fyp final draft pdf

Shauna Walsh

12123951

BSc. Physiotherapy

2016

2

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)

3

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 / /

4

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 Research Questions …………………………………………………....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 research in 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 walk with 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 load carriage 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 received from 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

13

gathering postural data were taken as the subject actively mobilised, not in a static

position. Therefore the ASIS, which remains relatively constant 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 reliability in

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 “worst discomfort imaginable”. The NRS is more

practical than the Visual Analogue Scale as it is easier to understand and visualise, and is

equally as sensitive (Breivik et al 2008). The Borg Rate of Perceived Exertion (Borg RPE)

scale was used to measure exertion. This scale ranges from 6 (“no exertion”) to 20

(“maximal exertion”), and is a widely used, 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 placed on 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 based on 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

15

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 direct line with the individual 3 meters away, mounted on a tripod at 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.

16

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

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

17

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

19

photographs, at all time points, for the first five participants. Reliability between 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 in terms of the key research questions 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?

21

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

22

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.

23

*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 applied in 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 in TFL from 0 to 10 minutes in either

pack (p=0.438,p=0.756).

53.99

52.13

47.2848.04 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

Ang

le (

deg

rees

)

Time

Change in CV Angle

CVA Backpack CVA Frontpack

24

* 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 revealed significant 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 7.528.3

16.2

18.76

15.62 15.73 15.78

0

2

4

6

8

10

12

14

16

18

20


Angl

e (d

egre

es)

Time

Change in TFL Angle

TFL Backpack TFL Frontpack

25

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.

26

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

7.68.2

7.48

-4

-2

0

2

4

6

8

10


Angl

e (d

egre

es)

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

Mea

n S

core

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 walk but 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 walk continued.

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 in FHP (p<0.05) between loaded standing

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 associated with the 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 possibility that somatic sensations such as discomfort

could contribute to perceived exertion (Goldstein 2010). Likewise, Borg (1982) stated

that perceived exertion 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 perceived the 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 possibility by 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 in comfort 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 with the use of a front pack’, Ergonomics,

49, 885-894

Goldstein, E.B. (ed.) (2010) Encyclopaedia of Perception: Volume 1 & 2, USA: Sage

http://www.cso.ie/en/releasesandpublications/ep/p-syi/statisticalyearbookofireland2015/society/education/

http://www.cso.ie/en/releasesandpublications/ep/p-syi/statisticalyearbookofireland2015/society/education/

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 step by step guide to data analysis 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

http://www.oxforddictionaries.com/us/definition/american_english/norm

http://ir.dut.ac.za:8080/bitstream/handle/10321/1320/REDDY_2015.pdf?sequence=1&isAllowed=y

http://ir.dut.ac.za:8080/bitstream/handle/10321/1320/REDDY_2015.pdf?sequence=1&isAllowed=y

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-1o/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-1o/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

fyp final draft pdf

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