What are the Top Research Priorities in Surgical Simulation and How Can They Be Best Addressed? Results From a Multidisciplinary Consensus Conference.

OBJECTIVES: To define the top priorities in simulation-based surgical education where additional research would have the highest potential to advance the field and develop proposals that would address the identified research priorities. SUMMARY AND BACKGROUND DATA: Simulation has become integral part of surgical training but there are a number of outstanding questions that have slowed advances in this field. METHODS: The Delphi methodology was used to define the top priorities in simulation-based surgical education. A research summit was held with multiple stakeholders under the auspices of the American College of Surgeons Division of Education to develop proposals to address these priorities. RESULTS: Consensus was achieved after the first round of voting on the following 3 most important topics: (1) impact of simulation training on patient safety and outcomes, (2) the value proposition of simulation, and (3) the use of simulation for physician certification and credentialing. Knowledge gaps, challenges and opportunities, and research questions to address these topics were defined by summit participants. CONCLUSIONS: The top 3 priorities in surgical simulation research were defined and project outlines were developed for impactful projects on these topics. Successful completion of such projects is expected to advance the field of simulation-based surgical education.

Can a virtual reality surgical simulation training provide a self-driven and mentor-free skills learning? Investigation of the practical influence of the performance metrics from the virtual reality robotic surgery simulator on the skill learning and associated cognitive workloads.

BACKGROUND: While it is often claimed that virtual reality (VR) training system can offer self-directed and mentor-free skill learning using the system's performance metrics (PM), no studies have yet provided evidence-based confirmation. This experimental study investigated what extent to which trainees achieved their self-learning with a current VR simulator and whether additional mentoring improved skill learning, skill transfer and cognitive workloads in robotic surgery simulation training. METHODS: Thirty-two surgical trainees were randomly assigned to either the Control-Group (CG) or Experiment-Group (EG). While the CG participants reviewed the PM at their discretion, the EG participants had explanations about PM and instructions on how to improve scores. Each subject completed a 5-week training using four simulation tasks. Pre- and post-training data were collected using both a simulator and robot. Peri-training data were collected after each session. Skill learning, time spent on PM (TPM), and cognitive workloads were compared between groups. RESULTS: After the simulation training, CG showed substantially lower simulation task scores (82.9 ± 6.0) compared with EG (93.2 ± 4.8). Both groups demonstrated improved physical model tasks performance with the actual robot, but the EG had a greater improvement in two tasks. The EG exhibited lower global mental workload/distress, higher engagement, and a better understanding regarding using PM to improve performance. The EG's TPM was initially long but substantially shortened as the group became familiar with PM. CONCLUSION: Our study demonstrated that the current VR simulator offered limited self-skill learning and additional mentoring still played an important role in improving the robotic surgery simulation training.

Does treadmill walking with near-infrared light applied to the abdominal area reduce local adiposity and body weight?

[Purpose] The purpose of this study was to determine the effect on local fat deposition and body weight of wearing a near-infrared light belt around the abdomen. [Subjects and Methods] Twenty-eight obese female subjects participated in this experiment. For measurement of body composition, an impedance-style body fat analyzer was used. The experimental group performed treadmill walking 3 times per week for 12 weeks while wearing an activated near-infrared belt around the abdomen. The near-infrared belt was composed of light-emitting diodes having wavelengths of 630 nm, 830 nm, 880 nm, and 956 nm. [Results] The analysis of abdominal circumference indicated that the abdominal circumference of the experimental group was reduced in post-test measurements compared to pre-test. [Conclusion] This investigation showed significant reductions in abdominal circumference, abdominal fat percentage, fat mass, and body-mass index for the experimental compared to the control group, suggesting that changes in body composition can be enhanced when near-infrared radiation is applied to the abdomen during walking.

Effects of assisted aquatic movement and horseback riding therapies on emotion and brain activation in patients with cerebral palsy.

[Purpose] The purpose of this study was to determine the effects of assisted aquatic movement and horseback riding therapies on emotion and brain activation in patients with cerebral palsy. [Subjects and Methods] Thirty-two right-handed patients with cerebral palsy (18 male, 14 female) whose ages ranged from 8 to 48 years participated in this experiment. Their cerebral palsy levels ranged from 1 to 3. The participants were assigned to one of three groups according to the experimental conditions: an assisted aquatic movement therapy group, a horseback riding therapy group, or a control group. Electroencephalograms, the Feeling Scale and the Felt Arousal Scale were examined as dependent variables. [Results] Analysis of self-reported data demonstrated a significant positive improvement in the emotions of participants in the assisted aquatic movement therapy group in comparison with the control group. With regard to the electroencephalogram analysis, the results of this study showed increased alpha power in the assisted aquatic movement therapy group compared with the horseback riding and control groups. [Conclusion] The results of this study suggest that professionals can consider assisted aquatic movement therapy as an effective therapeutic intervention for the improvement of mental health and brain activation.

The ergonomics of women in surgery.

BACKGROUND: Among surgeons who regularly perform minimally invasive surgery, as many as 87 % report injuries or symptoms related to job performance. Operating room and instrument design have traditionally favored surgeons who are taller and who possess hands that are, in general, large and strong. We hypothesize that women may be experiencing more ergonomic difficulties than men for whom the operating room and surgical instruments, although uniformly perilous, more traditionally have accommodated. METHODS: A 23-item web-based survey was offered via email to 2,000 laparoscopic surgeons and fellows currently practicing. The survey addressed four categories: demographics, physical symptoms, ergonomics, and environment/equipment. Key questions allowed us to identify which body part experienced which symptoms. RESULTS: There was a 15.7 % overall response rate. Among respondents, 17 % (54/314) were female. Women were significantly younger, shorter, had smaller glove size, and fewer years in practice than men surveyed (all p values < 0.0001). Of women reporting, 86.5 %­comparable to men­attribute physical discomfort to laparoscopic operating. Female surgeons are more likely to receive treatment for their hands, which includes the wrist, thumb, and fingers (odds ratio 3.5, p = 0.028). When men and women of the same glove size were compared, women with a larger glove size (7­8.5) reported more cases of treatment for their hands than men of the same glove size. (21 vs. 3 %, p = 0.016). Women who wore a size 5.5­6.5 surgical glove reported significantly more cases of discomfort in their shoulder area (neck, shoulder, upper back) than men who wore the same size surgical glove (77 vs. 27 %, p = 0.004). CONCLUSIONS: Women surgeons are experiencing more discomfort and treatment in their hands than male surgeons. Redesign of laparoscopic instrument handles and improvements to table height comprise the most promising solutions to these ergonomic challenges.

Comparative assessment of physical and cognitive ergonomics associated with robotic and traditional laparoscopic surgeries.

BACKGROUND: We conducted this study to investigate how physical and cognitive ergonomic workloads would differ between robotic and laparoscopic surgeries and whether any ergonomic differences would be related to surgeons' robotic surgery skill level. Our hypothesis is that the unique features in robotic surgery will demonstrate skill-related results both in substantially less physical and cognitive workload and uncompromised task performance. METHODS: Thirteen MIS surgeons were recruited for this institutional review board-approved study and divided into three groups based on their robotic surgery experiences: laparoscopy experts with no robotic experience, novices with no or little robotic experience, and robotic experts. Each participant performed six surgical training tasks using traditional laparoscopy and robotic surgery. Physical workload was assessed by using surface electromyography from eight muscles (biceps, triceps, deltoid, trapezius, flexor carpi ulnaris, extensor digitorum, thenar compartment, and erector spinae). Mental workload assessment was conducted using the NASA-TLX. RESULTS: The cumulative muscular workload (CMW) from the biceps and the flexor carpi ulnaris with robotic surgery was significantly lower than with laparoscopy (p < 0.05). Interestingly, the CMW from the trapezius was significantly higher with robotic surgery than with laparoscopy (p < 0.05), but this difference was only observed in laparoscopic experts (LEs) and robotic surgery novices. NASA-TLX analysis showed that both robotic surgery novices and experts expressed lower global workloads with robotic surgery than with laparoscopy, whereas LEs showed higher global workload with robotic surgery (p > 0.05). Robotic surgery experts and novices had significantly higher performance scores with robotic surgery than with laparoscopy (p < 0.05). CONCLUSIONS: This study demonstrated that the physical and cognitive ergonomics with robotic surgery were significantly less challenging. Additionally, several ergonomic components were skill-related. Robotic experts could benefit the most from the ergonomic advantages in robotic surgery. These results emphasize the need for well-structured training and well-defined ergonomics guidelines to maximize the benefits utilizing the robotic surgery.

A review of the American College of Surgeons accredited education institutes' assessment practices for learners, faculty, and continuous program improvement.

Purpose: Simulation is an instructional modality that offers opportunities for assessment across many domains. The American College of Surgeons created the Accredited Education Institutes (AEIs) to build a community of high-quality simulation centers focused around improving surgical education and training. The goals of this project were to identify assessment methods used by AEIs, discuss how these methods align with established assessment frameworks, identify best practices, and provide guidance on best practice implementation. Methods: The authors analyzed responses regarding learner assessment, faculty assessment, and continuous program improvement from AEI accreditations surveys using deductive qualitative analysis. Results: Data from ninety-six centers were reviewed. Codes for each category were organized into formal and informal themes. For learner assessment, examinations and checklists identified as the most common types of formal assessment used and oral feedback as the most common type of informal assessment. For faculty assessment, written evaluations were the most common formal type and debriefs were the most common informal type. For continuous program improvement, written evaluations were the most common formal type and oral feedback was the most frequent informal type. Discussion: The goal of assessment should be to encourage learning through feedback and to ensure the attainment of educational competencies. The data revealed a variety of assessment modalities used to accomplish this goal with AEIs frequently utilizing some of the most reliable forms of assessment. We discuss how these forms of assessment can be integrated with best practices to develop assessment portfolios for learners and faculty, performance improvement reports for faculty, and assessments of clinical impact. Supplementary Information: The online version contains supplementary material available at 10.1007/s44186-023-00132-6.

Quantifying mental workloads of surgeons performing natural orifice transluminal endoscopic surgery (NOTES) procedures.

BACKGROUND: During natural orifice transluminal endoscopic surgery (NOTES), surgeons often have difficulties orienting the surgical view and manipulating instruments accurately, which increases their level of mental and physical fatigue. This study quantified mental workload by measuring the spared mental resources of surgeons performing NOTES training tasks. METHODS: Assessment of mental workload was conducted in both a benchtop and a hybrid animal model. Using the benchtop model, surgeons were required to pass a ring as many times as possible in 6 min. Using the hybrid model, surgeons were required to dissect the gallbladder. While performing those primary tasks, the surgeon was required to identify true visual signals among many false signals displayed on an adjacent monitor. They were asked to repeat the trials using laparoscopy. The surgeons' performance on the primary and secondary tasks using the NOTES and laparoscopic approaches were recorded and compared. RESULTS: The nine surgeons who completed the trials in the benchtop model successfully transferred 13 ± 4 rings between targets using laparoscopy compared with a mean of 1.2 ± 1.0 rings transferred using NOTES (P < 0.001). The surgeons detected visual signals at a 74% rate using laparoscopy, which was significantly higher than the 54% detection rate with the NOTES procedure (P = 0.005). Using the hybrid model, 10 surgeons achieved a 55% accuracy rate performing the laparoscopic task. This was found to be significantly higher (P = 0.006) than when the task was performed using the NOTES platform (39%). CONCLUSION: The results showed that performance of a task using the NOTES platform increases surgeons' mental workload. Because difficulty performing NOTES is associated with flexible endoscopy, the authors expect that new operating systems providing stable platforms will help to decrease the mental workload of surgeons and enhance eye-hand coordination in performing NOTES.

Higher physical workload risks with NOTES versus laparoscopy: a quantitative ergonomic assessment.

BACKGROUND: Research confirms that surgeons experience physical symptoms due to the unfavorable ergonomics of laparoscopy. The physical effects of performing Natural Orifice Transluminal Endoscopic Surgery (NOTES)-potentially the next evolutionary surgical step-are only now being quantitatively and systematically assessed. This study investigates NOTES- and laparoscopy-related physical workloads through biomechanical analyses. METHODS: Fourteen surgeons with varying laparoscopic experience were recruited. Each participant completed ring transfer and triangle transfer tasks using two surgical platforms: laparoscopy and NOTES. Motion capture and electromyography (EMG) systems recorded biomechanical data for quantitative physical workload assessment. The normalized cumulative muscular workload (NCMW) and mean muscular workload (MMW) were obtained from EMG data. Then normalized performance time (NPT) was compared between the two surgical platforms. The overall NCMW was considerably greater when participants performed tasks using the NOTES platform (1315.8±116.9%) compared with traditional laparoscopy (153.9±18.8%). RESULTS: Performing NOTES required eight to nine times higher muscular workload (NCMW: NOTES 1315.8%, laparoscopy 153.9%, p<0.05) when compared with traditional laparoscopy. This result was shown to be caused by the following: (1) six to eight times longer NPT with NOTES (p<0.05) and (2) higher average activation levels shown in regard to biceps, extensor digitorum communis, and thenar compartment (p<0.05), the muscles responsible for specific joint movements to hold and operate the scope. CONCLUSION: This study demonstrated that performing NOTES is significantly more challenging for surgeons than laparoscopy. The greater amount of muscular exertion required is linked to higher ergonomic risks. Based on the depth and strength of our results, we propose that an alternative NOTES platform be designed, one that overcomes the awkward operational mechanism of the dual-working-channel flexible endoscope.

A validated subjective rating of display quality: the Maryland Visual Comfort Scale.

BACKGROUND: Minimally invasive surgery requires high-quality imaging to provide effective visual displays to surgeons. Whereas objective measures--pixels, resolution, display size, contrast ratio--are used to compare imaging systems, there are no tools for assessing the perceptual impact of these physical measures. We developed the "Maryland Visual Comfort Scale" (MVCS) to measure perceptual qualities in relation to an imaging system. We theorize that what the surgeon perceives as a high-quality image can be summarized by a scoring of seven characteristics related to human perception, and that image quality is not homogenous across a video display such that object location impacts perception and display quality. METHOD: We created a rating scale for seven dimensions of display characteristics (contrast, detail, brightness, lighting uniformity, focus uniformity, color, sharpness). For validation, 30 participants viewed test patterns and manipulated physiologic images, rating the image quality for all seven dimensions as well as giving an overall rating. Image ratings for contrast and detail dimensions were assessed across five locations on the video display. For ratings, two imaging systems were used, differing primarily in the 10-mm zero-degree scope's quality: a standard scope and one taken from service for quality degradation. RESULTS: The rating scale was sensitive to differences in scope quality for all seven items in the MVCS (all p values<0.01). Significant differences existed between quality ratings at central and peripheral locations (p<0.05). CONCLUSIONS: This seven-item rating scale for assessing visual comfort is reliable and sensitive to scope quality differences. The scale is sensitive to degradation of image quality at video display edges. These seven dimensions of display characteristics can be refined to create a psychometric to serve as a composite of perceptual quality in laparoscopy.

Laparoscopic cholecystectomy poses physical injury risk to surgeons: analysis of hand technique and standing position.

BACKGROUND: This study compares surgical techniques and surgeon's standing position during laparoscopic cholecystectomy (LC), investigating each with respect to surgeons' learning, performance, and ergonomics. Little homogeneity exists in LC performance and training. Variations in standing position (side-standing technique vs. between-standing technique) and hand technique (one-handed vs. two-handed) exist. METHODS: Thirty-two LC procedures performed on a virtual reality simulator were video-recorded and analyzed. Each subject performed four different procedures: one-handed/side-standing, one-handed/between-standing, two-handed/side-standing, and two-handed/between-standing. Physical ergonomics were evaluated using Rapid Upper Limb Assessment (RULA). Mental workload assessment was acquired with the National Aeronautics and Space Administration-Task Load Index (NASA-TLX). Virtual reality (VR) simulator-generated performance evaluation and a subjective survey were analyzed. RESULTS: RULA scores were consistently lower (indicating better ergonomics) for the between-standing technique and higher (indicating worse ergonomics) for the side-standing technique, regardless of whether one- or two-handed. Anatomical scores overall showed side-standing to have a detrimental effect on the upper arms and trunk. The NASA-TLX showed significant association between the side-standing position and high physical demand, effort, and frustration (p<0.05). The two-handed technique in the side-standing position required more effort than the one-handed (p<0.05). No difference in operative time or complication rate was demonstrated among the four procedures. The two-handed/between-standing method was chosen as the best procedure to teach and standardize. CONCLUSIONS: Laparoscopic cholecystectomy poses a risk of physical injury to the surgeon. As LC is currently commonly performed in the United States, the left side-standing position may lead to increased physical demand and effort, resulting in ergonomically unsound conditions for the surgeon. Though further investigations should be conducted, adopting the between-standing position deserves serious consideration as it may be the best short-term ergonomic alternative.

Advanced Modular Manikin and Surgical Team Experience During a Trauma Simulation: Results of a Single-Blinded Randomized Trial.

BACKGROUND: Our aim was assess whether an integrated Advanced Modular Manikin (AMM) provides improved participant experience compared with use of peripheral simulators alone during a standardized trauma team scenario. Simulation-based team training has been shown to improve team performance. To address limitations of existing manikin simulators, the AMM platform was created that enables interconnectedness, interoperability, and integration of multiple simulators ("peripherals") into an adaptable, comprehensive training system. METHODS: A randomized single-blinded, crossover study with 2 conditions was used to assess learner experience differences when using the integrated AMM platform vs peripheral simulators. First responders, anesthesiologists, and surgeons rated their experience and workload with the conditions in a 3-scene standardized trauma scenario. Participant ratings were compared and focus groups conducted to obtain insight into participant experience. RESULTS: Fourteen teams (n = 42) participated. Team experience ratings were higher for the integrated AMM condition compared with peripherals (Cohen's d = .25, p = 0.016). Participant experience varied by background with surgeons and first responders rating their experience significantly higher compared with anesthesiologists (p < 0.001). Higher workload ratings were observed with the integrated AMM condition (Cohen's d = .35, p = 0.014) driven primarily by anesthesiologist ratings. Focus groups revealed that participants preferred the integrated AMM condition based on its increased realism, physiologic responsiveness, and feedback provided on their interventions. CONCLUSIONS: This first comprehensive evaluation suggests that integration with the AMM platform provides benefits over individual peripheral simulators and has the potential to expand simulation-based learning opportunities and enhance learner experience, especially for surgeons.

Joint-specific disruption of control during arm movements in Parkinson's disease.

The leading joint hypothesis (LJH) suggests distinct types of control (leading and subordinate) at different joints during multi-joint movements. Taking into account specific features of movements in Parkinson's disease (PD), the LJH predicts distinct effect of PD on control of leading and subordinate joints: impaired interaction torque (INT) regulation should be emphasized at the subordinate joints, and impaired generation of muscle torque (MUS) magnitude should be more pronounced at the leading joint. This prediction was tested by studying three tasks of horizontal shoulder-elbow movements in PD patients and age-matched controls: cyclic line drawing, cyclic point-to-point, and discrete pointing movements. Each task included movements in different directions, providing both shoulder-lead and elbow-lead control patterns. Torque analysis supported the prediction, specifically for Tasks 2 and 3 in which movement targets were chosen to emphasize the shoulder- and elbow-lead control patterns. Patients did not exploit INT for motion generation as successfully as controls did, but only at the subordinate joint. Underproduction of MUS by PD patients was more apparent at the leading than subordinate joint. The results support joint-specific effect of PD on movement control. They also suggest that dyscoordination of joint motions in PD stems predominantly from impaired control of subordinate joints, while bradykinesia is associated more with control of the leading than subordinate joint. Possible contribution of the revealed impairments in joint control to some other movement features in PD is discussed. The study demonstrates the efficiency of the LJH application for revealing changes in joint control caused by motor disorders.

Submovements during pointing movements in Parkinson's disease.

Velocity irregularities frequently observed during deceleration of arm movements have usually been interpreted as corrective submovements that improve motion accuracy. This hypothesis is re-examined here in application to movements of Parkinson's disease (PD) patients in which submovements are specifically frequent. Pointing movements in patients and age-matched controls to large and small targets in three movement modes were studied. The modes were discrete (stop on the target), continuous (reverse on the target), and passing (stop after crossing the target). Two types of submovements were distinguished, gross and fine. In both groups, gross submovements were more frequent during the discrete and passing than continuous mode, specifically for large targets. This suggested that gross submovements were fluctuations accompanying motion termination (stabilization at the target) that was included in discrete and passing but not continuous movements. Gross submovements were specifically frequent in patients, suggesting that PD causes deficiency in smooth motion termination. Although in both groups fine submovements were more frequent for small than large targets, this relation was also observed in passing movements after crossing the target, i.e., when no corrections were needed. This result, together with higher jerk of the entire trajectory found for smaller targets, indicates that fine submovements may also be not corrective adjustments but rather velocity fluctuations emerging due to low speed of movements to small targets. This interpretation is consistent with the recognized inability of PD patients to promptly change generated force as well as to quickly re-plan current motion. The results suggest a need to re-examine the traditional interpretation of submovements in PD and the related theory that the production of iterative submovements is a strategy used by patients to compensate for a decreased initial force pulse.

Ergonomic risk associated with assisting in minimally invasive surgery.

BACKGROUND: Given the physical risks associated with performing laparoscopic surgery, ergonomics to date has focused on the primary minimally invasive surgeon. Similar studies have not extended to other operating room staff. Simulation of the assistant's role as camera holder and retractor during a Nissen fundoplication allowed investigation of the ergonomic risks involved in these tasks. METHODS: Seven subjects performed camera navigation and retraction tasks using a box trainer on an operating room table that simulated an adult patient in low lithotomy position. Each subject stood on force plates at the simulated patient's left side. A laparoscope was introduced through a port into the training box with four 2-cm circles as rear-panel targets located in relation to the assistant as distal superior, proximal superior, distal inferior, and proximal inferior target effects. The subjects held the camera with their left hand, pointing it at a target. The task was to match the target to a circle overlaid on the monitor. Simultaneously, a grasper in the right hand grasped and pulled a panel-attached band. A minute signal moved the subject to the next target. Each trial had three four-target repetitions (phase effect). The subjects performed two separate trials: one while holding the camera from the top and one while holding it from the bottom (grip effect). A 4 x 3 x 2 (target x phase x grip) repeated-measures design provided statistics. Dividing the left force-plate vertical ground reaction forces (VGRF) by the total VGRF from both plates provided a weight-loading ratio (WLR). RESULTS: The WLR significantly increased (p < 0.005) with proximal targets (2 by 80% and 4 by 79%). The WLR decreased 75%, 74%, and 71% over time. No difference existed between the grip strategies (grip effect, p > 0.5). CONCLUSIONS: A high-risk ergonomic situation is created by the assistant's left or caudal leg disproportionately bearing 70-80% of body weight over time. A distance increase between the camera head location and the camera holder increases ergonomic risk. The phase effect was interpreted as a compensatory rebalancing to reduce ergonomic risk. Ergonomic solutions minimizing ergonomic risks associated with laparoscopic assistance should be considered.

Segmenting and classifying activities in robot-assisted surgery with recurrent neural networks.

PURPOSE: Automatically segmenting and classifying surgical activities is an important prerequisite to providing automated, targeted assessment and feedback during surgical training. Prior work has focused almost exclusively on recognizing gestures, or short, atomic units of activity such as pushing needle through tissue, whereas we also focus on recognizing higher-level maneuvers, such as suture throw. Maneuvers exhibit more complexity and variability than the gestures from which they are composed, however working at this granularity has the benefit of being consistent with existing training curricula. METHODS: Prior work has focused on hidden Markov model and conditional-random-field-based methods, which typically leverage unary terms that are local in time and linear in model parameters. Because maneuvers are governed by long-term, nonlinear dynamics, we argue that the more expressive unary terms offered by recurrent neural networks (RNNs) are better suited for this task. Four RNN architectures are compared for recognizing activities from kinematics: simple RNNs, long short-term memory, gated recurrent units, and mixed history RNNs. We report performance in terms of error rate and edit distance, and we use a functional analysis-of-variance framework to assess hyperparameter sensitivity for each architecture. RESULTS: We obtain state-of-the-art performance for both maneuver recognition from kinematics (4 maneuvers; error rate of [Formula: see text]; normalized edit distance of [Formula: see text]) and gesture recognition from kinematics (10 gestures; error rate of [Formula: see text]; normalized edit distance of [Formula: see text]). CONCLUSIONS: Automated maneuver recognition is feasible with RNNs, an exciting result which offers the opportunity to provide targeted assessment and feedback at a higher level of granularity. In addition, we show that multiple hyperparameters are important for achieving good performance, and our hyperparameter analysis serves to aid future work in RNN-based activity recognition.

Development of a more robust tool for postural stability analysis of laparoscopic surgeons.

BACKGROUND: Physical difficulties experienced by surgeons performing minimally invasive surgery (MIS) are being given extensive attention by ergonomic researchers. Postural stability, not commonly addressed, is our prime focus. Center of pressure (COP) alone is used in the few existing postural stability studies. Using COP, we previously correlated postural stability to instrument type, task difficulty, and skill level. This study, including center of mass (COM), sway area analysis, and what we uniquely term postural stability demand (PSD), extends our investigation. METHODS: Six surgeons from different experience levels were recruited to complete three fundamentals of laparoscopy (FLS(TM)) tasks. Standing on two force plates, participants performed each task as a motion capture system recorded body movements. An ellipse was created for sway area analysis of COP, the point where the ground reaction force was located, and COM, the point at which body mass was concentrated. PSD was defined as the mean distance between the COP and COM locations in the anterior-posterior (A-P) or medial-lateral (M-L) directions. Postural parameters and performance time were correlated. RESULTS: COM and COP sway areas positively correlated with pegboard transfer performance time (r = 0.928, p < 0.05; r = 0.864, p < 0.05) and also with circle-cutting performance time (r = 0.858, p < 0.05; r = 0.779, p = 0.06). However, COM and COP sway areas negatively correlated with endo-loop placement performance time (r = -0.925, p < 0.05; r = -0.935, p < 0.05). These results indicate unique postural controls based on skill level. During all tasks, PSD in the A-P direction strongly correlated with performance time (r = 0.829, p < 0.05; r = 0.913, p < 0.05; r = 0.880, p < 0.05), indicating that less-skilled participants experienced increased postural demands. CONCLUSIONS: This study demonstrated that variance in postural adjustments, as evidenced by sway area analysis, correlate to skill level and individual task. Strong correlation between PSD and performance time shows potential as a predictor of skill levels. Combining COM, COP, and PSD data produces a more robust analytic tool for identifying postural adjustments that can be correlated with skill level.

Origins of submovements during pointing movements.

Submovements that are frequently observed in the final portion of pointing movements have traditionally been viewed as pointing accuracy adjustments. Here we re-examine this long-lasting interpretation by developing evidence that many of submovements may be non-corrective fluctuations arising from various sources of motor output variability. In particular, non-corrective submovements may emerge during motion termination and during motion of low speed. The contribution of these factors and the factor of accuracy regulation in submovement production is investigated here by manipulating movement mode (discrete, reciprocal, and passing) and target size (small and large). The three modes provided different temporal combinations of accuracy regulation and motion termination, thus allowing us to disentangle submovements associated with each factor. The target size manipulations further emphasized the role of accuracy regulation and provided variations in movement speed. Gross and fine submovements were distinguished based on the degree of perturbation of smooth motion. It was found that gross submovements were predominantly related to motion termination and not to pointing accuracy regulation. Although fine submovements were more frequent during movements to small than to large targets, other results show that they may also be not corrective submovements but rather motion fluctuations attributed to decreases in movement speed accompanying decreases in target size. Together, the findings challenge the traditional interpretation, suggesting that the majority of submovements are fluctuations emerging from mechanical and neural sources of motion variability. The implications of the findings for the mechanisms responsible for accurate target achievement are discussed.

Origins of submovements in movements of elderly adults.

BACKGROUND: Slowness is a well-recognized feature of movements in aging. One of the possible reasons for slowness suggested by previous research is production of corrective submovements that compensate for shortened primary submovement to the target. Here, we re-examine this traditional interpretation and argue that the majority of submovements in older adults may be a consequence rather than the cause of slowness. METHODS: Pointing movements in young and older adults were recorded. Conditions for submovement emergence were manipulated by using small and large targets and three movement modes: discrete (required stopping on the target), reciprocal (required reversal on the target), and passing (required crossing the target and stopping after that). Movements were parsed into a primary and secondary submovement based on zero-crossings of velocity (type 1 submovements), acceleration (type 2 submovements), and jerk (type 3 submovements). In the passing mode, secondary submovements were analyzed only after crossing the target to exclude that they were accuracy adjustments. RESULTS: Consistent with previous research, the primary submovement was shortened and total secondary submovement incidence was increased in older adults. However, comparisons across conditions suggested that many submovements were non-corrective in both groups. Type 1 submovements were non-corrective because they were more frequent for large than small targets. They predominantly emerged due to arm stabilization and energy dissipation during motion termination in the discrete and passing mode. Although type 2 and 3 submovements were more frequent for small than large targets, this trend was also observed in the passing mode, suggesting that many of these submovements were non-corrective. Rather, they could have been velocity fluctuations associated predominantly with low speed of movements to small targets. CONCLUSION: The results question the traditional interpretation of frequent submovements in older adults as corrective adjustments. Rather, the increased incidence of submovements in older adults is directly related to low movement speed observed in aging, whereas the relationship between submovement incidence and target size is a result of speed-accuracy trade-off. Aging-related declines in muscular control that may contribute to the disproportional increases in submovement incidence during slow movements of older adults are discussed.