment of laparoscopic surgery. This revised model may be used as a foundation for a model describing robotic surgery.

The potential and acceptance of exoskeletons in industry

Worldwide, a significant interest in wearable robots or exoskeletons does exist, also from an industrial background. This paper provides an overview of assistive exoskeletons that have specifically been developed for industrial purposes. It discusses their potential in increasing performance and flexibility on one hand and in reducing the mechanical loads on workers involved in manual work on the other. From this it is concluded that exoskeletons have the potential to increase performance under specific conditions and to reduce physical loads significantly. However, several technical issues hinder mainstay practical use of exoskeletons in industry until now. One main issue concerns the human-machine interaction which stands in the way of acceptance. This issue and its linkage to ethics and standardization will be discussed during the conference.