FYP Final Draft PDF

Shauna Walsh
12123951
BSc. Physiotherapy
2016

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The effects of different methods of load carriage on
posture, comfort and exertion levels: a comparison of two
different rucksack designs
Shauna Walsh
12123951
Supervisor: Dr. Karen McCreesh
PY4097/PY4008 Final Year Project
Word Count: 4,998
(Excluding: Title Pages, Declaration, Table of Contents
Acknowledgements, Abstract, Tables, Figures – plus table
and figure titles/footnotes, References and Appendices)

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I, the undersigned declare that this project which I am submitting is all my own work
and that the data presented is authentic.
_________________________ (Printed Name)
________________________ (Signature)
Date / /

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Table of Contents
Title page .........................................................................................................................1
Author's Declaration …………………………………………………….…………….3
Table of Contents …………………………………………………………………….....4
Acknowledgements .……………………………………………………………………6
Abstract .………………………………………………………………………………...8
1. Introduction ………………………………………………………………………….9
2. Methods……………………………………………………………………………...11
2.1 Design ……………………………………………………………………...11
2.2 Participants ………………………………………………………………....11
2.3 Outcome Measures ………………………………………………………....12
2.4 Procedure …………………………………………………………………...14
2.5 Postural Angle Synthesis …………………………………………………...17
2.6 Statistical Analysis ………………………………………………………....17
3. Results ………………………………………………………………………………17
3.1 Descriptive Data …………………………………………………………....17
3.2 Photograph Reliability ……………………………………………………...18
3.3 Key ResearchQuestions …………………………………………………....19
3.3.1 Question 1: Postural Change within Pack ……………………...…22
3.3.2 Question 2: Postural Change between Packs ………………….…24
3.4 Secondary Outcomes …………………………………………………….…27
3.4.1 Question 1: Discomfort and Exertion Changes within Packs …....27
3.4.2 Question 2: Discomfort and Exertion Changes between Packs ….29

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4. Discussion …………………………………………………………………………...30
4.1 Limitations …………………………………………………………………34
4.2 Implications for Practice …………………………………………………....34
5. Conclusion …………………………………………………………………………..35
6. References …………………………………………………………………………..37
7. Appendices ………………………………………………………………………….41
7.1 Appendix A - Postural Data Synthesis: Calculating CVA from Posture
Photographs ………………………………………………………………..41
7.2 Appendix B - Postural Data Synthesis: Calculating TFL from Posture
Photographs ………………………………………………………………..42
7.3 Appendix C - Written Informed Participant Consent …………………….....43
7.4 Appendix D - Mean NRS Scores for Backpack and Frontpack ………….....44
7.5 Appendix E - Distribution of Backpack BORG RPE …………………….....47
7.6 Appendix F - Distribution of Frontpack BORG RPE Scores …………….....48

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Acknowledgements
I would like to thank several important people.
Firstly, to my supervisor, Dr. Karen McCreesh. My sincerest thanks for your time,
expertise and guidance over the course of this project. To (soon to be Dr.) Eva Barrett
(MISCP) who I am forever grateful to for all your patience, time and help the past few
months. For always steering me in the right direction, helping me if I was stuck and
making time in your busy schedule. Thank you both for everything and for ensuring the
success of this project.
I express my sincerest gratitude to all of the participants who willingly
volunteered and offered time from their hectic schedules to partake in this research,
making this project possible. You all made the frontpack look good – think of me when
it takes off in the future!
To the CT technicians, in particular Trish Montgomery. Thank you for all of your
help in scheduling labs, organising and setting up equipment and for always keeping
everything immaculate.
To our year head, Dr. Susan Coote, and all the staff of the UL Physiotherapy
Department. Thank you for all your support and guidance over the past four years.
To my parents, Seán and Siobhán, for their unwavering support, encouragement,
help, advice, guidance and love over the past 22 years’ worth of endeavours, during this
degree and most recently during this project. Without you both I wouldn’t be who or
where I am today. Thank you for everything you’ve both done and continue to do for me,
and for providing me with the gift of my education and every opportunity to succeed in
life.

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To my siblings, Aoife, Jack, Hannah and Danny. Thank you for always giving me
a reason to look forward to travelling home at the weekend, for putting up with me when
grumpiness got the better of me and for always making me laugh with ye’re antics.
To the rest of my family for their continued support. In particular my Nanny,
Frances, for the holy medals, the endless cups of tea, and bags of goodies (for fear I wasn’t
being fed enough in Limerick) and for all the “chats” to Grandad, who I have no doubt
has always been looking after me from day one.
To the bunch of girls I’ve happily called housemates and friends. Thank you for
all of your support with everything, for always having someone to chat to over tea (or
chocolate!) and for sharing some of the best experiences life has to offer with me.
Finally to the people I’ve had the pleasure to call classmates over the past 4 years,
the wonderful Class of 2016. A massive thank you for making the past four years so
memorable and enjoyable. I wish you all continued success and happiness in the future
in everything you do.

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Abstract
The effects of different methods of load carriage on posture, comfort and exertion
levels: a comparison of two different rucksack designs
Background: Backpacks are typical amongst students of all ages, and have been
associated with back and neck pain in recent times. Most researchin the area has focused
on postural change in terms of backpack load and placement, primarily in children and
adolescents.
Objectives: 1. Investigate the effects that two methods of load carriage have on posture
while actively mobilising in adult university students. 2. Investigate their effects on
discomfort and exertion levels.
Methods: An observational study involving 22 students investigated the effects of a
backpack and frontpack on neck and trunk posture using digital photography, during a 10
minute treadmill walkwith packs containing 10% bodyweight. Secondary outcomes were
assessed using the Numerical Rating Scale for discomfort, and the BORG Rate of
Perceived Exertion scale for exertion.
Results: Results revealed both packs caused immediate and significant changes from
baseline, both when initially put on and after walking commenced (p<0.01). Overall the
backpack caused significantly greater and more negative changes in neck (p<0.05) and
trunk (p<0.01) posture than the frontpack. However the backpack caused significantly
less discomfort and exertion (p<0.05).
Conclusions: The most posture-effective method of loadcarriage remains uncertain. This
study queries the appropriateness of backpacks as the most common method, showing,
overall, frontpacks caused less negative postural changes. Further research, with larger
sample sizes and more rigorous methodology, is necessary.
Keywords: Backpack, Frontpack, Posture, Discomfort

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1. Introduction
The use of backpacks amongst students of all ages is the norm, with 90% reporting
backpack use worldwide (Reddy 2015). In Ireland, there were 544 696, 372 296 and
173 649 students in full-time first, second and third level education respectively in the
academic year 2014/15, indicating the substantial level of potential backpack-use (CSO
2015).
In normal standing posture the back muscles resist a trunk flexion moment. The
centre of gravity (COG) is located approximately in front of the lumbosacral joint. When
a loaded backpack is applied, the combined COG of the trunk and pack shifts backwards,
creating an extension moment (Pascoe et al 1997). As the COG moves compensations in
posture, in order to counteract the backpack weight, occur in the form of a forward trunk
lean to maintain functional movement and balance (Kistner et al 2012). Although
backpack weight is recommended to be 10-15% of bodyweight, students’ backpacks have
been recorded to weigh far more, which can impact the COG shift (Bauer and Frievalds
2009). Postural faults that persist can cause pain, discomfort and disability (Kendall et al
2005). As they regularly carry such weight it is no surprise that backpack usage has been
associated with back and neck pain in students (Grimmer and Williams 2000). Since a
history of back pain in youth is the strongest predictor of back pain in adulthood,
backpack design, usage and load have been of particular interest in research
(Chansirinukor et al 2001). With 83% of studies in this area published since 2000,
evidently the demand to study load carriage is rising (Golriz and Walker 2012).
Much recent research has focused on backpack load in children and adolescents
(Kistner et al 2013; Brackley et al 2009; Ramadan and Al-Shayea 2013). Kistner et al
(2012) investigated the postural changes associated with a 6 minute walk wearing a
backpack of 10%, 15% and 20% bodyweight in children aged 8-11. They found
immediate and statistically significant changes in neck position following immediate
placement of 15% and 20% bodyweight-load, and further changes across all loaded
conditions post-walk. Discomfort, primarily of the neck, was reported by 73% of subjects
after walking with 15% and 20% loads.

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A smaller volume of research, primarily in children, has focused on the method
of load carriage. A systematic review by Golriz and Walker (2012), identified three
studies where frontpacks induced less postural change than backpacks. They also found
there was limited evidence regarding the influence of frontpacks on variables such as
discomfort or pain.
Fair quality research investigated the trunk muscle activity of a doublepack,
frontpack and backpack in 19 adult college participants (Motmans et al 2006). While
overall the doublepack was best for posture, erector spinae activity levels significantly
decreased and increased while wearing a backpack and frontpack respectively.
To the author’s knowledge, only one other study has investigated these two packs
in terms of dynamic posture as the subject actively mobilises. All other research,
including the aforementioned studies, is limited to static postural angles or while the
subject stands stationary after dynamic movement. Fiolkowski et al (2006) applied video
analysis to determine postural angles in adult subjects as they walked with 10-15%
bodyweight-load on a treadmill. Reporting of this study’s methodology was poor, with
walk duration or when data was collected not stated. This study only investigated postural
change between pack loads and not in relation to the treadmill walk.
Therefore, the primary aim of this project was to investigate the effects that two
methods of load carriage – namely a backpack and frontpack, have on posture in adult
university students as the subject actively mobilised. This was measured by the
craniovertebral angle (CVA) and trunk forward lean (TFL). The secondary aim was to
investigate the effects that these two modes have on subjective levels of discomfort and
exertion. This research was undertaken using clinically accessible equipment and
measures, making it transferable to a clinical setting.

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2. Methods
Two methods of load carriage,and their effects on posture, exertion and discomfort, were
investigated. The 25L Sporthouse small day sack schoolbag served as both backpack and
frontpack to investigate their effects on the above outcomes. The straps of the bag were
adjusted individually so that the top of the bag was in line with the superior aspect of the
shoulder, similar to Kistner et al (2012). Each bag was loaded with 10% of the
individual’s body weight based on the recommendation by Kistner et al (2013). As
recommendations vary from 10-20%, the lower limit was chosen to attain a better insight
into the effect of pack type, instead of pack load, on posture.
The postural angles measured were examined by means of digital photography.
This non-invasive approach to measure the angles of interest is a reliable method of
obtaining quantitative clinical measurements of posture in the sagittal plane (van Niekerk
et al 2008; McEvoy and Grimmer 2005).
2.1 Design
This was a quantitative observational study. All subjects participated in two consecutive
sessions, testing both methods of load carriages, and thus acted as their own controls.
2.2 Participants
Participants were recruited from the University of Limerick Clinical Therapies
Department during October 2015 via word-of-mouth and information sessions. Any
interested, healthy, injury-free, university students were deemed eligible to participate
and were emailed by the researcher to schedule a convenient testing time. Subjects were
excluded if they met any of the criteria listed in Table 1. Approval was receivedfrom the
University of Limerick’s Faculty of Education and Health Sciences Research Ethics
Committee (2015_05_42_EHS)

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Table 1: Study Exclusion Criteria
Exclusion Criteria
 Any musculoskeletal or neurological condition that would be aggravated by
load carriage
 Currently on pain medication
 Non-fluent English speaker
 History of neck pain or scoliosis
 Any back/lower limb injury in the past 6 weeks
 Pregnant women
 Any known skin allergy to skin-adhesive substances
 Anyone below the age of 18
2.3 Outcome Measures
Two postural outcome measures were used.
Firstly, change in head position, relative to the trunk, in response to either pack was
assessed by measuring the CVA. This angle is formed from the intersection of a line from
the tragus of the ear to the spinous process of C7 and a horizontal reference line (Grimmer
et al 2002) (Figure 1). A smaller angle indicates a more forward head position (FHP).
This measure is highly reliable in analysing FHP using digital photographs. A reliability
study by van Niekerk et al (2008) found excellent correlation in angles between
photographs and low-dose radiographs (Interclass Correlation Coefficient (ICC) values
0.96-0.98).
Change in trunk position was assessed by measuring the TFL. This angle is
formed from the intersection of a vertical reference line with the one formed between the
greater trochanter to C7 (Kistner et al 2013). A smaller angle indicates a more forward
trunk position (FTP). For the purpose of this project this angle was interpreted as the
intersection of a vertical line with the one formed between the anterior superior iliac spine
(ASIS) and C7 (Figure 2). This project differs to previous research as the photographs

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gathering postural data were taken as the subject actively mobilised, not in a static
position. Therefore the ASIS, which remains relativelyconstant during gait, was chosen
to minimise the influence that gait would have on the data as the greater trochanter would
continuously move throughout the gait cycle. This measure has shown high reliabilityin
the measurement of FTP, with ICC values of 0.93-0.99 recorded (McEvoy and Grimmer
2005).
Figure 1: CVA Figure 2: FTL
Two secondary outcome measures were also used. The Numeric Rating Scale
(NRS) was used to measure discomfort. This scale ranges from 0-10, where 0 represented
“no discomfort” and 10 represented the “worstdiscomfort imaginable”. The NRS is more
practical than the Visual Analogue Scale as it is easier to understand and visualise,and is
equally as sensitive (Breiviket al 2008). The Borg Rate of PerceivedExertion (BorgRPE)
scale was used to measure exertion. This scale ranges from 6 (“no exertion”) to 20
(“maximal exertion”), and is a widelyused, valid measure of exercise intensity (Marsh et
al 2006).
Outcome measures were recorded at the five time points outlined in Figure 3.

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¥ Allowed an assessment of postural adaptation due to the pack alone
Figure 3: Outcome measure data collection points
2.4 Procedure
Testing occurred in October 2015, where eligible participants were invited to the testing
lab of the Physiotherapy Department, University of Limerick. Testing consisted of two
separate 30 minute sessions on the same day, all performed by the same researcher – a
final year Physiotherapy student, which standardised testing. Subjects were given a
detailed information leaflet outlining the study. They then completed the Physical
Activity Readiness-Questionnaire/PAR-Q, to ensure they were safe to participate in
exercise, and gave written consent.
Baseline measures were taken at the start of the first session – including height,
weight, age, and handedness. Adhesive visual markers were then placedon the right-hand
side of the body at the following locations: tragus of the ear, spinous process of C7 and
the ASIS. Subjects were prior-notified to wear suitable clothing to clearly expose the
visual markers. The order of pack to be tested per session was randomised – i.e. whether
the backpack or frontpack was tested first. Subjects chose from two concealed cards
coded to correspond to either backpack or frontpack. The bag was then loaded with 10%
of the individual’s bodyweight basedon baseline measurements, using free hand-weights.
1.
Unloaded
Standing
Data
collected
as subject
stands
normally
without
any pack
2. Loaded
Standing¥
Data
collected as
subject
stands
normally
once
allocated
pack
initially put
on
3. 0 minutes
Data
collected as
the subject
immediately
begins
walking
with the
pack - i.e. 0
minutes
4. 5 minutes
Data is
collected
after the
subject has
walked for 5
minutes on
the treadmill
5. 10
minutes
Data is
collected at
the end of
the treadmill
walk before
the subject
stops
walking

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To standardise photographs, subjects stood at an “L” marked on the floor with
masking tape, such that the lateral border of their right foot was in line with the long side
of tape and toes were in line with the short side. Digital photographs were taken in the
sagittal plane of the right side. A Fujifilm FinePix AX510 14 megapixel camera was
positioned in directline withthe individual 3 meters away, mounted on a tripodat a height
of 86cm from the ground. Subjects were asked to “stand normally”, looking straight
ahead. Photographs were taken in unloaded and loaded standing respectively.
Subsequently participants began the 10 minute treadmill walk. This duration was
chosen as comparable to the time taken for university students to walk between campus
buildings between lectures. Estimates of students’ walking times have been used as the
basis for the treadmill walk in previous research (Kistner et al 2013). Subjects were
instructed to increase the speed to a comfortable individual walking speed. The camera
was positioned 4 meters from the treadmill. Outcome measures were collected according
to Figure 3. At each time point, three photographs were taken to minimise the influence
of chance and to inform the reliability study discussed later. This concluded the first
session.
All participants returned one hour later for the second session. This aimed to
reduce the effects of any residual fatigue from the first session. The protocol outlined
above for session one was followed for session two, with subjects wearing the bag
randomised to be worn second and walking at the same treadmill speed used in session
one. Examples of each pack are given in Figures 4 and 5.

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Figure 4a: Backpack Figure 4b: Backpack during walk
Figure 5a: Frontpack Figure 5b: Frontpack during walk

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2.5 Postural Angle Synthesis
Once collected, photographs were analysed by the primary researcher using Paintshop
Pro X8 for Windows (Corel Corporation). The x and y plane coordinates for each
anatomical landmark of interest were obtained from each photograph. The CVA and TFL
angles were then manually calculated using basic trigonometry (Appendix A and B), and
transferred to Microsoft Excel for analysis.
2.6 Statistical Analysis
This study used a repeated-measures design. Statistical analysis procedures were
completed using SPSS software for Windows – version 22.0 (Chicago, IL, USA). Data
was considered normally distributed for Shapiro-Wilk values greater than 0.05. The
reliability analysis required ICC values to be calculated. Paired samples t-tests or
Wilcoxon Signed-Rank tests were used for parametric and non-parametric data
respectively to first test for significant differences in outcome measures within each pack
from start to finish of testing. The same tests were then used accordingly to assess for
significant differences in outcomes at the five time points between packs. Results were
considered significant if p<0.05.
3. Results
3.1 Descriptive Data
A convenience sample of 22 university students volunteered as participants, and met the
inclusion criteria. All subjects completed all data collection sessions. Since the same
subjects participated in both groups there were no differences between backpack and
frontpack groups at baseline. Baseline characteristics of all participants are described in
Table 2.1 and 2.2.

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Table 2.1: Baseline Characteristics of Study Population (n=22)
Characteristic % or Mean
(SD*)
%Male to %Female 18.2/81.8
Age (years) 22.45 (2.6)
Weight (kg) 66.55 (10.21)
Height (cm) 169.68 (6.84)
Handedness: %Right to %Left 81.8/18.2
First session: %Backpack to %Frontpack 50/50
Second session: %Backpack to %Frontpack 50/50
* SD = Standard Deviation, kg = kilograms, cm = centimetres,
Table 2.2: Baseline Characteristics of Study Population.
Treadmill
speed
(km/h)
Pack Weight
(kg)
(10%
bodyweight)
Distance
Mobilised (km)
Baseline CVA
(degrees)
Baseline TFL
(degrees)
B* F* B F B F
Mean
(SD**)
5.12 (0.78) 6.57 (1.03) 0.75
(0.08)
0.93
(0.25)
53.99
(4.54)
52.68
(5.48)
16.38
(2.07)
16.20
(2.00)
Min 4.0 5 0.69 0.75 44.74 43.15 12.84 10.81
Max 6.5 10 0.80 1.11 62.84 63.44 19.41 18.63
Range 2.5 5 0.11 0.36 18.12 20.28 6.57 7.82
* B = Backpack, F = Frontpack, ** SD = standard deviation, km = kilometres, km/h = kilometres per hour, kg = kilograms
3.2 Photograph Reliability
Three photographs were taken at each of the five data collection points for each subject.
A within-study reliability analysis was conducted to show there were no differences
between the three photographs. The CVA and TFL were calculated for all three

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photographs, at all time points, for the first five participants. Reliabilitybetween the first
and third photograph angle differences was identified through ICC values.
The ICC value for CVA and TFL angle between photograph one and photograph
three were 0.843 (95% Confidence Interval (CI) 0.724-0.911) and 0.951 (95% CI 0.914-
0.972) respectively. This justified the use of only the first photograph at each time point,
for each subject, for the remainder of the data analysis.
3.3 Key Research Questions
The primary aim of this research was to investigate the effects that a loaded backpack and
frontpack have on CVA and TFL in adult university students. Furthermore it aimed to
investigate the effects that these packs have on discomfort and exertion levels. To address
these aims, the data was analysed interms of the key researchquestions outlined in Figure
6. Mean CVA and TFL values for each pack are recorded in Table 3.

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Figure 6: Key Research Questions
Key Research
Questions
Primary Outcomes
1. Is there any change in
CVA/TFL from start to
finish of testing when
wearing either a
backpack or frontpack?
2. Which pack causes
more of a change in
CVA/TFL - backpack
or frontpack?
Secondary Outcomes
1. Is there any change in
discomfort/exertion from
start to finish of testing
when wearing either a
backpack or frontpack?
2. Which pack causes
more of a change in
discomfort/exertion -
backpack or
frontpack?

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Table 3.1: Mean CVA and TFL values for backpack condition
CVA (all values in degrees) Mean SD*
95% CI₩
Static Unloaded 53.99 4.54 51.98 – 56.01
Loaded 52.13 4.03 50.34 – 53.92
Dynamic 0 min 47.28 7.68 43.88 – 50.69
5 min 48.04 6.71 45.06 – 51.01
10 min 48.43 6.35 45.61 – 51.24
TFL (all values in degrees)
Static Unloaded 16.38 2.07 15.46 – 17.30
Loaded 12.99 2.55 11.86 – 14.13
Dynamic 0 min 8.02 3.31 6.56 – 9.49
5 min 7.52 3.28 6.07 – 8.98
10 min 8.30 2.94 7.00 – 9.60
* SD = Standard Deviation, ₩ CI = Confidence Interval
Table 3.2: Mean CVA and TFL values for frontpack condition
CVA (all values in degrees) Mean SD*
95% CI₩
Static Unloaded 52.68 5.48 50.25 – 55.12
Loaded 55.38 4.18 53.53 – 57.24
Dynamic 0 min 49.44 7.04 46.32 – 52.56
5 min 52.50 5.88 49.89 – 55.11
10 min 52.70 5.94 50.07 – 55.33
TFL (all values in degrees)
Static Unloaded 16.20 2.00 15.32 – 17.09
Loaded 18.76 2.03 17.86 – 19.66
Dynamic 0 min 15.62 2.88 14.35 – 16.90
5 min 15.73 2.84 14.47 – 16.98
10 min 15.78 2.77 14.55 – 17.01
* SD = Standard Deviation, ₩ CI = Confidence Interval

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3.3.1 Question 1: Postural Change within Pack
Both packs caused a change in CVA during testing (Figure 7). Mean changes and their
descriptive data are detailed in Appendix D.
The backpack caused an immediate and significant decrease in CVA (p=0.001)
when initial load was applied in standing, i.e. FHP increased. A further significant
decrease occurred when walking began at 0 minutes (p<0.0001). The CVA remained
lower compared to baseline and initial loading for the duration of the treadmill walk. No
further significant changes occurred between the remaining time points and there was no
significant difference in CVA between 0 and 10 minutes (p=0.405).
Conversely, the frontpack caused an immediate and significant increase in CVA
(p<0.001) when initial load was applied in standing, i.e. FHP decreased. Similar to the
backpack, a significant decrease occurred when walking began (p=0.006). As the subject
continued to walk the CVA returned to baseline level (p=0.012) at 5 minutes and
remained so for the remainder of the walk. There was a significant difference from 0 to
10 minutes (p=0.001), as FHP improved.

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*A decrease in CVA indicates an increase in forward head posture
Figure 7: CVA: Mean angle changes when carrying a loaded backpack and frontpack
Both packs also caused a change in TFL during testing (Figure 8).
Both packs caused an immediate and significant change in TFL when initial load
was appliedin standing – the backpack caused a decrease (p<0.0001), while the frontpack
caused an increase (p<0.0001), (i.e. a more backwards trunk lean). TFL significantly
decreased in both backpack and frontpack once the subject began walking, (p<0.0001)
and (p<0.001) respectively. There was no difference inTFL from 0 to 10 minutes in either
pack (p=0.438,p=0.756).
53.99
52.13
47.28
48.04 48.43
52.68
55.38
49.44
52.5 52.7
42
44
46
48
50
52
54
56
Unloaded Loaded 0 minutes 5 minutes 10 minutes
Angle(degrees)
Time
Change in CV Angle
CVA Backpack CVA Frontpack

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* A decrease in TFL indicates a more forward trunk posture
Figure 8: TFL: Mean angle changes when carrying a loaded backpack and frontpack
3.3.2 Question 2: Postural Change between Packs
Pairwise comparisons of CVA revealedsignificant differences between the backpack and
frontpack at three of the five time points, while differences were not significant at the
other two (Table 4).
The backpack caused a significant decrease in CVA when initial load was applied
compared to the frontpack. At 0 minutes, the backpack had a non-significantly lower
CVA than the frontpack. For the remainder of the walk backpacks caused a significantly
lower CVA at both 5 and 10 minutes when compared with the frontpack. Overall, the
backpack caused more change in CVA than the frontpack, with the backpack increasing
FHP more (Figure 9). Mean changes are detailed in Table 4.
16.38
12.99
8.02 7.52
8.3
16.2
18.76
15.62 15.73 15.78
0
2
4
6
8
10
12
14
16
18
20
Angle(degrees)
Time
Change in TFLAngle
TFL Backpack TFL Frontpack

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Table 4: Change between Backpack and Frontpack (CVA and TFL) between corresponding times when Frontpack values at the
corresponding times are subtracted from the Backpack values.
Change₩ Unloaded Change Loaded Change 0 min Change 5 min Change 10 min
Mean
(SD) **
(degrees)
p value Mean
(SD)
(degrees)
p value Mean
(SD)
(degrees)
p value Mean
(SD)
(degrees)
p value Mean
(SD)
(degrees)
p value
CVA -1.31¥
(7.43)
0.42 +3.26¥
(5.58)
0.012 +2.16
(7.17)
0.173 +4.46
(8.06)
0.017 +4.28
(5.61)
0.002
TFL -1.80
(3.02)
0.78 +5.77
(3.53)
p<0.0001 +7.60
(3.66)
p<0.0001 +8.20
(4.00)
p<0.0001 +7.48
(3.16)
p<0.0001
** SD = Standard Deviation. ₩Change indicates change in angle. ¥A negative sign before the mean shows the frontpack caused more of a decrease in angle than the backpack. A positive sign shows the
backpack caused more of a decrease in angle than the frontpack.

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Pairwise comparisons of TFL revealed significant differences between the backpack and
frontpack, at four of the five time points (Table 4), excluding unloaded standing.
In loaded standing the backpack caused a decrease in TFL when compared to the
frontpack, causing an increased FTP. For the duration of the treadmill walk the backpack
caused a mean decrease in TFL of at least 7.48° (p<0.001), when compared to the
frontpack. Mean changes and p-values are detailed in Table 4. Similarly to CVA, overall
the backpack caused more change in TFL than the frontpack with the backpack increasing
FTP more (Figure 9).
¥A negative sign (-) before the mean shows the frontpack caused more of a decrease in angle than the backpack.A positive sign (+)
shows the backpack caused more of a decrease in angle than the frontpack.
Figure 9: Change between backpack and frontpack (CVA and TFL) between
corresponding times when frontpack values are subtracted from the backpack values
-1.31
3.26
2.16
4.46 4.28
-1.79
5.77
7.6
8.2
7.48
-4
-2
0
2
4
6
8
10
Angle(degrees)
Change Between Times (Backpack - Frontpack = change)
Mean Change in Angle Between Backpack and Frontpack
CVA TFL

27
3.4 Secondary Outcomes
Data for the secondary outcomes of perceived discomfort (NRS) and exertion (BORG
RPE) was collected at four of the five time points, with loaded standing excluded. The
mean values for these outcomes are displayed in Appendix E (NRS) and Appendix F
(BORG RPE).
3.4.1 Question 1: Discomfort and Exertion Changes within Packs
In contrast to the primary outcomes, where differences in the data were analysed between
five time points, differences in data were analysed between two time points only for the
secondary outcomes. These were: the difference from unloaded standing – 0 minutes, and
from 0 minutes – 10 minutes. Mean differences between these time points within each
pack are presented in Table 5, with p-values showing all differences reached significance.
Both backpacks and frontpacks caused a significant continuous increase in
secondary outcome measure values from beginning to end of each testing session(Figure
10).

28
Table 5: Discomfort and Exertion Changes Within Backpack and Frontpack
Pair Backpack Frontpack
NRS Discomfort
Unloaded – 0
min
Mean Difference
(SD**) (degrees)
-1.00¥
-1.82
p value 0.017 0.000160
Significant Difference Between Packs:
p value 0.013
0 min – 10 min Mean Difference
(SD) (degrees)
-2.82 -3.00
p value 0.000055 0.000181
p value 0.772
BORG Exertion
Unloaded – 0
min
Mean Difference
(SD) (degrees)
-0.46 -0.91
p value 0.039 0.004
p value 0.091
0 min – 10 min Mean Difference
(SD) (degrees)
-2.41 -2.23
p value 0.000081 0.000272
p value 0.794
** SD = Standard deviation,¥A negative sign before the mean shows the frontpack caused more of a decrease in outcomes than the
backpack. A positive sign shows the backpack caused more of a decrease in outcomes than the frontpack

29
Figure 10: Secondary Outcomes: Mean Discomfort and Exertion scores
3.4.2 Question 2: Discomfort and Exertion Changes between Packs
Comparisons were made for secondary outcomes at 0 and 10 minutes.
Pairwise comparisons of perceived discomfort revealed significant differences
between backpack and frontpack, in favour of the backpack, at both time points.
Backpacks were 1.45±1.34 points lower on the NRS discomfort scale at 0 minutes when
compared to frontpacks at the same time (p<0.001). Backpacks also had lower NRS
scores than frontpacks at 10 minutes (1.64±2.24, p=0.005).
Pairwise comparisons of perceived exertion similarly revealed significant
differences in favour of the backpack. Backpacks were 0.96±1.7 points lower than the
frontpack on the BORG RPE scale at 0 minutes (p=0.016), and 0.77±1.27 points lower at
10 minutes (p=0.01). Although statistically significant, these differences are small.
Overall the backpack was significantly more comfortable to wear, and caused less
exertion throughout testing than the frontpack.
0
1
2
3
4
5
6
7
8
9
10
Unloaded 0 min 5 min 10 min
MeanScore
Time
Secondary Outcomes: Mean Scores
Backpack NRS Frontpack NRS Backpack BORG Frontpack BORG

30
4. Discussion
This study aimed to investigate the effects that a 10% bodyweight-loaded backpack and
frontpack, have on CVA and TFL in adult university students. The secondary aim was to
investigate the effects that these packs have on feelings of discomfort and exertion. The
results indicate that, while both packs induced postural changes, the backpack caused a
significantly greater increase in FHP and FTP. Both packs also caused significant
continuous increases in levels of perceived discomfort and exertion. However it was the
frontpack that consistently caused the greater change in this instance.
When considered individually, both packs caused a significant change from
baseline in CVA when immediately put on, where the backpack and frontpack increased
and decreased FHP respectively. Similarly TFL followed the same significant pattern.
These results are consistent with previous research where significant increases in FHP
and FTP from baseline were observed when a 10% bodyweight-loaded backpack was
applied (Kistner et al 2013; Brackley et al 2009). This indicates the high-responsiveness
of the subjects to external loads, even at the lower limit of 10% bodyweight. No
comparable research for these points was found for the frontpack.
Both packs caused significant increases in FHP and FTP from loaded standing at
0 minutes. Backpack postural angles were smaller compared to loaded standing during
the remainder of the 10 minute walkbut did not significantly get any smaller as the walk
went on. The same pattern applied to TFL in the frontpack condition. This is supported
by Kistner et al (2013) who found significantly increased FHP and FTP from loaded
standing to initial walking with a 10%-loaded backpack – however these values continued
to progressively decrease and increase respectively during a 6 minute walk. Comparable
research in this area is limited. Only one other study has compared both packs in terms of
dynamic postural change as the subject continuously mobilises – Fiolkowski et al (2006).
This study did not specify the duration of the treadmill walk or when outcome measures
were collected. Additionally they compared postural change between pack load, not in
relation to the walk, thus cannot be compared to the findings of this study.

31
Schoolbag weight has been advised not to exceed 10-20% bodyweight, although
research is often non-specific regarding the population this applies to. Kistner et al
observed that as backpack load increased from 10-20% bodyweight, CVA decreased and
TFL increased consistently (p<0.001) from pre- to post-walk. In the current healthy adult
population, 10% bodyweight was potentially sufficient to induce an immediate postural
change at these points, but not to induce further progressive change as the walkcontinued.
Postural change has been linked to load-carrying duration (Golriz and Walker 2012),
Kistner et al employed a 6 minute walk amongst a sample of primary-school children
(mean age=9.77 years). It is also possible that a 10 minute walk was not enough to
provoke further change in adults. No comparable research for frontpacks was identified.
Both packs caused a significant increase inFHP (p<0.05) between loadedstanding
and 10 minutes (Appendix D). Both also caused a significant increase in FTP (p<0.001)
between the same times. This suggests that although conditions weren’t sufficient to
induce progressive changes during the walk, CVA and TFL were still significantly
different between pre/post-walk. Brackley et al (2009) noted similar findings as FHP
(p=0.041) and FTP (p=0.003) increased after walking while wearing a 15% bodyweight-
loaded backpack. Fiolkowski et al did not compare differences in posture from pre/post-
walk to relate findings on the frontpack.
An unexpected finding of this study showed that frontpack FHP significantly
improved at 5 minutes, to a similar head position observed in unloaded standing
(p=0.012), and remained so for the remainder of the walk. This implies that walking with
the frontpack at 5 minutes was no different from unloaded standing. This finding is not
comparable to any other previous research to the author’s knowledge. In unloaded
standing, the back muscles naturally resist a flexion moment of the trunk (Motmans et al
2006). When an additional anterior weight is applied it is likely that the back muscles
must further resist the inclination towards TFL and possible that they are better equipped
than the anterior muscles to maintain normal posture during a relatively short period.
When considered together, backpacks produced greater FHP increases than
frontpacks at all four timepoints where the pack was worn. All changes except loaded

32
standing were significant. A similar pattern emerged concerning TFL angle – backpacks
produced greater FTP increases, where all four loaded timepoints were significant.
Fiolkowski et al (2006) found similar findings of significant increases in FHP and FTP
while wearing a 10-15% bodyweight-loaded backpack compared to a frontpack.
Additionally they found this FTP was strongly associatedwiththe FHP that was observed.
Motmans et al (2006) found abdominal muscle activity, which contributes to TFL, was
more than doubled when wearing a backpack versus a frontpack.
Reasons as to why the backpack caused a more negative postural change are
unclear and research comparing these two packs is limited. One potential explanation is
the influence of load placement on posture. A systematic review by Golriz and Walker
(2012) identified 12 studies investigating this. They concluded that low load placement
in backpacks was responsible for less postural deviations than other placements, however
load placement in frontpacks was not investigated. Each pack in the current study was
individually adjusted to be aligned with the superior aspect of the shoulder. Hand-weights
within the bag were located around L4-L5 in both conditions, thus this is presumed to
qualify as low load. It remains unestablished which pack produces more postural change
in response to low load placement making it possible the backpack could be responsible.
Future research in this area should investigate the postural effects of load placement in
frontpacks.
Continuous increases were observed in discomfort and exertion in both packs.
Minimal research in this area compares the change in these outcomes from pre- to post-
walk. Marsh et al (2006) showed exertion significantly increased after 5 minutes walking
with a 10% bodyweight-loaded backpack. Other studies compared differences in
discomfort between different backpack loads (Kistner et al 2013; Kistner et al 2012).
Some research has considered the possibilitythat somatic sensations such as discomfort
could contribute to perceived exertion (Goldstein 2010). Likewise, Borg (1982) stated
that perceivedexertion is “the single best indicator of the degree of physical strain”. This
study did not assess which sensation was experienced first. These outcomes possibly
influenced each other, contributing to the steady increase in both packs.

33
Interestingly, despite the backpack causing greater postural changes, the frontpack
caused significantly greater feelings of discomfort and exertion. This contradicts previous
research where no differences between packs were found in overall comfort or ease of
walking (Fiolkowski et al 2006). This inconsistency may be due to the length of the
treadmill walk, which was not reported by Fiolkowski et al. Possibly, they employed a
shorter walk which was not long enough to elicit any significant change. They also
applied a much slower walking pace of 0.75 strides per second which could contribute to
the non-significance, while mean walking speed of the present study was 5.12km/h.
Backpacks are reportedly worn by 90% of students (Reddy 2015). Frontpacks are
rarely used amongst students, making it possible that frontpacks provoked quicker muscle
fatigue, influencing the signifcant difference in discomfort and exertion levels between
packs. While wearing a backpack, rectus abdominus activity is 54-99% more, and erector
spinae activity is 30% less than in unloaded standing. In contrast, while wearing a
frontpack rectus abdominus activity is 10% less, and erector spinae is 100% more than
unloaded standing (Motmans et al 2006). This infers that the abdominal muscles are more
active than the back muscles when wearing a backpack and vice versa while wearing a
frontpack. Frontpacks demand more back muscle activity than what is accustomed with
a backpack, initiating quicker potential fatigue.
Oxford University Press (2016) defines a norm as “something that is usual,
typical, or standard”. It is reasonable to assume that wearing a schoolbag as a backpack
is a social norm and to wear a frontpack is considered to be outside this norm. Another
potential theory is that subjects were subconsciously aware that the frontpack was beyond
the bounderies of the accepted norm and consequently perceivedthe frontpack negatively.
This may also have contributed to the significant differences in discomfort and exertion
levels.

34
4.1 Limitations
This research should be considered within its limitation boundaries.
The small sample size may have increased the likelihood of experiencing Type 1
error – i.e. thinking there is a difference between the groups when there is not. Actions
were taken to minimise this possibilityby selecting an appropriate alpha level of (p<0.05)
(Pallant 2007). Despite the small size (n=22), this study is comparable with previous
research, employing a larger sample than some: Brackley et al (n=15), Motmans et al
(n=19), Fiolkowski et al (n=13), Wang et al (n=27). Results concerning the backpack
were also for the mostpart consistent with studies of larger samples: (Kistner et al 2013:
n=62).
The nature of testing ensured neither subjects nor assessor were blind to the pack
being tested. Although aware that posture was being analysed, subjects were, however,
blind to the angles of interest being measured to minimise the impact of the subject
actively correcting their posture. Additionally the pack order was randomised, eliminating
allocation bias. In trials with unadequate or unclear randomisation, treatment effects can
be overestimated by up to 40% compared to trials that employ proper randomisation
(Schul and Grimes 2002).
The short time-frame available for data collection, meant a convenience sample
within the clinical therapies department of the University of Limerick was taken. Of the
22 subjects who participated, 21 were physiotherapy students. This may affect the
transferability of the results to other student populations – due to the nature of their study,
physiotherapy students are unsurprisingly more aware of posture.
4.2 Implications for Practice
This postural analysis is transferable to a clinical setting as it uses inexpensive equipment
that is accessible to researchers and requires minimal training to administer.

35
This study’s results suggest that the conventional backpack induces significantly
greater FHP and FTP than a frontpack. Shifts in neck alignment can cause imbalanced
muscle performance and strain on cervical tissues and joints (Brackley et al 2009). Neck
pain patients, when compared to normal subjects, were found to have a smaller CVA
(Yip et al 2008). Within these patients, smaller CVA indicated greater neck disability.
Similarly, deviations from normal in trunk posture affect stress distribution within the
spine, causing strain and potential varying degrees of injury (Adams and Dolan 2005). If
the backpack caused significantly greater deviations, which in turn are known to
contribute to musculoskeletal complaints, it is reasonable to question its appropriateness
as the most common method of load carriage amongst students.
This study offered an alternative method of load carriage – a frontpack. This pack
was reported to cause considerably more discomfort and exertion. The same bag served
as both packs, and consequently did not include any special adaptations, e.g. additional
padding, that might be incorporated if a frontpack-specific design was used. Other
theories concerning why the frontpack was perceived as more uncomfortable have been
discussed. The differences incomfort and exertion reported in the current study, although
significant, are quite small, leaving their clinical importance open to interpretation.
Nonetheless, comfort is one of the most important attributes students considered when
choosing a backpack (Mackie et al 2003). Unless comfort is integrated, implications for
this pack are limited. Future research involving the effects of frontpacks should
incorporate frontpacks specifically designed for that purpose.
Despite their significance, due to the considerable scarcity of research in the area
and the limitations outlined, more robust studies are needed to verify these results before
any significant implications occur regarding the current load carriage practice of
university students.
5. Conclusion
This study compared the effects of a backpack and frontpack, loaded with 10%
bodyweight, on CVA and TFL after a 10 minute treadmill walk. Additionally it compared

36
their effects on secondary outcomes of perceived discomfort and exertion. Both packs
caused a significant and immediate change in CVA and TFL when immediately put on.
Overall, the backpack caused significantly greater, more negative changes in both CVA
and TFL when compared to the frontpack. However, the backpack caused significantly
less feelings of discomfort and exertion. Greater volumes of future studies incorporating
larger samples, more rigourous study designs and specialist frontpack models in adult
populations are warranted to confirm these findings.

37
6. References
Adams, M.A. and Dolan, P. (2005) ‘Spine biomechanics’, Journal of Biomechanics,
38(10), 1972-1983.
Bauer, D.H and Freivalds, A. (2009) ‘Backpack load limit recommendation for middle
school students based on physiological and psychophysical measurements’, Work,
32(3), 339–350
Borg, G.A.V. (1982) ‘Pschophysical bases of perceived exertion’, Medicine and Science
in Sports and Exercise, 14(5), 377-381
Brackley, H.M, Stevenson, J.M. and Selinger, J.C. (2009) ‘Effect of backpack load
placement on posture and spinal curvature in prepubescent children’, Work, 32,
351-360
Breivik, H., Borchgrevink, P.C., Allen, S.M., Rosseland, L.A., Romundstad, L., Breivik
Hals, E.K., Kvarstein, G. and Stubhaug, A. (2008) ‘Assessment of Pain’, British
Journal of Anaesthesia, 101(1), 17-24
Chansirinukor, W., Wilson, D., Grimmer, K. and Dansie, B. (2001) ‘Effects of backpacks
on students: measurement of cervical and shoulder posture’, Australian Journal
of Physiotherapy, 47(2), 110–116
Central Statistics Office (CSO) (2015) Statistical Yearbook of Ireland 2015: Education
[online], available: http://www.cso.ie/en/releasesandpublications/ep/p-
syi/statisticalyearbookofireland2015/society/education/, [accessed 09/02/2016]
Fiolkowski, P., Horodyski, M., Bishop, M., Williams, M. and Stylianou, L. (2006)
‘Changes in gait kinematics and posture withthe use of a front pack’, Ergonomics,
49, 885-894
Goldstein, E.B. (ed.) (2010) Encyclopaedia of Perception: Volume 1 & 2, USA: Sage

38
Golriz, S. and Walker, B (2012) ‘Backpacks. Several factors likely to influence design
and usage: A systematic literature review’, Work, 41, 1-13
Grimmer, K. and Williams, M. (2000) ‘Gender-age environmental associates of
adolescent low back pain’, Applied Ergonomics, 31(4), 343-360.
Grimmer, K., Dansie, B., Milanese, S., Pirunsan, U. and Trott, P. (2002) ‘Adolescent
standing postural response to backpack loads: a randomised controlled
experimental study’, BMC Musculoskeletal Disorders, 3(1), 10
Kendall, F.P., McCreary, E.K., Provance, P.G., Rodgers, M.M. and Romani, W.A. (2005)
Muscles: Testing and Function with Posture and Pain, 5th
ed., Philadelphia:
Lippincott Williams & Wilkins
Kistner, F., Fiebert, I. and Roach, K. (2012) ‘Effect of backpack load carriage on cervical
posture in primary schoolchildren’, Work, 41, 99-102
Kistner, F., Fiebert, I., Roach, K and Moore, J. (2013) ‘Postural Compensations and
Subjective Complaints Due to Backpack Loads and Wear Time in
Schoolchildren’, Pediatric Physical Therapy, 25, 15-24
Mackie, H.W., Legg, S.J., Beadle, J. and Hedderley, D. (2003) ‘Comparison of four
different backpacks intended for school use’, Applied Ergonomics, 34, 257-264
Marsh, A.B., DiPonio, L., Yamakawa, K., Khurana, S. and Haig, A.J. (2006) 'Changes in
posture and perceived exertion in adolescents wearing backpacks with and
without abdominal supports’, American Journal of Physical Medicine &
Rehabilitation, 85(6), 509-515
McEvoy, M.P. and Grimmer K. (2005) ‘Reliability of upright posture measurements in
primary school children’, BMC Musculoskeletal Disorders, 6:35

39
Motmans, R.R.E., Tomlow, S. and Vissers, D. (2006) 'Trunk muscle activity in different
modes of carrying schoolbags’, Ergonomics, 49(2), 127-138
Oxford University Press (2016) Oxford Dictionaries [online], available:
http://www.oxforddictionaries.com/us/definition/american_english/norm,
[accessed 09/02/2016]
Pallant, J.(2007) SPSS Survival Manual: A stepby stepguide to dataanalysis using SPSS
for Windows (Version 12), 3rd
ed., Maidenhead: Open University Press
Pascoe, D.D., Pascoe, D.E., Wang, Y.T., Shim, D.M. and Kim, C.K. (1997) ‘Influence of
carrying book bags on gait cycle and posture of youths’, Ergonomics, 40, 631–
641
Ramadan, M.Z. and Al-Shayea, A.M. (2013) ‘A modified backpack design for male
school children’, International Journal of Industrial Economics, 43, 462-471
Reddy, K. (2015) ‘A comparative study of a novel and school issued backpack on high
school adolescent posture at the New Forest High School in the eThekwini district
of KwaZulu- Natal’, unpublished thesis (M.A. Technology: Chiropractic),Durban
University of Technology, [online], available:
http://ir.dut.ac.za:8080/bitstream/handle/10321/1320/REDDY_2015.pdf?sequen
ce=1&isAllowed=y, [accessed 10/02/2016]
Schul, K.F. and Grimes, D.A. (2002) ‘Allocation concealment in randomized trials:
Defending against deciphering’. Lancet, 359, 614–8
Van Niekerk, S. M., Louw, Q., Vaughan, C., Grimmer-Somers, K. and Schreve, K. (2008)
‘Photographic measurement of upper-body sitting posture of high school students:
a reliability and validity study’, BMC Musculoskeletal Disorders, 9:113

40
Wang, C.X.G, Chow, D.H.K. and Pope, M.H. (2007) ‘Biomechanical effect of Load
carriage on spine curvature and repositioning ability in adolescents’, Proceedings
of the Fifth IASTED International Conference on Biomechanics, BioMech, 161-
166.
Yip, C.H., Chiu, T.T. and Poon, A.T. (2008) ‘The relationship between head posture and
severity and disability of patients with neck pain’, Manual Therapy, 13(2), 148-
154

41
7. Appendices
7. 1 Appendix A. – Postural Data Synthesis: Calculating CVA from Posture
Photographs
The angle of interest, CVA, is indicated by the area enclosed by the diagonal red line. We
will call this angle Δ.
SinΔ = o/h CosΔ = a/h TanΔ = o/a
In order to use trigonometry to calculate Δ, the lengths of the triangle (sides o, a and h)
must be calculated.
The x and y coordinates were also obtained for the point where the vertical reference line
(red), intersected the horizontal line from C7 – in order to calculate the length the side of
the triangle labelled o.
o = the distance between the y coordinates of tragus and intersection.
o = 756 – 895= -139 = 139 (distance can’t be a negative no.)
a = the distance between the x coordinates of C7 and Intersection.
a = 2184 – 2063 = 121
We can now calculate the CVA (Δ) by using tanΔ= o/a
CVA = Tan-1
o/a = Tan-1
(139)/(121) = 48.9603 = 48.96°
Tragus(2184,756)
C7(2063,895)
o
h
a Intersection (2184,895)

42
7. 2 Appendix B - Postural Data Synthesis: Calculating TFL from Posture
Photographs
The angle of interest, TFL, is indicated by the area enclosed by the diagonal redline. We
will call this angle Δ. SinΔ = o/h CosΔ = a/h TanΔ = o/a
In order to use trigonometry to calculate Δ, the lengths of the triangle (sides o, a and h)
must be calculated. The x and y coordinates were also obtained for the point where the
vertical reference line (red), intersected the horizontal line from C7 – in order to calculate
the length the side of the triangle labelled o.
o = the distance between the x coordinates of C7 and Intersection.
o = 2262 – 2063 = 199
a = the distance between the y coordinates of Intersection and ASIS.
a = 1534 – 895 = 639
We can now calculate the TFL (Δ) by using tanΔ= o/a
TFL = Tan-1
o/a = Tan-1
(199)/(639) = 17.2978 = 17.30°
ASIS(2262,1534)
C7(2063,895)
o
h a
Intersection(2262,895)

43
7.3 Appendix C – Written Informed Participant Consent (including consent to
have photographs published in study report if necessary)

44
7.4 Appendix D: Postural Change within Backpack and Frontpack condition between different time points
Pair Backpack Frontpack Pair Backpack Frontpack
CVA TFL
Unloaded
– Loaded
(Static)
Mean Difference (SD**)
(degrees)
*-1.87
(2.38)
*+2.70 (2.58) Unloaded
– Loaded
(Static)
Mean Difference (SD)
(degrees)
-3.38 (1.77) +2.56 (1.64)
P value 0.001 0.00007 P value P<0.000001 P<0.000001
% Change from Baseline 3.46 5.13 % Change from Baseline 20.63 15.80
95% Confidence Interval 0.81 – 2.92 -3.84 – -1.56 95% Confidence Interval 2.60 – 4.17 -3.29 – -1.84
P value 0.00005
P value P<0.000001
Loaded –
0 min
(Dynamic)
(degrees)
-4.84
(7.45)
-5.94 (5.31) Loaded – 0
min
(Dynamic)
(degrees)
-4.97 (3.08) -3.14 (3.35)
P value 0.000033 0.006 P value P<0.0001 P<0.0001
95% Confidence Interval 1.54 – 8.15 3.59 – 8.30 95% Confidence Interval 3.61 – 6.33 1.65 – 4.62
P value 0.440
P value 0.074

45
0 min – 5
min
(Dynamic)
(degrees)
0.76 (6.95) 3.06 (5.21) 0 min – 5
min
(degrees)
-0.50 (2.15) 0.10 (2.27)
P value 0.615 .012 P value 0.29 0.84
95% Confidence Interval -3.84 –
2.32
-5.37 – -0.75 95% Confidence Interval -0.45 – 1.45 -1.11 – 0.91
P value 0.211
P value 0.398
5 min – 10
min
(degrees)
0.39 0.20 (4.14) 5 min – 10
min
(degrees)
0.78 (1.79) 0.05 (1.70)
P value 0.723 0.823 P value 0.054 0.888
1.86
-2.04 – 1.64 95% Confidence Interval -1.57 – 0.02 -0.81 – 0.70
P value 0.881
P value 0.306
0 min – 10
min
(degrees)
+1.14
(6.31)
+3.26 (4.05) 0 min – 10
min
(degrees)
+0.28 (1.65) +0.15 (2.27)
P value 0.405 0.001 P value 0.438 0.756

46
(Dynamic)
1.66
-5.05 – -1.47 (Dynamic) 95% Confidence Interval -1.01 – 0.45 -1.161 – 0.86
P value 0.058
P value 0.849
Loaded –
10 min
(Dynamic)
(degrees)
-
3.70(5.12)
-2.68 (5.00) Loaded –
10 min
(Dynamic)
(degrees)
-4.70 (2.41) -2.99 (3.41)
P value 0.003 0.020 P value P<0.000001 0.00049
95% Confidence Interval 1.43 – 5.97 0.47 – 4.90 95% Confidence Interval 3.63 – 5.76 1.48 – 4.49
P value 0.353
P value 0.074
** SD = Standard deviation, * A negative sign (-) before the mean figures indicates a decrease in angle, while a positive sign (+) indicates an increase in angle. A decrease in angle indicates an increase in
forward-head posture (CVA) and TFL.

7.5 Appendix E - Mean NRS (Discomfort) Scores for Backpack and Frontpack
NRS Backpack Mean Standard Deviation 95% Confidence
Interval
Static Unloaded 0 0 0
Dynamic 0 min 1.00 1.604 .29 – 1.71
5 min 2.50 2.087 1.57 – 3.43
10 min 3.82 2.130 2.87 – 4.76
NRS Frontpack
Static Unloaded .64 1.399 .02 – 1.26
Dynamic 0 min 2.45 1.683 1.71 – 3.20
5 min 3.55 1.870 2.72 – 4.37
10 min 5.45 1.335 4.86 – 6.05

48
7.6 Appendix F - Distribution of BORG RPE Scores

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