Glovebox Workers’ Range of Motion in Three Gloveports
LA-UR-18-26972
THESIS
Presented in Partial Fulfillment of the Requirements for the Degree Master of Science in the
Graduate School of the Ohio State University
By
Alaina Preddie, B.S.
Graduate Program in Industrial and Systems Engineering
The Ohio State University
2019
Master’s Thesis Committee:
Dr. Carolyn M. Sommerich, Advisor
Dr. Steven A. Lavender
Cindy M. Lawton
Copyright by
Alaina Preddie
2019
Abstract
Introduction. To date, there is no documented data on the differences in range of motion between gloveport types nor worker preference. The information gathered through this study provides a quantitative comparison between three gloveport shapes and orientations (round, vertical oval, and 45° oval) as well as worker ratings and preferences.
Methods. Thirty-five experienced glovebox workers at Los Alamos National Laboratory were recruited to participate in this study. They performed two reach tasks to assess reach distance in the three ports and rated ease and/or difficulty of working in each port. Finally, the participants were asked to rate which port they most and least preferred.
Results. Vertical oval gloveports provided the greatest overall reach distances when compared to both the round and 45° oval gloveports. Most participants rated the vertical oval gloveports easiest to work in and selected them as their preferred gloveport.
Conclusions. This study demonstrated the positive effects of vertical oval gloveports in glovebox design. The experienced glovebox workers that participated in this study both preferred working in the vertical oval gloveport and attained the greatest reach distance in comparison to the round and 45° oval gloveports. Future glovebox design should take this information into account along with the processes performed in the glovebox.
ii
For my grandmother, Josephine, for teaching me the value of faith, patience, and forgiveness.
iii Vita
June 2013 ………………………………………Brownsburg High School
2016 ……………………………....……………B.S. Psychological Sciences, Purdue University
2016 to 2017 …………………………………..NIOSH Traineeship Recipient, Department of
Integrated Systems Engineering, The Ohio State
University
2018 to present ……………………….………..Graduate Research Assistant, Los Alamos
National Laboratory
Publications
Wang, X., Bigelow, S., Seagren, K. E., Preddie, A. K., Wang, Z., Ardiyanto, A., ... & Lavender,
S. A. (2018). Re-thinking floor mat design from an ergonomics perspective: Can a two-
part mat system reduce biomechanical loads during normal mat handling tasks?. Applied
ergonomics, 72, 17-24.
Fields of Study
Major Field: Industrial and Systems Engineering
Human Factors & Ergonomics
iv Table of Contents
Abstract ...... ii
Vita ...... iv
List of Tables ...... vi
List of Figures ...... vii
Chapter 1: Introduction ...... 1
Chapter 2: Methods ...... 10
Chapter 3: Results ...... 21
Chapter 4: Discussion ...... 44
Chapter 5: Conclusion...... 53
References ...... 54
Appendix A: Consent Form ...... 56
Appendix B: Participant Information Sheet ...... 58
Appendix C: VAS rating questions...... 61
Appendix D: Preference Questions ...... 62
v List of Tables
Table 1. Average resultant reach distances for hook hold condition, in inches, for the one-hand ring placement task by gloveport shape and direction...... 24
Table 2. Average horizontal reach distances from origin for hook hold condition, in inches, for the one-hand ring placement task by gloveport shape and direction...... 25
Table 3. Average vertical reach distances from origin for hook hold condition, in inches, for the one-hand ring placement task by gloveport shape and direction...... 26
Table 4. Average resultant reach distances for no hook hold condition, in inches, for the one- hand ring placement task by gloveport shape and direction...... 29
Table 5. Average horizontal reach distances from origin for no hook hold condition, in inches, for the one-hand ring placement task by gloveport shape and direction...... 30
Table 6. Average vertical reach distances from origin for no hook hold condition, in inches, for the one-hand ring placement task by gloveport shape and direction...... 31
Table 7. Results of a test of homogeneity of variance for the one-handed ring placement task.
Resulted in no significant differences between male and female variance...... 37
Table 8. Results of a test of homogeneity of variance for the two-hand lift and lower task.
Resulted in no significant differences between male and female variance...... 39
vi List of Figures
Figure 1. Glovebox workers in a glovebox. Image from Lawton & Grogin, 2004...... 1
Figure 2. Glovebox worker survey results demonstrating increased prevalence of symptom reporting with years of glovebox work experience (Lawton, 2013)...... 2
Figure 3. Round gloveports with 8 in. diameter...... 12
Figure 4. Vertical oval gloveports with minor axis of 7 in. and major axis of 11 in...... 13
Figure 5. 45° oval gloveports with minor axis of 7 in. and major axis of 11 in...... 13
Figure 6. Gloveport stand setup with pegboard behind...... 15
Figure 7. Pegboard with sectioned reach regions...... 15
Figure 8. Session and task flowchart ...... 16
Figure 9. (a) One-Hand Ring Placement task, no hook held condition; (b) photograph depicting one hand ring placement task...... 18
Figure 10. Two-Hand Lift & Lower task ...... 19
Figure 11. Average resultant reach distance for the one-hand ring placement task, with hook held, by gloveport and direction. Asterisk indicates significance at the α = 0.05 level...... 27
Figure 12. Average resultant reach distance for the one-hand ring placement task, without hook held, by gloveport and direction. Asterisk indicates significance at the α = 0.05 level...... 32
Figure 13. Average reach distance for the two-hand lifting task by gloveport. Asterisks indicates significance at the α = 0.05 level...... 33
vii Figure 14. Average reach distance for the two-hand lowering task by gloveport. Asterisks indicates significance at the α = 0.05 level...... 35
Figure 15. Average VAS rating by gloveport. Asterisks indicates significance at the α = 0.05 level...... 41
Figure 16. Percentage of participants that selected each gloveport as “most preferred” to work in
...... 42
Figure 17. Percentage of participants that selected each gloveport as “least preferred” to work in.
...... 43
viii The study in this thesis was conducted at Los Alamos National Laboratory. In accordance with the Review and Release of Scientific and Technical Information policy, this document has undergone review and approval through and has been deemed unclassified. The assigned Los
Alamos–Unrestricted Release identification number is LA-UR-18-26972.
ix Chapter 1: Introduction
The American Glovebox Society (AGS) defines a glovebox as “a controlled environment work enclosure providing a primary barrier from the work area. Operations are performed through sealed gloved openings to protect the worker, the ambient environment, and/or the product” (AGS, 2007). These workstations are used in a variety of industries including nuclear, pharmaceutical, semiconductor, and biochemical. Figure 1 shows an example of two glovebox workers conducting tasks in a nuclear glovebox.
Figure 1. Glovebox workers in a glovebox. Image from Lawton & Grogin, 2004.
1 Figure 2 shows the results of a symptom survey of glovebox workers at Los Alamos
National Laboratory (LANL) from 2013. The frequency of glovebox workers reporting symptoms increases with years on the job and more than 50% of glovebox workers experience symptoms after 25 years (Lawton, 2013). As reported by Christman (2016), LANL “worker reporting symptoms after 1-2 hours of glovebox work are 22%; this grows to over 50% if glovebox work exceeds 3 hours a day.” Contact stress, restricted motion, and resulting shoulder injuries were listed as concerns (Christman, 2016). The amount of time that glovebox workers perform tasks in gloveboxes varies widely at LANL; however, all glovebox workers adhere to guidelines that prescribe working in the glovebox for short durations of time, then performing personal monitoring for radiation before doing any additional work.
Percentage of Workers Reporting Symptoms vs. Years as a Glovebox Worker
Figure 2. Glovebox worker survey results demonstrating increased prevalence of symptom
reporting with years of glovebox work experience (Lawton, 2013).
2 Gloveports are apertures on a glovebox that allow gloves to be secured to the glovebox.
In 2011, AGS published ergonomic guidelines for gloveboxes with detailed information on gloveport design. This guide advises considering options for gloveport height, shape, orientation, size, spacing, and type during the design process of a new glovebox (American Glovebox
Society, 2011). These guidelines provide a basis for gloveport selection based on tasks and processes; however, it is important to make selections carefully as gloveboxes are quite expensive to produce. For example, at LANL the total cost of a glovebox from design to installation is around $1 million, with the amount for just building being between $250,000 and
$300,000.
The current literature on glovebox ergonomics is quite limited. While some studies focus broadly on the ergonomic analysis of specific gloveboxes (McNair, 2006; Whitmore & Mount,
1995; Whitmore, McKay, & Mount, 1995), others have explored specific design elements such as the effect of gloveport height (Williams, 2006).
Several factors, when considered together, would suggest more research is needed on glovebox ergonomics: the high costs associated with work-related musculoskeletal injuries
(American Academy of Orthopaedic Surgeons, 2011), prevalence of symptom reporting in glovebox workers (Lawton, 2013), speculation on improvements suggested by prior research, and the lack of systematic research on specific aspects of glovebox design, including gloveport shape and orientation. Prior research on the ergonomic analysis of specific gloveboxes specifically suggests the use of alternative gloveport shapes (McNair, 2006; Whitmore, McKay,
& Mount, 1995).
This thesis aims to explore two aspects of glovebox design: gloveport shape and orientation. Three gloveports (round, vertical oval, and 45° oval) were compared based on reach
3 distance and preference. Thirty-five glovebox workers at LANL participated in a 30-minute session consisting of providing demographic information, performing two tasks in each of the three gloveports, and responding to four survey questions. The results of this study will provide glovebox designers information to assist with the selection of an appropriate gloveport shape and orientation. This information could be useful in various industries where gloveboxes are utilized.
1.1 Background
Gloveboxes are sealed workstations used to protect workers, the ambient environment, and/or the materials within the glovebox itself. A glovebox is used in a variety of industries. For example, the pharmaceutical industry will use gloveboxes to isolate materials to maintain chemical integrity. The semiconductor industry utilizes gloveboxes for anti-static properties and to provide a low humidity environment. In the nuclear industry, gloveboxes are used to prevent radiation exposure.
The basic components that comprise a glovebox are the shell, doors, windows, and gloveports. The shell of a glovebox is typically made of sheet metal and supports the other components. Doors are used to transfer materials in, out, and between gloveboxes. Windows allow a worker to view the interior of a glovebox. Gloveports allow protected access to the interior of the glovebox (AGS, 2007).
Within the US Department of Energy Laboratory complex, gloveboxes are used in various capacities. For example, Idaho National Laboratory uses gloveboxes in fuel fabrication, material inspection, metallurgical casting, manipulator repair, and other processes to protect employees from uranium radiation exposure (Idaho National Laboratory, n.d.). LANL performs chemical and metallurgical operations involving plutonium and other nuclear materials which
4 produce radiation exposure. This is easily contrasted with the pharmaceutical industry. The pharmaceutical industry will often utilize isolation gloveboxes to maintain the chemical integrity of the materials workers handle in processes (McNair, 2006).
1.2 Gloveports
Gloveports are the openings on a glovebox that allow protective gloves to be secured. In designing a glovebox, gloveport height, shape, orientation, size, and spacing should be considered (AGS, 2011). Gloveport centerline height describes the distance from the ground to center of the gloveport. Gloveport centerline spacing is the distance from center-to-center between two gloveports. The AGS Guideline for Glovebox Ergonomics has detailed recommendations for gloveport design. These guidelines include reference to anthropometry to base recommendations for design on several dimensions, including elbow height, shoulder height, and biacromial breadth.
1.2.1 Gloveport Design Recommendations
In general product design, ideally products should fit from the 5th percentile female to the 95th percentile male on any given anthropometric measurement. Gloveboxes are no exception. In order to allow a majority of workers to perform a variety of tasks, gloveboxes need to account for the diversity of anthropometry between people. These recommendations are already written for gloveport centerline height and spacing.
Recommendations for gloveport centerline height are based on workers’ elbow height, shoulder height, and the various aspects of the tasks performed in the glovebox (i.e. work surface height, working distance from glovebox window, etc.). AGS has recommendations of 44 to 48 in. centerline height for the pharmaceutical industry and others focused on fine motor tasks while
5 recommending 48 to 52 in. for the nuclear industry and others with emphasis on reaching. Forty- eight inches is the 5th percentile female shoulder height while 52 inches is the 50th percentile female and 5th percentile male shoulder height. Gloveport centerline spacing should be based on workers’ biacromial breadth with a recommended distance of 15 to 17.5 in. Fifteen inches is the
50th percentile male biacromial breadth and 17.5 in. is the 95th percentile male. This data is taken from Pheasant’s Bodyspace: Anthropometry, ergonomics and the design of work which references measurements of a general “Caucasian” population (AGS, 2011; Pheasant, 2005).
Gloveports are round- or oval-shaped in varying sizes. Oval gloveports can be oriented with the longer axis horizontal, vertical, or at an angle. The selected orientation should be based on the motions required to perform tasks in the glovebox. All recommendations for gloveport shape, size, and orientation are meant to give options that may decrease the limitation on workers’ range of motion (AGS, 2011).
Gloveports limit range of motion by presenting a physical barrier that workers cannot push past. Design choices on gloveports must be weighed against other design criteria such as visibility, shielding requirements, and window size (AGS, 2011). Having a large gloveport can affect worker visibility into the workstation. If the size of a gloveport encroaches on the glovebox window, workers will not be able to see as easily inside the workstation. This can be mitigated by using a larger window; however, this may lead to some issues of hazardous conditions: Using a large gloveport or glovebox window may allow workers to move more freely or see into the workstation, but also allow for greater exposure to hazards such as radiation, external contamination, and biological hazards.
6 1.3 Glovebox Work
Glovebox work can pose a variety of hazards. One such hazard is the risk of musculoskeletal injuries to the shoulders from repetitive tasks and cumulative trauma from working in and holding awkward postures. Some work in gloveboxes involves lifting and manipulating objects weighing 15 – 25 lbs through gloveports (Lawton, Weaver, Chan, &
Cournoyer, 2016). Studying the effects of current designs and alternative designs on worker biomechanics and task proficiency might identify better designs that, if adopted, would have the potential to reduce workers’ exposure to what is discovered to be problematic in the current designs.
1.4 Ergonomics Research
The published literature on glovebox ergonomics is very limited. Ergonomic evaluations of industry specific gloveboxes have been conducted on two space-flight gloveboxes and a pharmaceutical glovebox.
The U.S. National Aeronautics and Space Administration (NASA) performed assessments of the Spacelab glovebox and glovebox-like enclosure, the General Purpose
Workstation on space flight missions. In both studies, flight crews submitted survey responses and video analysis was conducted on the workstations. Both studies found that changes were needed for the gloveport interfaces (Whitmore & Mount, 1995; Whitmore, McKay, & Mount,
1995). The Spacelab glovebox study went a step further and proposed redesigns for further study. One of the designs incorporated oval gloveports “so both small and large operators can position their arms comfortably without exerting any force on the edges of the ports.” (Whitmore et. al, 1995).
7 In the assessment of a pharmaceutical glovebox, McNair (2006) identified criteria for ergonomic improvements. The criteria included recommendations for illumination and visual performance, window structure, gloveports, and centerlines. Most notable was the possibility of incorporating oval gloveports to allow workers with varying anthropometry to comfortably work in the glovebox.
Some work has been completed to attempt to remedy known issues with glovebox design.
Effects of gloveport height were examined by Williams (2006). In a small sample of 6 male college students the researchers measured shoulder and back stresses using electromyography
(EMG), at the upper and lower bound of the AGS recommended 48 to 52 in. gloveport height.
Although they found no statistically significant results, there were reduced ratings of shoulder discomfort and decreased EMG activity at the 48 in. height.
At LANL, a robust ergonomics program has resulted in several published studies. Two of these studies for example resulted in developing a patented glovebox glove and developing a standard for working platform height (Lawton, Land, & Oka, 2015; Van Cleave, Lawton, 2012).
Furthermore, a study on rotator cuff strength balance from LANL found that glovebox workers had abnormal rotator cuff strength ratios which is a predictor of symptoms. This research also recommends future research to assess methods of reducing workload on the shoulder in glovebox work.
1.5 Next Steps in the Study of Gloveboxes
These previous studies give further reason to explore specifics in gloveport shape and how this affects workers’ reach and range of motion as well as preferences. The study described in the following chapters was intended to gather data on experienced glovebox workers’ reach
8 and preference in three gloveport shapes and orientations. This information will aid in future gloveport selection during glovebox design.
9 Chapter 2: Methods
2.1 Study Design
This study was performed at Los Alamos National Laboratory (LANL) with experienced glovebox workers. Prior to data collection, pilot testing was done to test session timing and data collection methods. Workers were not incentivized to participate in this study and participated during their regular work hours. To receive management approval for worker participation, study sessions were limited to approximately 30 minutes. The limitations of the methodology due to this time restriction will be discussed in the Discussion chapter of this document.
The objective of this study was to determine which gloveport (round, vertical oval, and
45° oval) minimized reach limitations during different tasks. In a study session, participants performed two reach tasks, rated the gloveports on a Visual Analog Scale (VAS), and selected which gloveports they most and least preferred to work in. The reach tasks were not meant to directly simulate tasks performed in gloveboxes; instead, they were intended to obtain reach data in the directions glovebox workers would typically work.
The overall study design included one primary independent variable, gloveport shape/orientation (round, vertical oval, and 45° oval), and three dependent variables, which were reach distance, visual analog scale rating, and preference. The study employed mixed methods, gathering quantitative measures on reach distance and qualitative opinion data via survey questions.
10 The study underwent review and approval by the internal Human Subjects Research
Review Board (HSRRB) at LANL. Each participant was provided with a descriptive consent form, Human Subjects Bill of Rights, and description of risks of participation (Appendix A & B).
2.2 Participants
Thirty-five glovebox workers from LANL were recruited through email and announcements at Worker Safety and Security Team meetings and/or Glovebox Safety Team Meetings.
Participants completed study sessions by appointment and walk-in. A maximum of 50 subjects was approved for this study by the HSRRB.
Information on gender, dominant hand, years as a glovebox worker, past shoulder injury, anti-c glove size, cotton liner usage, and platform utilization was collected. Participants were provided with their selected anti-c glove size, a cotton glove liner if desired, and a 2”-, 4”-, or 6”- platform on which to stand based on their preference. Height, mid-upper arm circumference, and arm length was measured and recorded as possible covariates. Stature was measured from the floor to the top of a participant’s head. For data analysis, a separate variable was created which includes the height of the platform if used by a participant. Functional reach of participants was measured from midpoint of the shoulder to center of the fist. Average arm circumference of participants was measured at the midpoint of the bicep.
Workers were excluded from participation in this study if they did not have at least one year of glovebox experience or were experiencing any pain and/or injury that might be aggravated by participation in the study.
11 2.3 Materials and Methods
2.3.1 Apparatus
2.3.1.1 Gloveports and Gloves
Three pairs of gloveports were fabricated for this study at LANL. All ports were
constructed from clear acrylic and stainless steel. The round ports measured 8 in. in diameter
(Figure 3). The vertical oval ports had a minor axis of 7 in. and major axis of 11 in. oriented
vertically (Figure 4). The 45° oval ports had the same major/minor axes measurements as the
vertical oval gloveports, set on a 45° angle away from the vertical orientation with the top of the
ports pointed away from one another (Figure 5). The measurements of each gloveport were
predetermined as standard for the shape at LANL.
Figure 3. Round gloveports with 8 in. diameter.
12
Figure 4. Vertical oval gloveports with minor axis of 7 in. and major axis of 11 in.
Figure 5. 45° oval gloveports with minor axis of 7 in. and major axis of 11 in.
Chlorosulfunated-polyethylene rubber glovebox gloves size 9-¾ manufactured by
Honeywell International Inc. were fitted to all gloveports. These gloves were 30 mil thickness and 32 in. in length. Participants in this study were asked to wear anti-contamination gloves
(Trionic E-194) inside the glovebox gloves. An optional pair of cotton liners were offered to participants as well. The gloves worn by participants simulated the workers’ regular work conditions.
13 2.3.1.2 Gloveport stand setup
For this study, participants did not work in an actual glovebox. A rack constructed of
aluminum framing material (80/20, Inc., Columbia IN) was used to hold the gloveports at the
desired height and centerline distance (Figure 6). During testing, each pair of gloveports was
mounted on the rack with 52 in. centerline above the floor and 16.5 in. centerline between the
two matching ports, based on recommendations and LANL practices. A typical glovebox at
LANL has a 52 in. centerline above the floor and 18 in. centerline between gloveports. Vertical
gloveport spacing can range from 48 to 52 in. while horizontal centerline ranges from 15 to 18
in. with a nominal spacing of 16.5 in. (McNair, 2006; AGS, 2011).
A pegboard with 2.375 in. hooks was set 18 in. behind the gloveport stand. This distance
was determined as part of the maximum range at which glovebox tasks should be performed, as
cited in McNair (2006). This pegboard was sectioned off with eight colors of tape to distinguish
the regions participants would reach for in the later described tasks (Figure 7). The hooks were
1.5 in. apart vertically and horizontally. A coordinate system was labeled on the hooks to aid
data collection and converted into distances for analysis.
14
Figure 6. Gloveport stand setup with pegboard behind.
Figure 7. Pegboard with sectioned reach regions.
15 2.3.2 Tasks
Figure 8 depicts a flowchart of a study session. The tasks are described in more detail in
the following sections.
Figure 8. Session and task flowchart
2.3.2.1 One-Hand Ring Placement
Participants performed a one-hand ring placement task in all three gloveport
configurations. The purpose of this task was to obtain reach data in a full range of directions.
Participants placed small, metal rings with a 1.25 in. diameter in eight directions (up, up and
dominant side (i.e. lateral), dominant side, down and dominant side, down, down and medial (i.e.
non-dominant side), medial, and up and medial). Participants used their dominant hand to
perform this task, reaching as far as they could in each direction. To prevent torso twisting, 16 participants held onto a hook in the pegboard with their non-dominant hand. This hook was positioned at the center point of their non-dominant hand’s gloveport. This was performed for two trials per gloveport. Participants also performed this ring placement twice without holding onto the hook for two trials per gloveport in order to provide unrestricted reach data. For the “no hook” version of the task, participants were asked to keep their non-dominant arm fully in the gloveport but otherwise posture was not controlled. Figure 9a shows a visual representation of the one-hand ring placement task with the no hook held condition; Figure 9b provides a photograph of the task. Within each gloveport condition, the test order of the hook/no hook conditions were randomized for each participant.
17
(a) (b) Figure 9. (a) One-Hand Ring Placement task, no hook held condition; (b) photograph depicting
one hand ring placement task.
2.3.2.2 Two-Hand Lift and Lower
Participants were also asked to perform a two-handed canister lifting and lowering task in
all three gloveport configurations. The purpose of this task was to obtain reach data in a posture
commonly adopted during glovebox tasks, lifting or lowering objects with both hands. In this
task, participants lifted and lowered a metal canister with both hands as far upward and
downward as they could reach for one trial in each direction. In pilot studies prior to final data
collection, participants did not vary in their reach distances for this task in multiple trials. Due to
18 this and to reduce session time, only one trial was performed by each participant for this task.
The metal canister was empty and weighed 0.5 lbs. The dimensions of the canister were 6 in. height and 4 in. diameter. Figure 10 shows a visual representation of the two-hand lift and lower task.
Figure 10. Two-Hand Lift & Lower task
2.3.3 Survey
After completing the one-handed and two-handed tasks in each gloveport, participants rated their perception of ease or difficulty of working in the gloveport on a Visual Analog Scale
19 (VAS) with statements of “Imagine working in (gloveport), rate your ability to accomplish glovebox tasks” and anchors of “Very Difficult” and “Very Easy.” Lastly, participants rated which gloveport was the most and least preferred. An example of the VAS rating question and final questions can be found in Appendices C and D, respectively, of this document.
2.4 Analysis
All analysis was performed in SPSS statistical software (version 25, IBM). A repeated measures ANOVA with three independent variables (gloveport shape, reach direction, and hook condition) was performed for the reach distance data from the one-handed task. Data for the one- hand ring placement task was recorded for the medial and lateral directions with respect to each participant’s handedness. For example, the distance for a left-handed individual reaching to the left and a right-handed individual reaching to the right were both recorded and analyzed in the
“lateral direction” while a left-handed individual reaching to the right and a right-handed individual reaching to the left were both recorded and analyzed in the “medial direction.” A repeated measures ANOVA with two independent variables (gloveport shape and direction) was performed on the reach distance from the two-handed task and VAS ratings. The preference selections were tabulated and summarized. For all repeated measures ANOVAs, if the null hypothesis was rejected at the α-level of 0.05, meaning a difference was found between the measurements of each gloveport, a Bonferroni post hoc test was performed to determine which gloveports showed a significance difference.
An analysis of correlation was performed between demographic data, reach distances, lift distances, and lower distances collected in the study. This was done to assess the relationships between the reach data and demographic data collected in the study. Prior to data collection it was hypothesized that functional reach, and height including step platform if used would be
20 positively correlated with reach data while arm circumference and years of experience would have little to no correlation. Differences between men and women were expected to be present in the data.
Pearson’s correlations were calculated for functional reach, height, arm circumference, and years of experience as these are all continuous variables. A point-biserial correlation was calculated for gender as this is a categorical variable. As the number of females in the participant pool was small, Levene’s Test of Equal Variance was used to check if the equal variance assumption was violated.
21 Chapter 3: Results
3.1 Demographic Information
3.1.1 Recruitment
28 male and 7 female glovebox workers participated in this study for a total of 35 participants. Participants were predominantly right-handed (88%, 31 of 35), with three being left-handed, and one participant identifying as ambidextrous (this individual performed the one- hand task with the left hand). The average years of reported experience working in gloveboxes was 10.5 years (sd = 8.9). All participants had prior experience working in the round gloveports.
Thirteen participants had a previous shoulder injury, five on their left shoulder, seven on their right shoulder, and one injured both shoulders.
The average height of male participants, including step platform height if used, was 69.8 in.
(sd = 2.6). The average height of female participants, including step platform height if used, was
65.9 in. (sd = 4.1). Average functional reach of male participants was 25.6 in. (sd = 6.0). The average functional reach of female participants was 22.7 in. (sd = 2.3). The average arm circumference of male participants at the midpoint of the bicep was 13.5 in. (sd = 1.2). The average arm circumference of female participants at the midpoint of the bicep was 10.8 in. (sd =
0.9).
22 3.2 Reach Tasks
3.2.1 One-Hand Ring Placement
The results of the repeated measures ANOVA with three independent variables found significant interaction effects for shape*direction (p < 0.001), direction*hook (p = 0.001), and shape*direction*hook (p =0.01). Significant main effects of shape (p<0.001), direction
(p<0.001), and hook (p<0.001) support these interaction effects.
With Hook. Tables 1, 2, and 3 summarize the average resultant reach distances, horizontal component, and vertical component for the one-hand ring placement task while holding onto a hook with the non-dominant hand to prevent participants from turning their torso while reaching. A repeated measures ANOVA was conducted to determine statistically significant differences for each direction for the resultant reach distance (see Table 1). The directions for which the ANOVA resulted in a rejected null hypothesis, meaning that there were differences between the three gloveport shapes, were up (p < 0.001), up & lateral (p < 0.001), down & lateral (p < 0.001), down (p < 0.001), and up & medial (p < 0.001).
Pairwise comparison showed significant differences between the round and vertical oval gloveports for the up & lateral (p < 0.001), down & lateral (p = 0.03), and up & medial (p =
0.001) directions. For the comparison between round and 45° oval gloveports, a significant difference was found for the down (p = 0.03) direction. Pairwise comparison showed significant differences between the vertical oval and 45° oval gloveports for the up (p = 0.01), down & lateral (p = 0.01), and down (p = 0.003). Figure 11 shows a comparison for each gloveport shape by direction. Asterisks designate significant differences.
23 Reach Direction Up Up & Lateral Down & Down Down & Medial Up & Lateral Lateral Medial Medial Round 25.4 25.0 24.1 24.2 25.5 26.4 26.3 25.3 Gloveport (sd: 1.6) (sd: 1.2) (sd: 1.5) (sd: 1.6) (sd: 1.4) (sd: 1.7) (sd: 2.1) (sd: 1.3) Shape Vertical 25.7 26.1 24.1 24.8 25.7 26.3 26.2 26.4 Oval (sd: 1.4) (sd: 1.5) (sd: 1.7) (sd: 1.5) (sd: 1.3) (sd: 1.9) (sd: 2.3) (sd: 1.5) 45° Oval 24.8 25.1 24.1 23.7 24.8 26.0 25.7 25.6 (sd: 1.5) (sd: 1.3) (sd: 1.7) (sd: 2.3) (sd: 1.4) (sd: 1.6) (sd: 2.0) (sd: 1.4)
Table 1. Average resultant reach distances for hook hold condition, in inches, for the one-hand ring placement task by gloveport shape
and direction.
24 Reach Direction Up Up & Lateral Down & Down Down & Medial Up & Lateral Lateral Medial Medial Round 0.0 12.8 18.3 13.9 0.0 15.0 21.5 13.6 (sd: (sd: 1.2) (sd: 1.9) (sd: 1.3) (sd: 0.0) (sd: 1.2) (sd: 2.2) (sd: 2.1) 0.0) Gloveport Vertical 0.0 14.0 18.5 14.5 0.0 15.3 21.6 14.8 Shape Oval (sd: (sd: 1.8) (sd: 2.7) (sd: 1.3) (sd: 0.0) (sd: 1.0) (sd: 2.1) (sd: 2.1) 0.0) 45° Oval 0.0 12.7 18.3 13.6 0.0 14.8 20.9 14.6 (sd: (sd: 1.1) (sd: 2.2) (sd: 1.9) (sd: 0.0) (sd: 1.2) (sd: 1.9) (sd: 2.4) 0.0)
Table 2. Average horizontal reach distances from origin for hook hold condition, in inches, for the one-hand ring placement task by
gloveport shape and direction.
25 Reach Direction Up Up & Lateral Down & Down Down & Medial Up & Lateral Lateral Medial Medial Round 20.0 14.7 0.0 12.0 21.6 16.1 0.0 14.7 (sd: (sd: 1.1) (sd: 0.0) (sd: 1.8) (sd: 1.8) (sd: 1.4) (sd: 0.0) (sd: 1.4) 2.1) Gloveport Vertical 20.3 15.4 0.0 12.5 21.8 16.1 0.0 15.3 Shape Oval (sd: (sd: 1.1) (sd: 0.0) (sd: 1.6) (sd: 1.6) (sd: 1.6) (sd: 0.0) (sd: 1.3) 1.8) 45° Oval 19.2 14.9 0.0 11.6 20.7 15.6 0.0 14.7 (sd: (sd: 1.3) (sd: 0.0) (sd: 2.1) (sd: 1.8) (sd: 1.6) (sd: 0.0) (sd: 1.5) 1.9)
Table 3. Average vertical reach distances from origin for hook hold condition, in inches, for the one-hand ring placement task by
gloveport shape and direction.
26 * * * * * *
Figure 11. Average resultant reach distance for the one-hand ring placement task, with hook
held, by gloveport and direction. Asterisk indicates significance at the α = 0.05 level.
Without Hook. Tables 4, 5, and 6 display average resultant reach distances, horizontal component, and vertical component for the one-hand ring placement task without the hook being held. A repeated measures ANOVA was conducted to determine statistically significant differences for each direction for the resultant reach distance (see Table 4). The directions for which the ANOVA resulted in a rejected null hypothesis, meaning that there were differences
27 between the three gloveport shapes, were up (p < 0.001), down (p < 0.001), down & medial (p <
0.001), medial (p < 0.001), and up & medial (p < 0.001).
For the comparison between round and 45° oval gloveports, a significant difference was found for the down (p = 0.001), down & medial (p = 0.009), and medial (p < 0.001) directions.
Pairwise comparison showed significant differences between the vertical oval and 45° oval gloveports for the up (p < 0.001), medial (p = 0.04), and up & medial (p < 0.001) directions.
Figure 12 shows a comparison for each gloveport shape by direction. Asterisks designate significant differences.
28 Reach Direction Up Up & Lateral Down & Down Down & Medial Up & Lateral Lateral Medial Medial Round 25.8 25.3 24.4 24.9 26.1 27.0 27.2 25.7 Gloveport (sd: 1.3) (sd: 1.1) (sd: 1.6) (sd: 1.5) (sd: 1.2) (sd: 1.5) (sd: 2.1) (sd: 1.1) Shape Vertical 26.2 26.7 24.3 25.1 25.9 26.9 26.9 26.9 Oval (sd: 1.0) (sd: 1.5) (sd: 1.6) (sd: 1.6) (sd: 1.1) (sd: 1.6) (sd: 2.2) (sd: 1.5) 45° Oval 25.2 25.3 24.3 24.3 25.3 26.1 26.4 26.3 (sd: 1.4) (sd: 1.2) (sd: 1.5) (sd: 1.8) (sd: 1.3) (sd: 2.0) (sd: 1.8) (sd: 1.3)
Table 4. Average resultant reach distances for no hook hold condition, in inches, for the one-hand ring placement task by gloveport
shape and direction.
29 Reach Direction Up Up & Lateral Down & Down Down & Medial Up & Lateral Lateral Medial Medial Round 0.0 13.0 18.6 14.6 0.0 15.2 22.4 14.0 (sd: (sd: 1.2) (sd: 2.0) (sd: 1.3) (sd: 0.0) (sd: 1.2) (sd: 2.2) (sd: 2.6) 0.0) Gloveport Vertical 0.0 14.7 18.6 14.8 0.0 15.3 22.2 15.0 Shape Oval (sd: (sd: 1.6) (sd: 2.1) (sd: 1.2) (sd: 0.0) (sd: 1.1) (sd: 2.1) (sd: 1.6) 0.0) 45° Oval 0.0 13.1 18.5 14.1 0.0 (sd: 14.9 21.3 14.5 (sd: (sd: 1.2) (sd: 1.9) (sd: 1.6) 0.0) (sd: 1.1) (sd: 2.0) (sd: 1.2) 0.0)
Table 5. Average horizontal reach distances from origin for no hook hold condition, in inches, for the one-hand ring placement task
by gloveport shape and direction.
30 Reach Direction Up Up & Lateral Down & Down Down & Medial Up & Lateral Lateral Medial Medial Round 20.5 15.0 0.0 12.6 22.3 16.1 0.0 15.5 (sd: (sd: 0.9) (sd: 0.0) (sd: 1.5) (sd: 1.5) (sd: 1.4) (sd: 0.0) (sd: 2.3) 1.6) Gloveport Vertical 21.0 15.9 0.0 12.9 22.0 16.1 0.0 15.9 Shape Oval (sd: (sd: 1.3) (sd: 0.0) (sd: 1.5) (sd: 1.4) (sd: 1.4) (sd: 0.0) (sd: 1.3) 1.2) 45° Oval 19.8 15.0 0.0 12.1 21.2 15.7 0.0 15.3 (sd: (sd: 1.1) (sd: 0.0) (sd: 1.9) (sd: 1.6) (sd: 1.4) (sd: 0.0) (sd: 1.2) 1.7)
Table 6. Average vertical reach distances from origin for no hook hold condition, in inches, for the one-hand ring placement task by
gloveport shape and direction.
31 * * * * * *
Figure 12. Average resultant reach distance for the one-hand ring placement task, without hook
held, by gloveport and direction. Asterisk indicates significance at the α = 0.05 level.
3.2.2 Two-Hand Canister Lift and Lower
3.2.2.1 Lifting task
The average two-handed lifting reach distance in the round gloveport was 23.8 in (sd =
1.2). The average two-hand lifting reach distance in the vertical oval gloveport was 24.4 in (sd =
1.0). The average two-hand lifting reach distance in the 45° oval gloveport was 23.5 in (sd =
1.0). The one-way ANOVA shows significantly different lifting reach distances between the 32 vertical vs. round ports and vertical vs. 45° oval ports. The vertical oval gloveports had the greatest reach distance when compared to both the round (p = 0.01) and 45° oval gloveports (p <
0.001). Figure 13 shows a comparison of lift distances for each gloveport shape. Asterisks designate significant differences.
* *
Figure 13. Average reach distance for the two-hand lifting task by gloveport. Asterisks indicates
significance at the α = 0.05 level.
33 3.2.2.2 Lowering task
The average two-hand lowering reach distance in the round gloveport was 24.8 in (sd =
1.6). The average two-hand lowering reach distance in the vertical oval gloveport was 25.7 in (sd
= 1.2). The average two-hand lowering reach distance in the 45° oval gloveport was 25.3 in (sd =
1.3). The one-way ANOVA analysis rejects the null hypothesis of the test (p = 0.001). Pairwise
comparison using the Bonferroni post-hoc test shows significantly different lowering reach
distances between the round and vertical gloveports. The vertical oval gloveport had the greatest
lowering distance of all three ports; however, it was only significantly greater when compared to
the round gloveport (p = 0.002). Figure 14 shows a comparison of lift distances for each
gloveport shape. Asterisks designate significant differences.
34 *
Figure 14. Average reach distance for the two-hand lowering task by gloveport. Asterisks
indicates significance at the α = 0.05 level.
3.3 Correlations
An investigation of correlation was performed for the demographic information: gender, years of experience, functional reach, arm circumference, and height accounting for platform use. Significant correlations will be reported with their correlation coefficient (r) and significance value (p).
35 One-Hand Ring Placement Task. For the round gloveport and hook held condition, a significant relationship was found between reach distances achieved in this task and functional reach (r = 0.40, p = 0.017), and between reach distance and participant height accounting for platform use (r = 0.40, p = 0.021). These results indicate that there is a modest positive correlation between reach distance in the round gloveport with the hook held with the non- dominant hand and functional reach and reach distance and height accounting for platform use.
For the round gloveport and no hook held condition, a significant relationship was found between reach distance and functional reach (r = 0.34, p = 0.017), and between reach distance and height accounting for platform use (r = 0.35, p = 0.046). These results indicate that there is a modest positive correlation between reach distance in the round gloveport in the no hook held condition and functional reach and reach distance and height accounting for platform use.
For the vertical oval gloveport and hook held condition, a significant relationship was found between this task and reach distance and height accounting for platform use (r = 0.36, p =
0.043). This result indicates that there is a modest positive correlation between reach distance in the vertical oval gloveport with the hook held with the non-dominant hand and height accounting for platform use.
For the vertical oval gloveport and no hook held condition, a significant relationship was found between reach distance and height accounting for platform use (r = 0.36, p = 0.043). This result indicates that there is a modest positive correlation between reach distance in the vertical oval gloveport in the no hook held condition and functional reach and reach distance and height accounting for platform use.
Prior to running the point-biserial correlation analysis, the variance for gender were examined for equality. Table 7 displays the results of the significance testing for homogeneity of
36 variance for gender and the one-hand ring placement task conditions. All the values are not significant, meaning the variance for males and females is not unequal and the results of the point-biserial correlation analysis are valid.
Condition Significance
Round, hook held p = 0.393
Round, no hook held p = 0.393
Vertical oval, hook held p = 0.417
Vertical oval, no hook held p = 0.811
45° oval, hook held p = 0.604
45° oval, no hook held p = 0.309
Table 7. Results of a test of homogeneity of variance for the one-handed ring placement task.
Resulted in no significant differences between male and female variance.
Two conditions resulted in gender having a significant correlation with reach distance in the one-handed task. Gender and reach distance in the round gloveport with hook held (r = -
0.348, p = 0.040) were correlated meaning gender accounted for 12.1% of the variability of reach distance in this condition. Gender and reach distance in the vertical oval gloveport with hook held (r = -0.434, p = 0.009) were correlated meaning gender accounted for 18.8% of the
37 variability of reach distance in this condition. For analysis, gender was coded as male = 0 and female = 1. This designation explains the negative correlation.
There were no significant correlations found between reach distance and the anthropometric or the demographic data for the 45° oval gloveport.
Two-Hand Lift and Lower Task. Significant relationships were found between the vertical oval gloveport lift distance and functional reach (p = 0.51, r = 0.002) and between vertical oval gloveport lift distance and arm circumference (p = 0.44, r = 0.009). These results indicate that there is a moderate positive correlation between functional reach and lift distance and arm circumference and lift distance in the vertical oval gloveport. This counterintuitive relationship between arm circumference and lift distance will be further discussed in the next chapter.
For the 45° oval gloveport lift distance a significant correlation was found between lift distance and arm circumference (p = 0.49, r = 0.003). This result indicates that there is a moderate positive correlation between arm circumference and lift distance in the 45° oval gloveport.
Similar to the one-handed task, the variance for each gender was examined for equality for the two-handed task. Table 8 displays the results of the significance testing for homogeneity of variance for gender and the two-hand lift and lower task conditions. All the values are not significant, meaning the variance for males and females is not unequal and the results of the point-biserial correlation analysis are valid.
38 Condition Significance
Round, lift p = 0.565
Round, lower p = 0.292
Vertical oval, lift p = 0.755
Vertical oval, lower p = 0.124
45° oval, lift p = 0.302
45° oval, lower p = 0.630
Table 8. Results of a test of homogeneity of variance for the two-hand lift and lower task.
Resulted in no significant differences between male and female variance.
Gender and lift distance in the vertical oval gloveport (r = -0.461, p = 0.005) were correlated meaning gender accounted for 21.3% of the variability of lift distance in this condition. Gender and lift distance in the 45° oval gloveport (r = -0.578, p < 0.001) were correlated meaning gender accounted for 33.4% of the variability of lift distance in this condition. For analysis, gender was coded as male = 0 and female = 1. This designation explains the negative correlation.
There were no significant correlations found between the reach distances and the demographic data or anthropometric data for the round gloveport lifting or lowering conditions.
39 3.4 Ratings and Preference
3.4.1 VAS Ratings
VAS ratings were measured to the nearest 0.1 cm. The average rating for the round gloveport was 6.2. The average rating for the vertical oval gloveport was 7.5. The average rating for the 45° oval gloveport was 6.1. A significant difference was found in the one-way ANOVA analysis and a pairwise comparison showed a significantly different rating between the vertical vs. round ports and vertical vs. 45° oval ports. The vertical oval gloveport had the highest VAS rating when compared to both the round (p =0.002) and 45° oval gloveports (p = 0.006). Figure
15 shows a comparison of VAS ratings for each gloveport shape. Asterisks designate significant differences.
40 * *
Figure 15. Average VAS rating by gloveport. Asterisks indicates significance at the α = 0.05
level.
3.4.2 Preference
Figure 16 shows the percentage of each gloveport selected as “most preferred gloveport to work in.” For “most preferred,” 6 of 35 participants (17 %) selected the round ports, 22 of 35 participants (63%) selected the vertical oval ports, and 7 of 35 participants (20%) selected the
45° oval ports. Figure 17 shows the percentage of each gloveport selected as “least preferred gloveport to work in.” For “least preferred,” 16 of 35 participants (47%) selected the round ports,
41 2 of 35 participants (5%) selected the vertical oval ports, and 17 of 35 participants (48%) selected the 45° oval ports.
Figure 16. Percentage of participants that selected each gloveport as “most preferred” to work in
42
Figure 17. Percentage of participants that selected each gloveport as “least preferred” to work in.
43 Chapter 4: Discussion
The goal of this study was to explore the effects of gloveport shape and orientation on reach distance and perceptions of experienced glovebox workers. In this section, the results of the study will be reviewed in the broader context of glovebox work. The participants’ informal comments recorded during sessions will be explored along with the study limitations. This chapter will conclude with suggestions for next steps in the research of glovebox design.
4.1 One-Hand Ring Placement Task
While it is important to take all reach directions into account for glovebox work, the vertical and lateral directions have implications for awkward postures. Lateral transfers through airlocks involve pushing against the edge of a gloveport to send an item to another glovebox.
Reaching laterally with a single hand while externally rotating the shoulder involves an awkward posture. Reaching upwards or downwards to access tall equipment, disposal of materials through the floor of a glovebox, and other tasks require glovebox workers to also push against the gloveport edges to reach different areas of a glovebox. A gloveport shape which maximizes the reach in these directions would be beneficial.
The practical significance of the results of the one-hand ring placement task should address any trepidation surrounding the adoption of oval gloveports. With a narrowed lateral portion of the port, it is easy to assume that worker motions may be restricted in the lateral directions in a vertical oval port. This is not the case, however. Where significant differences
44 occurred, the vertical oval gloveports provided the greatest reach distance among the three gloveports tested in the study. Any statistically significant increase in reach distance is important as a glovebox is a workstation with very limited accessibility. Participants were able to reach, on average, 0.4 in. farther than in the round gloveports and 0.7 in. farther than in the 45° oval gloveports. The results in each direction were more surprising.
In the medial and lateral directions (pure horizontal), there were no significant differences between gloveport conditions for the hook held condition, while the no hook condition revealed a significant result for the medial direction. In the up and down directions
(pure vertical), the vertical oval had the greatest reach distance between the three gloveports for the hook condition. However, the difference was only significant between vertical oval and 45° oval for the up direction. For the down direction, there was a significant difference between round and 45° oval, and vertical oval and 45° oval. The no hook condition has the same result for the up direction, a significant difference between the vertical oval and 45° oval, favoring the vertical oval. Looking at the down direction, however, shows the round gloveport having the greatest reach distance with a significant difference between round and 45° oval. It would seem the vertical oval gloveport should have the greatest down reach distance regardless of hook condition, but this is not the case. With the result not being significant between round and vertical oval in the down direction for the no hook condition, it may just be error due to worker familiarity, which will be discussed later. Hook condition was a simple main effect that supported the interaction effects of shape*direction, direction*hook, and shape*direction*hook.
Overall, participants were able to reach 0.5 in. further in the no hook held condition.
The overall greater reach distance in the vertical oval gloveports implies that range of motion was least hindered in this gloveport in comparison to the round and 45° oval gloveports.
45 The vertical oval showed particularly good reach distances for the diagonal directions with significantly greater distances in several directions in each hook condition. This implies the vertical oval may be a better general-use gloveport than the round gloveport.
4.2 Two-Hand Lift and Lower Task
The two-hand task looks at reaches that are typically done closer to the midline between gloveports. Depending on industry and process, these reaches may be done with an item of heavier weight than a one-handed task.
As noted earlier, any statistically significant increase in reach distance is important as a glovebox is a workstation with very limited accessibility. Participants had the greatest average lifting reach distance in the vertical oval gloveport, 0.5 in. greater than the round gloveport and
0.9 in. greater than the 45° oval gloveport. Participants also had the greatest average lowering reach distance in the vertical oval gloveport, 0.9 in. more than the round gloveport and 0.4 more than the 45° oval gloveport; however, only the comparison between the round and vertical oval was statistically significant. These results are not surprising with the major axis and orientation of the vertical oval gloveport allowing participants to move their arms higher in the port without pushing against the edge.
Looking at both the one-hand and two-hand reach tasks as a whole, the main effect of gloveport shape and orientation points to vertical oval as having the greatest overall reach. To reiterate this, participants were able to reach, on average, 0.4 in. farther in the vertical oval gloveports than in the round gloveports and 0.7 in. farther in the vertical oval gloveports than in the 45° offset oval gloveports. Participants were able to lift 0.5 in. higher in the vertical oval gloveports than the round gloveport and 0.9 in. higher in the vertical oval gloveports than the 45° oval gloveports. Participants could lower the canister 0.9 in. lower in the vertical oval gloveports
46 than the round gloveport and 0.4 lower in the vertical oval gloveports than the 45° oval gloveports.
4.3 Correlations
As stated in the methods chapter of this document, it was expected that functional reach, and height including step platform if used would be positively correlated with reach data while arm circumference and years of experience would have little to no correlation.
One-Hand Ring Placement Task. Results showed that years of experience and arm circumference did not have any correlation with the reach distances for the one-handed task.
Functional reach, height (including platform if used), and gender were significantly correlated with some of the reach distances for this task.
Functional reach was significantly and positively correlated with reach distance in both hook conditions for the round gloveport. This positive correlation simply put means that those with a longer functional reach also had a greater reach distance and conversely those with shorter functional reach had lower reach distances in this gloveport. This result was expected as it is logical that there is a relationship between a measure of arm length and reach ability. It is, however, unexpected that this only occurred in the round gloveport rather than all three gloveport shapes.
Height, accounting for platform use, was significantly and positively correlated with reach distance in both hook conditions for the round gloveport and both hook conditions for the vertical oval gloveport. Taller individuals, accounting for platform use, tended to have longer reach distances while shorter individuals tended to have shorter reach distances in these conditions. This result is not unexpected because there tends to be a positive correlation between stature and linear limb dimensions (Ahmed, 2013; Chawla and Khanna, 2015; Kamal and Yadav,
47 2016), although the use of platforms by only some of the participants would weaken the correlation between height and arm length in the current study.
Gender accounted for 12.1% of the variability of reach distance in the round gloveport with hook held. Gender accounted for 18.8% of the variability of reach distance in the vertical oval gloveport with hook held. The point-biserial correlation was negative, which corresponds to shorter height and shorter functional reach of females in this study. There were no significant correlations found between reach distance and the anthropometric or the demographic data for the 45° oval gloveport.
Two-Hand Lift and Lower Task. Results for the two-handed task showed that years of experience and height did not have any significant correlation with the lift or lower distances.
Arm circumference and functional reach had significant correlation with several conditions.
Arm circumference was significantly and positively correlated with vertical oval lift distance and 45° oval gloveport lift distance. Those with larger arm circumference typically had higher lift distances in these two conditions. Looking at the demographic information, males had overall greater height (accounting for platform use), greater arm circumference, and greater functional reach than females that participated. To confirm this, a post-hoc point-biserial correlation was conducted for gender and arm circumference. Gender accounted for 70.7% of the variability of arm circumference (r = -0.707, p < 0.001). This correlation was negative due to the coding of gender (male = 0 and female = 1). Taking this into account, a glovebox worker with a large arm circumference will be taller and have a longer reach, allowing them to lift to higher distance and reach to lower distances in the vertical oval gloveport before their arm contacts the edge of the gloveport.
48 Functional reach was significantly and positively correlated with vertical oval lift distance. This means that those with longer functional reach tended to have higher lift distances in the vertical oval gloveport. This is an expected result; however, it would have also been expected to be in other gloveports as well.
Gender accounted for 21.3% of the variability of lift distance in the vertical oval gloveport and 33.4% of the variability of lift distance in the 45° oval gloveport. The point- biserial correlation was negative, corresponding to shorter height and shorter functional reach of females in this study. There were no significant correlations found between the demographic data and reach distances for the round gloveport lifting or lowering condition.
4.4 VAS Ratings and Preference
The vertical oval was rated by the participants as the easiest gloveport through which to accomplish tasks. Furthermore, it was selected as the preferred gloveport above both the round and 45° oval gloveports. With the vertical oval having greater overall reach in one-handed tasks and two-handed tasks, it seems participants were able to account for this in their selections.
There was no statistically significant difference in the participants’ VAS ratings of the round and
45° oval gloveports. This was reflected in the choices of the participants “most preferred” (63% for vertical) and “least preferred” (47-48% for both round and 45° oval) gloveports. Given that the 45° oval gloveport produced lower reach distances than the round gloveport, one would expect participants to rate the 45° oval gloveport as less preferred than the round gloveport.
4.5 Informal Comments
Several participants expressed that they were familiar with working in the round gloveports and that may have impacted their reaches in each task as well as their preferences.
Participants expressed that they knew how comfortable they were pushing against the glove
49 attached to the gloveport as well as the gloveport edge. Many participants mentioned that they felt familiar with how far they could manipulate in the round gloveport. Participants may have been more cautious performing tasks in the oval gloveports. Being unfamiliar with any tension the glove presented in these ports and unsure of how far they could manipulate the glove without compromising it may have limited their reach. This familiarity with the round gloveports and unfamiliarity with the oval gloveports may partially explain participants having a greater reach in the down direction in the no hook held condition for the round gloveport.
Comments on restricted movement and limited mobility were also brought up frequently by participants. The 45° oval gloveport was most often noted as restricting. Reference to the possibility of bruising after extended use, pressure on different portions of the arm, and discomfort were mentioned for all three gloveports. This is expected from experience workers.
As the participants were experienced in glovebox work, they also brought up comments and questions unrelated to the study, but still important for gloveport design and selection. The topics they mentioned included: glove stretch, glove change methods, and visibility during work.
Each of these topics are influenced by gloveport shape and orientation selection. Each of these topics should be considered prior to gloveport shape and orientation selection to address any underlying concerns of adopting a different gloveport shape than typically used.
4.6 Study Limitations and Strengths
Limitations of this study include sample size, apparatus setup, task selection, platform use, and randomization. Initially, this study was approved to have up to fifty participants. Based on the data collection period and worker availability, only thirty-five workers participated. A larger sample size would have greater diversity in the anthropometry and be more reflective of the actual population of glovebox workers. While significant results were found among the tasks
50 in this study, a power analysis should have been performed on pilot data in order to determine an appropriate number of participants.
The apparatus was set up with the smallest distance vertically and horizontally between hooks in the pegboard; however, it may have been beneficial to use a board with smaller distances than 1.5 in. In the results chapter, average horizontal and vertical reach distances were reported in Tables 3, 4, 5, and 6 for the hook held and no hook held conditions respectively. This measurement is only reported to tenths place and is not very precise. Smaller distances would have allowed more precision in measuring reach distances.
The tasks chosen for participants to perform were not full simulations of glovebox tasks.
They were meant to give reach distances in the directions in which glovebox work may be required. Higher fidelity tasks may have produced different preference or VAS ratings among participants as they could be easier to compare to tasks participants perform in their day-to-day work.
Reviewing the methodology of this study, a better option would be to standardize platform use based on typical workstation. If a participant answered that they typically work with a platform of any height, they should have also used that size platform for this study rather than being allowed to perform the study tasks without a platform.
Task order was not entirely randomized in this study. Many aspects that may have influenced participant biases were randomized (gloveport order, hook condition order); however, randomizing task order and reach direction order would have been a better study design. A time restriction was placed on this study design. To receive management approval for worker participation, study sessions were limited to approximately 30 minutes. It was decided in early
51 pilot testing that leaving task order and reach direction order would limit the amount of instruction participants would need to complete tasks and stay within the time allotted.
The major strength of this study was that all participants were experienced glovebox workers at LANL. Had this study been performed in a university setting with participants who did not have experience as a glovebox worker, results could have been quite different. As mentioned previously, experienced glovebox workers know how hard they can push and how far they can reach in light of the discomfort they may experience if the contact with the gloveport is too severe. Inexperienced individuals would not have factored the knowledge of discomfort into their task performance.
4.7 Future Research
Further study on gloveport design should include studies with other gloveport shapes or orientations, such as a horizontal oval, and different gloveport centerline locations. A follow-up study in which participants perform tasks that are similar to actual glovebox tasks would also be beneficial to add to the knowledge of research surrounding gloveports.
52 Chapter 5: Conclusion
Glovebox work is known to cause workers discomfort and possible injury over time.
Although some research and publications have been provided to improve glovebox designs and give recommendations, some aspects of design are absent from published studies.
The present study found vertical oval gloveports provided greater reach distance than round or 45° oval gloveports in several directions in a one-handed and two-handed task. This implies that a vertical oval gloveport hinders workers’ range of motion less than the other two shapes for conditions tested in this study. Experienced workers surveyed in this study rated the vertical oval gloveports as easier to work in than the round or 45° oval gloveports. The vertical oval gloveport was also selected as the preferred gloveport to work in amongst the three. This information should be available to glovebox designers who may find it useful for future glovebox designs. Further research on gloveports should involve higher fidelity tasks and include other gloveport design such as centerline height and distance apart.
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55 Appendix A: Consent Form
56
57 Appendix B: Participant Information Sheet
58 59
60 Appendix C: VAS rating questions
61 Appendix D: Preference Questions
62