Susan Hallbeck

The effect of a lightweight massage system in a car seat on comfort and electromyogram.

OBJECTIVE The objective of this study was to determine the effect of a lightweight low-intensity massage system (LWMAS) in a car seat on the electromyogram (EMG) of the neck and shoulder muscles and on the comfort experience during driving. METHODS Two experiments were performed during driving with and without the active LWMAS in the seat. Subjective measurements were taken, in which the comfort experience was recorded for 20 participants driving a prescribed path around Munich for 120 minutes. Then objective (surface EMG above the rhomboideus and trapezius muscles) measurements and subjective measurements of the comfort experience were recorded over 7 laps on a test track for 24 participants. RESULTS The comfort was higher, and the EMG was significantly lower in the trapezius area while driving with the LWMAS. CONCLUSION Despite the fact that the LWMAS system is lightweight, has low intensity, and might have had a smaller effect, similar effects to previous studies with heavier systems were found, indicating that this massage system increases comfort and reduces muscle activity during driving as well.

A comparison of muscular activity during single and double mouse clicks

Work-related musculoskeletal disorders (WMSDs) in the neck/shoulder region and the upper extremities are a common problem among computer workers. Occurrences of motor unit (MU) double discharges with very short inter-firing intervals (doublets) have been hypothesised as a potential additional risk for overuse of already exhausted fibres during long-term stereotyped activity. Doublets are reported to be present during double-click mouse work tasks. A few comparative studies have been carried out on overall muscle activities for short-term tasks with single types of actions, but none on occurrences of doublets during double versus single clicks. The main purpose of this study was to compare muscle activity levels of single and double mouse clicks during a long-term combined mouse/keyboard work task. Four muscles were studied: left and right upper trapezius, right extensor digitorum communis (EDC) and right flexor carpi ulnaris. Additionally, MU activity was analysed through intramuscular electromyography in the EDC muscle for a selection of subjects. The results indicate that double clicking produces neither higher median or 90th percentile levels in the trapezius and EDC muscles, nor a higher disposition for MU doublets, than does single clicking. Especially for the 90th percentile levels, the indications are rather the opposite (in the EDC significantly higher during single clicks in 8 of 11 subjects, P<0.05). Although it cannot be concluded from the present study that double clicks are harmless, there were no signs that double clicks during computer work generally constitute a larger risk factor for WMSDs than do single clicks.

Effects of Interdigital Spacing, Wrist Position, Forearm Position, Grip Span, and Gender on Static Grip Strength

To analyze the effects of factors which may decrement static grip strength, a study was performed using 20 subjects (10 males and 10 females). Three levels of interdigital spacing were examined: 0, 4, and 8 mm to correspond to bare hand, a thermal/spectra knit layered glove, and a chemical glove. Three wrist positions (neutral, 45 degree extension, and 45 degree flexion) and three forearm positions (neutral, full supination, and full pronation), as well as two levels of grip spacing (6.1 and 7.4 cm on the hand dynamometer) were varied in the study. Thus, each subject performed 54 trials, which were presented in random order. The results indicate that the following were significant main effects: gender, grip span, forearm position, wrist position, and interdigital spacing. As expected, males exerted 63.7% more strength, on average, than females. Also, full pronation had a significantly lower mean grasp strength than either neutral or full supination. The 8 mm spacing differed significantly from both 0 and 4 mm spacing and both 4 and 8 mm spacing had a lower mean grasp strength than 0 mm. Also, the 7.4 cm position on the hand dynamometer had significantly lower mean grasp strength as compared with the 6.1 cm position. Wrist position affected mean grasp strength as well; with a neutral wrist position, the strength was significantly higher than either flexed or extended, with a greater decrement from flexion than extension.

A Comprehensive Methodology for Examining the Impact of Surgical Team Briefings and Debriefings on Teamwork

The adoptions of briefing and debriefing protocols have evolved from the Joint Commission’s initiative to improve communication and safety in the operating room. Briefing normally occurs prior to incision and is used to discuss and confirm critical information, while debriefing occurs during or after surgery. Debriefing provides a unique opportunity for individuals and teams to immediately reflect on their performance, allowing them to more easily identify errors and develop plans to improve their next performance. Studies have shown that using briefings and debriefings improve communication and teamwork. However, there is still much to learn about the value of both for surgical teams. This paper presents a robust methodology for examining and measuring the impacts of surgical team briefings and debriefings on teamwork. The methodology includes (1) audio/video recording the surgical care process, (2) prospective observations using a validated electronic data collection tool, (3) pre- and post-surgery surveys, and (4) individual surgical team member interviews. The current paper describes the methodology to obtain a robust and comprehensive data set for analyzing the impacts of briefing and debriefing on teamwork; the results of the surgeries recorded using this methodology will be presented in subsequent papers.

Corporate Ergonomics Programs: Identifying Value through a Company Award Process

OCCUPATIONAL APPLICATIONS The application of ergonomics principles can reduce the number, severity, and costs of work-related musculoskeletal disorders. Increasingly, academic and practitioner research demonstrates that ergonomic improvements also contribute to manufacturing operating efficiency and a companys profitability. This article examines whether it is possible to identify business benefits achieved through ergonomics interventions via an ergonomics award process. The projects, conducted independently at numerous manufacturing locations and submitted to a global companys internal ergonomics award process, were reviewed for effect upon both work-related musculoskeletal disorders and operational efficiency. The results suggest the award process was successful in gathering relevant information about the projects, and that a macroergonomics program methodology along with a participatory approach supported successful results. A cost-benefit estimation showed positive effects in operational efficiency and work-related musculoskeletal disorders reduction. Possible improvements to the award submission process were identified. TECHNICAL ABSTRACT Background: As documented by academics and practitioners, and generally accepted by the popular media, application of ergonomics principles can reduce the number, severity, and costs of work-related musculoskeletal disorders. Research increasingly demonstrates that ergonomic improvements also contribute to manufacturing operating efficiency and a companys profitability. Purpose: To expand the body of practitioner-based knowledge related to the benefits that may be realized through implementing an ergonomics program in industry, focusing on the physical aspects of work. Specifically considered is the importance of a macroergonomic, company-wide process to define how risk assessments are conducted, how interventions are chosen and measured, and how results are summarized. Method: Eighteen case studies, selected from among 166 submitted to a global manufacturing companys internal ergonomics award process were reviewed. Results: A macroergonomics program methodology, in combination with a participatory approach, supported success in terms of reduced work-related musculoskeletal disorder risk and operational efficiency. Specifically, information about how projects were identified and who participated as team members demonstrates the importance of a participatory approach to achieve positive results. Conclusion: The case study results, based upon a practitioner perspective, suggest that operational efficiency and work-related musculoskeletal disorder reduction are often both improved by ergonomic interventions in the workplace, which is consistent with similar findings in earlier research. However, requiring more specific and standardized cost and benefit information in an award submission process is likely to provide more complete information about project results in a manner of value to practitioners, academia, and business. A future challenge is to gain more specific information in a manner that does not significantly add to the workload of individuals leading the projects who, in these case studies, have many responsibilities beyond ergonomics. A collaborative effort between practitioners and researchers to create and test such a method would be of value to both.

How should Trackball Directional Movement Intuitively Relate to an End Effector

Three strategies for the trackball control of an end effector on a laparoscopic graspers tool were tested to see which strategy was most intuitive to the user. The three strategies (UURR, UDRL, UDRR) were tested on four different orientations of the hand: horizontal holding the tool as an extension of the arm while rolling the trackball with the thumb, horizontal holding the tool as an extension of the arm and forearm pronated 90 degrees while rolling with the thumb, horizontal with tool 90° to arm using the thumb, and horizontal with tool 90° to arm using the index finger to roll the ball. Twenty-four subjects, each randomly chosen to test one of the three movement strategies, performed two trials sets per hand orientation, the first to test for intuition and the second to test for the effect of training. The outcome of the trials was a number of correct and incorrect movements of the trackball to control the end effector which was simulated on a computer screen. The results were analyzed using a general linear model test on repeated measures to determine the effects of strategy and hand orientation. Analyses showed that intuitively, subjects were significantly better when the end effector moved as the trackball did (UURR). The analyses of the learned trials showed that subjects did equally well with all three strategies. From these results, it was determined that the trackball control of the forceps will be manipulated using the UURR strategy.

Mental and physical workloads in a competitive laparoscopic skills training environment: A pilot study

Surgical trainees undergo demanding training to achieve high surgical task proficiency. Abounding clinical and educational responsibilities mandate efficient and effective training. This research measured resident workload during laparoscopic skills training to identify excessive workload and how workload impacted task performance. Twenty-eight surgical trainees performed a standardized surgical training task and completed a workload questionnaire while observers measured physiological stress, posture risk assessment, and task performance. Participants self-reported mental demands, physical demands, temporal demands, performance, effort, and frustration. Effort (12±4) and frustration (12±5) were the highest subscales while physical demand (8±4) was the lowest. All participants were observed performing the task in at-risk postures, with 21% exhibiting risk levels requiring immediate intervention. Physical demand was associated with posture risk assessment scores (p<0.05). Mental demand was positively (R2=0.20, p<0.05) and frustration was negatively (R2=0.18, p<0.05) associated with skin conductance range. A point increase in physical demand was associated with a six second increase in performance time (β=6.0, p=0.01). These results support the fact that human factors and ergonomic tools can be used to relate surgical skills performance with workload, stress, and posture risks.

A Preliminary Study of Novice Workload and Performance During Surgical Simulation Tasks for Conventional vs. Single Incision Laparoscopic Techniques

Laparoendoscopic single site surgery (LESS) can provide potential patient benefits beyond conventional laparoscopy (CL). However, LESS further exacerbates current ergonomic disadvantages of CL. LESS practices to compensate for the constraints include intracorporeal crossing of instruments (UL) for improved manipulation of instrumentation and extracorporeal crossing of hands (PL) for illusion mitigation. Preliminary results from this study involving 12 medical students (7 males) performing a simulated surgical task found statistical difference between CL, PL, and UL for physical demand (P<0.001), task complexity (P=0.002) and performance times (P<0.001) with no difference for mental demand (P=0.106). These initial findings show that the PL technique cannot currently compensate for the limitations of LESS to make UL more similar to CL. Further research is needed to determine if PL or another LESS compensatory practice can allow surgeons to more effectively perform procedures with a single port and therefore ensure patients reap its benefits.

Psychophysical measures of exertion. Are they muscle group dependent

The purpose of the present study was to evaluate the applicability of the RPE (CR-10) scale for a number of physical exertions which employ only the upper limb with a variety of muscle group sizes and exertion levels. Ten female and ten male subjects performed pinch and pulling tasks in which four different muscle groups were engaged employing the finger, wrist, forearm and the whole arm. MVC (maximum voluntary contraction) exertion levels, RPE (Borgs CR-10 scale) value, and accuracy of the subjective assessment were measured. The results indicate that the accuracy of psychophysical measures are not muscle dependent although force generating capability is dependent on the muscle group involved. Female subjects were found more accurate in their perception of perceived exertion at lower levels of exertion than male subjects. It also appears that the RPE rating can be used to assess a variety of exertion levels accurately for a range of tasks, involving a range of muscle group sizes and location.

Physician Interruptions and Workload during Emergency Department Shifts

Interruptions in the Emergency Department (ED) are moderately studied in regard to their impact on physicians’ workload. This study captured interruptions characteristics and measures of workload. Twenty-eight ED physicians were followed during their shifts; interruptions they faced were captured using a validated tablet PC-based tool. At the mid and end of their shift, providers completed a NASA-Task Load Index (TLX) questionnaire and a reaction time task. Descriptive statistics and ANOVA were used to identify relationships between physicians’ interruptions and workload. A total of 2355 interruptions were identified (M =84.1, SD =14.5). The NASA-TLX results showed increase in physicians’ responses for all subscales from mid to end-shifts. Reaction time was higher at end-shift with mean difference of 33.75ms, 95% CI [20.35, 47.13], p < 0.001. At end-shift, there was a statistically significant positive correlation between reaction time and all NASA-TLX subscales. Interruption duration rather than frequency correlated positively with NASA-TLX scores. High/critical interruptions were the least frequent but had longer duration and greater impact on workload. This study provided a unique examination of interruptions over an entire provider shift and identified interruptions as potential causes of increased workload for ED physicians.