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The effect of school bag design and load on spinal

posture during stair use by children
a b c
Youlian Hong , Daniel Tik-Pui Fong & Jing Xian Li
a
Department of Sports Medicine , Chengdu Sports University , Chengdu, China
b
Department of Orthopaedics and Traumatology, Prince of Wales Hospital, Faculty of
Medicine , The Chinese University of Hong Kong , Hong Kong, China
c
School of Human Kinetics, Faculty of Health Sciences , University of Ottawa , Ottawa,
Canada
Published online: 22 Nov 2011.

To cite this article: Youlian Hong , Daniel Tik-Pui Fong & Jing Xian Li (2011) The effect of school bag design and load on
spinal posture during stair use by children, Ergonomics, 54:12, 1207-1213, DOI: 10.1080/00140139.2011.615415

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 Ergonomics
Vol. 54, No. 12, December 2011, 1207–1213

The effect of school bag design and load on spinal posture during stair use by children
Youlian Honga, Daniel Tik-Pui Fongb* and Jing Xian Lic
a
Department of Sports Medicine, Chengdu Sports University, Chengdu, China; bDepartment of Orthopaedics and Traumatology,
Prince of Wales Hospital, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China; cSchool of Human
Kinetics, Faculty of Health Sciences, University of Ottawa, Ottawa, Canada
(Received 21 January 2011; final version received 12 August 2011)

Thirteen male children ascending and descending stairs with loads that equalled 0%, 10%, 15% and 20% of their
body weight were the subject of our research: the boys were wearing an asymmetrical single-strap athletic bag or a
symmetrical double-strap backpack during our experiments with them. The maximum spinal tilt to the loading side
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and to the support side, and the range of spinal motions, were obtained by using a motion analysis system. Our
results showed that symmetry of spinal posture was observed both when they ascended staircase with all loads and
descended in a backpack. When carrying an athletic bag with 15% and 20% of their body weight while ascending the
staircase, the lateral spinal tilt to the supporting side was significantly increased. We concluded that a symmetrical
backpack with a load not exceeding 20% or an asymmetrical single-strap athletic bag with a load not exceeding 10%
should be recommended for school children in order to promote safer staircase use.

Statement of Relevance: Children carrying heavy school bags may develop spinal problems. This study suggested
that when they are using stairs, a symmetrical backpack with a load within 20% body weight is acceptable for
them. When they are carrying an asymmetrical single-strap athletic bag, the bag’s weight should not exceed 10% of
the body weight in order to avoid excessive spinal tilt.
Keywords: biomechanics; load-bearing; carrying; child; orthopaedics; gait

1. Introduction backpack significantly increased forward trunk lean

The wearing of heavy backpacks has prompted extensive (Hong and Cheung 2003), prolonged blood pressure
discussion among children, parents and healthcare recovery time (Hong and Brueggemann 2000), increased
professionals about its potential to cause shoulder oxygen uptake and energy expenditure (Hong et al.
pain, neck pain and back pain and even spinal deformity 2000), increased breathing frequency (Li et al. 2003) and
(Mackenzie et al. 2003, Trevelyan and Legg 2010). A increased trapezius muscle activity and fatigue (Hong
recent study suggested that the weight of a school bag et al. 2008). When the child was standing, the heavy load
correlated with the magnitude of body sway, and that also altered the posture of a healthy subject
the increased body sway may be related to balance (Chansirinukor et al. 2001), and it even introduced an
impairment and perhaps to a higher risk of falls (Pau and imbalance in the medial-lateral direction in girls affected
Pau 2010). The weight of school bags in terms of the by adolescent idiopathic scoliosis (Chow et al. 2006).
percentage of the body weight of children has been Besides the load itself, the carrying method also affected
reported as 17.7% in the US (Pascoe et al. 1997), 20% in the body posture. Kinoshita (1985) found that an
Italy (Negrini and Carabalona 2002) and 20% in Hong asymmetrical carrying method caused more spinal tilt in
Kong (Hong Kong Society for Child Health and level walking, whereas Troussier et al. (1994) found that
Development 1998). These heavy loads have caused there was a risk that it could cause low back pain. Pascoe
spinal symptoms (Johnson et al. 1995), back pain (Sheir- et al. (1997) also found that an asymmetrical school bag
Neiss et al. 2003), fatigue (Negrini and Carabalona carrying method, whether the child was carrying either a
2002), breathing restriction (Lai and Jones 2001) and single-strap backpack or a shoulder-supported athletic
even acute injuries (Wiersema et al. 2003). bag, significantly increased lateral spinal deviation
Numerous studies have been conducted to demon- during level walking.
strate the biomechanical effects of load carriage. In level In Hong Kong, schools and living places are often
overground walking and walking on a treadmill, a load multi-storyed buildings, and thus stair use is a common
of 15% body weight or more with a double-strap daily functional activity. Previous studies have shown

*Corresponding author. Email: dfong@ort.cuhk.edu.hk

ISSN 0014-0139 print/ISSN 1366-5847 online

Ó 2011 Taylor & Francis
http://dx.doi.org/10.1080/00140139.2011.615415
http://www.tandfonline.com
 1208 Y. Hong et al.

that stair climbing and level walking necessitate two total of eight trials from a combination of four
different kinds of gait (Loy and Voloshin 1991, different loads in two different school bag types were
McFadyen and Winter 1998). Because one has to performed by each participant in a random sequence.
propel the body forward and also upward or The four load conditions equalled 0%, 10%, 15% and
downward in stair use, doing so with a heavy school 20% of the participant’s body weight. Percentage
bag may result in increased dynamic loading on the weight instead of absolute weight was used in order to
body. Hong et al. (2003) found that a load of 10% achieve normalisation across the range of participants.
body weight or more produced a significant forward The required weight was prepared by filling the school
spinal lean when ascending a staircase. Moreover, bag with objects that students usually bring to school,
greater spinal motion in the sagittal plane was such as books, pencil box, drawing material, PE t-shirt
observed when the subjects carried a single-strap and shoes. The two types of school bag were: (1) a
shoulder-supported athletic bag, which represented single-strap athletic bag; and (2) a double-strap
an asymmetrical carrying method. In kinetics, Hong backpack. In the trials with the single-strap athletic
and Li (2005) found that increased peak plantar force bag, the bag was placed on the left with the strap
was used during the descent of a staircase with a load across the right shoulder – this represented an
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in an athletic bag which represented 10% body weight. asymmetrical carrying method (Figure 1a), with the
However, there have been few studies reporting the left as the loading side and the right as the supporting
spinal biomechanics in the frontal plane during stair side. In the trials with the double-strap backpack, the
use. fillings in the bag were arranged in a symmetrical way,
It is generally understood that stair use, especially with a strap across each shoulder – this represented a
when ascending a staircase, is more physically symmetrical carrying method (Figure 1b).
demanding compared to level walking. The demands A video camera (JVC DVL9800, Japan) was
of load carriage and carrying method may impose a positioned at the bottom of the staircase, viewing
greater challenge to the spine, and may thus lead to a upwards, to record the spinal movements in a frontal
higher risk of spinal symptoms. While the effect on plane with a 50 Hz filming rate and a 1/250s shutter
sagittal plane spinal motion and plantar force has been speed. The camera zoom level was adjusted to produce
demonstrated, the effect on the frontal plane spinal a full-picture view when the participant stepped on the
motion has not been investigated. This study reported middle of the staircase for one complete gait cycle
on the effects of load carriage and school bag type on (from the 15th to the 17th step). Before the experiment,
spinal posture during stair use by children. each subject was instructed to stand on the 16th step in
his anatomical position without carrying any load, and
such posture was videotaped to define the initial
2. Methods vertical neutral position. The films were captured and
Thirteen male children (mean + SD: age: 12.2 + 1.0 saved in a computer. Video data of one complete gait
years; mass: 47.1 + 9.7 kg; height: 159.7 + 9.7 cm) cycle as identified by the moment of foot strike, as
participated in this study. The test was carried out at a indicated by the markers at the toe, was trimmed
33-step staircase situated in between the audience during every ascending and descending trial. The video
seating at the university sports field. All participants data were digitised by a motion analysis system (Ariel
were free of injury on the testing day, and had no Performance Analysis System, USA). For the purposes
history of injury that caused them to have an abnormal of this experiment, the spine was defined as being the
gait or difficulties when using stairs. Completed line joining the mid-point between the shoulders and
consent forms from the participants and their parents the mid-point between the hips, and the spinal posture
were collected before the test. Participants were each was defined as the angle between the spine and the
required to dress in a black tight t-shirt and black initial vertical position of each participant. The
shorts, with six reflective skin markers attached at the maximum spinal tilting angle to the left and to the
left and right shoulder, hip and toe. The black dressing right and the range of the spinal tilting angle were
and the reflective markers were to facilitate the averaged over the participants at each load and with
automatic video image digitisation when we analysed each school bag type when they ascended and
the video data in the motion analysis software. descended the staircase.
In each of the trials, each participant ascended and Both for the ascent and the descent of the staircase,
descended the staircase carrying different loads in a two-way multivariate analysis of variance (bag
school bags of a different type. He started at the type 6 load) with repeated measures (MANOVA)
bottom of the 33-step staircase, walked up to the top was applied on the dependent variables in order to
and then walked down to the bottom at his natural identify any significant effects caused by bag type and
cadence; they were required to do this three times. A load. The analysis was conducted with a statistical
 Ergonomics 1209
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Figure 1. The two carrying methods investigated in this study: (a) the asymmetrical carrying method with a single-strap
athletic bag, with the school bag placed on the left (loading side) and the school bag strap on the right shoulder (supporting
side); (b) the symmetrical carrying method with a double-strap backpack.

analysis software (Statistical Package for the Social tilting angle to the right, and the range of the spinal
Sciences, US). If an interactive effect was found, a tilting angle at each load with each school bag type in
stratified analysis of variance (ANOVA) was ascending and descending the staircase, respectively.
conducted to demonstrate the load effect on each bag The MANOVA showed a significant interactive (bag
type (for all parameters), and the bag type effect on type 6 load) effect (Wilk’s lambda ¼ 0.664,
each load (for a range of spinal motion only), with F ¼ 2.646, p ¼ 0.023). Therefore, a stratified ANOVA
Tukey pairwise comparisons conducted between the was conducted.
0% load and the other loads. If not, an ANOVA on With regard to ascending the staircase, an ANOVA
each main effect was conducted. In order to further showed that a significant difference was found in the
demonstrate the symmetry of spinal posture, maximum tilting angle to the left and also to the right
independent t-tests were conducted between the for a single-strap athletic bag (p 5 0.05). Tukey
maximum tilting angle to the left and to the right for pairwise comparisons showed that the maximum
each bag type and load. Independent t-tests were also tilting angle to the left (the loading side) was
conducted for the ascent and the descent of the significantly reduced from 3.98 to 1.58 when the load
staircase in every pair of parameters. The statistical was increased from 0% to 20% body weight
significance was set at a 95% level of confidence. (p 5 0.05). The maximum tilting angle to the right
(the supporting side) was significantly increased from
6.08 to 8.38 when the load was increased from 0% to
3. Results 15% body weight (p 5 0.05) and it increased to 8.68
Table 1 shows the mean and standard deviation of the when the load was increased from 0% to 20% body
spinal posture parameters, including the maximum weight (p 5 0.05). No significant difference was found
spinal tilting angle to the left, the maximum spinal for the maximum spinal tilting angles for the
 Downloaded by [Rensselaer Polytechnic Institute] at 23:18 08 April 2015

1210

Table 1. Maximum and range of spine tilting angles for stairs ascending and descending with loads in single- and double-strap school bag.

Single-strap athletic bag Double-strap backpack Range of spinal motion (8)

Load (% body Max. angle – Max. angle – p value Max. angle – Max. angle – p value Single-strap Double-strap p value
weight) left (8) right (8) of t-test left (8) right (8) of t-test athletic bag backpack of t-test
0%
Stairs ascending 3.9 (2.1) 6.0 (3.5) 0.084 5.5 (2.1) 5.9 (2.2) 0.656 9.9 (2.7) 11.4 (2.7) 0.183
Stairs descending 1.5 (1.8) 3.6 (1.9) 0.008* 1.9 (1.6) 2.6 (1.7) 0.277 5.1 (1.5) 4.5 (1.3) 0.237
p value of t-test 0.005* 0.044* 50.001* 50.001* 50.001* 50.001*
10%
Stairs ascending 4.0 (2.1) 6.1 (3.8) 0.090 5.4 (2.1) 6.5 (3.1) 0.290 10.1 (3.8) 11.9 (2.7) 0.167
Stairs descending 1.1 (1.9) 3.6 (2.1) 50.001* 2.7 (0.9) 2.1 (1.6) 0.290 4.7 (2.1) 4.8 (1.3) 0.957
p value of t-test 0.001* 0.050* 50.001* 50.001* 0.001* 50.001*
15%
Stairs ascending 2.7 (3.4) 8.3 (4.4) 0.001* 5.4 (2.0) 5.3 (1.8) 0.858 11.0 (4.1) 10.7 (2.5) 0.850
Y. Hong et al.

Stairs descending 2.1 (2.4) 4.2 (2.4) 0.036* 2.5 (1.3) 2.2 (1.4) 0.511 6.3 (1.9) 4.7 (1.4) 0.020*
p value of t-test 0.613 0.008* 50.001* 50.001* 0.001* 50.001*
20%
Stairs ascending 1.5 (3.2) 8.6 (3.1) 50.001* 5.4 (1.6) 5.7 (2.5) 0.769 10.1 (2.0) 11.1 (1.9) 0.240
Stairs descending 2.5 (2.6) 4.7 (2.7) 0.046* 2.6 (1.0) 2.8 (2.1) 0.710 7.2 (2.6) 5.4 (1.3) 0.032*
p value of t-test 0.396 0.002* 50.001* 0.004* 0.004* 50.001*

Notes: *¼ significant difference, p 5 0.05. Statistical analysis program shows only to p 5 0.001.
 Ergonomics 1211

double-strap backpack and also for the range of spinal (age ¼ 11–13 years), who each carried different school
motion for both designs of school bag. For the single- bags with a load of 17.6% body weight. They reported
strap school bag, independent t-tests showed that there that the lateral spinal tilt was much greater when an
was a significant difference between the tilting angles to asymmetrical carrying method was used than it was
the left (the loading side) and to the right (the with a symmetrical carrying method. When walking
supporting side) when the load reached 15% and without a load, the lateral spinal tilt was 1.98. When
20% body weight (p 5 0.05). carrying a load in a two-strap backpack, the lateral
In descending the staircase, the tilting angles and spinal tilt was about 2.18 and there was no significant
the range of spinal motions were generally smaller than difference. However, when the load was placed in a
those during ascending the staircase. An ANOVA one-strap backpack or in a one-strap athletic bag, the
showed no significant difference between different lateral spinal tilt was significantly increased to 8.58 and
loads and types of school bag. 8.38, respectively. With regard to stair use, Hong et al.
Tukey pairwise comparisons showed that there (2003) found that load carriage in an asymmetrical
were significant differences between each pair of school bag caused a greater amount of spinal sagittal
parameters among ascending and descending the motion. In kinetics, a significant increase of peak
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staircase, except that the spinal tilting angle was to plantar force was found when the load was 10% body
the left with a 15% and 20% load in a single-strap weight in an asymmetrical load-carrying method when
athletic bag. ascending a staircase; however, such a significant
increase was found when the load reached 15% body
weight when a symmetrical load-carrying method was
4. Discussion used (Hong and Li 2005).
The range of spinal motion did not differ among loads In this study, significant spinal tilt was observed
in relation either to the single-strap athletic bag or the both in the ascent and the descent of the staircase with
double-strap backpack both when ascending and a load in a single-strap athletic bag. Moreover, the
descending the staircase. However, in each load 6 range of spinal motion was 9.9–11.98 when ascending
carrying method combination, it was found to be the staircase, which was greater than that in level
greater when ascending the staircase. The range was walking (8.58), as was reported by Pascoe et al. (1997).
about 4.5–7.28 when descending the staircase and 9.9– These results, together with the findings in previous
11.98 when ascending the staircase. The range of studies, suggest that an asymmetrical carrying method
motion did not differ between the two types of school imposes greater stress on the spine, especially when
bag with regard to all of the loads. For the double- ascending a staircase with a load of 15% body weight
strap backpack, which represented a symmetrical or more. The nature of the locomotion in stair use is
carrying method, the spinal tilting angles to the left different from that used in level walking. In level
and to the right did not differ either between each other walking, a person stays at the same horizontal level; he
or among the loads both as to the ascent and the therefore propels his body (and thus his centre of
descent of the staircase. However, it was significantly gravity) in only a forward direction. In stair use, a
increased from 1.9–2.88 in the descent of the staircase person needs to propel his body forwards and also
to 5.3–6.58 in the ascent of the staircase. These findings either upwards or downwards. In doing this, he has to
suggest that the spinal motion was generally much bend his legs to raise or lower one side of the body to
larger during ascending than it was during descending. land on the next step. This produces greater spinal
The load effect was not significant. Moreover, the motion when compared to level walking. The tilt was
similar spinal tilting angles to the left and to the right more significant when there was a heavy load (415%
with a double-strap backpack suggested that this body weight) in an asymmetrical carrying method.
carrying method is symmetrical in the human frontal The spinal tilt was to the supported side (the side
plane. with the school bag strap on the shoulder) instead of to
Before this investigation, the authors did not expect the loading side. This is the human adaptation for
if a spinal tilt would be to the loading side or the minimising the disturbance to the balance and stability
support side when a single-strap athletic bag is being of the body’s centre of mass. When a single-strap
carried. The results of this study showed that the spinal athletic bag is loaded on the left, the centre of gravity
tilt was to the support side (right) when the load of the person plus the school bag shifts to the left. This
reached 15% and 20% of the body weight. Generally, introduces posture instability, the person has,
the tilting angles during the ascent of the staircase were therefore, to tilt the body to the right in order to shift
higher than the descent. the centre of gravity back to the middle of the
With regard to level walking, Pascoe et al. (1997) supporting base, which is between both feet. Doing this
studied the effect on lateral spinal tilt in 10 subjects over a prolonged period requires repetitive activation
 1212 Y. Hong et al.

of the spine’s stabilising muscles. This may lead to Chow, D.H., et al., 2006. The effect of backpack weight on
muscle pain, low back pain and chronic injuries. the standing posture and balance of schoolgirls with
adolescent idiopathic scoliosis and normal controls. Gait
Therefore, we suggest that further study on spine- and Posture, 24 (2), 173–181.
stabilising muscle activity and fatigue is required. Chow, D.H.K., Leung, K.T.Y., and Holmes, A.D., 2007.
Although a double-strap backpack is symmetrical Changes in spinal curvature and proprioception of
in the frontal plane, it is still asymmetrical in the schoolboys carrying different weights of backpack.
sagittal plane; this is because all the loads are at the Ergonomics, 50 (12), 2148–2156.
Chow, D.H.K., et al., 2010. Short-term effects of backpack
posterior aspect of the human spine. There was also load placement on spine deformation and repositioning
another recent study which proposed a modified error in schoolchildren. Ergonomics, 53 (1), 56–64.
double backpack design in which part of the load Hong, Y. and Brueggemann, G., 2000. Changes of gait
would be placed at the chest area (Kim et al. 2008). pattern in 10 years old children during treadmill walking
Such a design should successfully reduce the stress on with increasing loads. Gait and Posture, 11 (3), 245–
259.
the spine. Chow et al. (2007) suggested that a backpack Hong, Y. and Cheung, C.K., 2003. Gait and posture
load would cause the flattening of the lumbar lordosis responses to backpack load during level walking in
and the upper thoracic kyphosis, and thus produce children. Gait and Posture, 17 (1), 28–33.
Hong, Y., Lau, T.C., and Li, J.X., 2003. Effects of loads and
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immediate changes to the spinal curvature. They also

suggested that a consistent shifting of the load position carrying methods of school bags on movement
kinematics of children during stair walking. Research in
could help to solve the problem of the stressing of the Sports Medicine, 11 (1), 33–49.
spine (Chow et al. 2010). We therefore believe that a Hong, Y. and Li, J.X., 2005. Influence of load and carrying
different method of carrying a single-strap athletic bag methods on gait phase and ground reactions in children’s
should be less harmful. We therefore suggest that stair walking. Gait and Posture, 22 (1), 63–68.
further research thereon would be very worthwhile. Hong, Y., Li, J.X., and Fong, D.T.P., 2008. Effect of
prolonged walking with backpack loads on
We commented that a future study should include trunk muscle activity and fatigue in children. Journal
the effect of prolonged walking on the spinal posture. of Electromyography and Kinesiology, 18 (6), 990–
In the current study, in which the effect of fatigue was 996.
not encountered, the subjects were able to well carry a Hong, Y., et al., 2000. Effects of loads carriage on heart rate,
loaded single-strap athlete bag on their supporting blood pressure and energy expenditure in children.
Ergonomics, 43 (6), 717–727.
shoulder. We believe that in case of fatigue, the Hong Kong Society for Child Health and Development,
subjects may fail to carry the bag with this manner, 1998. The weight of school bags and its relation to spinal
and may tilt the spine back to the loading side. deformity. Hong Kong: The Department of Orthopaedic
Therefore, like other studies on the prolonged effect of Surgery, University of Hong Kong, The Duchess of Kent
load carriage in level walking, future studies should Children’s Hospital.
Johnson, R.F., Knapik, J.J., and Merullo, D.J., 1995.
encounter this effect in load carriage in stairs climbing. Symptoms during load carrying: effects of mass and load
distribution during a 20-km road march. Perceptual and
Motor Skills, 81 (1), 331–338.
5. Conclusion Kim, M.H., et al., 2008. Changes in neck muscle
This study suggested that the spinal posture was not electromyography and forward head posture of children
when carrying schoolbags. Ergonomics, 51 (6), 890–
altered when climbing stairs with a double-strap 901.
backpack. However, a significant spinal tilt to the Kinoshita, H., 1985. Effects of different loads and carrying
support side was observed when a single-strap athletic systems on selected biomechanical parameters describing
bag was being carried. The spinal tilt was much more walking gait. Ergonomics, 28 (9), 1347–1362.
significant when the load was 15% body weight or Lai, J.P. and Jones, A.Y., 2001. The effect of shoulder-girdle
loading by a school bag on lung volumes in Chinese
more. We therefore conclude that a symmetrical primary school children. Early Human Development, 62
backpack or an asymmetrical single-strap athletic bag (1), 79–86.
with a load not exceeding 10% should be recom- Li, J.X., Hong, Y., and Robinson, P.D., 2003. The effect of
mended for school children in order to avoid spinal load carriage on movement kinematics and respiratory
posture alteration during stair use. Furthermore, we parameters in children during walking. European Journal
of Applied Physiology, 90 (1–2), 35–43.
also suggest that further study of muscle activity be Loy, D.J. and Voloshin, A.S., 1991. Biomechanics of stair
carried out. walking and jumping. Journal of Sports Science, 9 (2),
137–149.
Mackenzie, W.G., et al., 2003. Backpacks in children.
References Clinical Orthopaedics and Related Research, 409, 78–84.
McFadyen, B.J. and Winter, D.A., 1998. An integrated
Chansirinukor, W., et al., 2001. Effects of backpacks on biomechanical analysis of normal stair ascent and
students: measurement of cervical and shoulder posture. descent. Journal of Biomechanics, 21 (9), 733–
Australian Journal of Physiotherapy, 47 (2), 110–116. 744.
 Ergonomics 1213

Negrini, S. and Carabalona, R., 2002. Backpacks on! Trevelyan, F.C. and Legg, S.J., 2010. The prevalence and
Schoolchildren’s perceptions of load, associations with characteristics of back pain among school children in
back pain and factors determining the load. Spine, 27 (2), New Zealand. Ergonomics, 53 (12), 1455–1460.
187–195. Troussier, B., et al., 1994. Back pain in school children. A
Pascoe, D.D., et al., 1997. Influence of carrying book bags on study among 1178 pupils. Scandinavian Journal of
gait cycle and posture of youths. Ergonomics, 40 (6), 631– Rehabilitation Medicine, 26 (3), 143–146.
641. Wiersema, B.M., Wall, E.J., and Foad, S.L., 2003. Acute
Pau, M. and Pau, M., 2010. Postural sway modifications backpack injuries in children. Pediatrics, 111 (1), 163–
induced by backpack carriage in primary school children: 166.
a case study in Italy. Ergonomics, 53 (7), 872–881.
Sheir-Neiss, G.I., et al., 2003. The association of backpack
use and back pain in adolescents. Spine, 28 (9), 922–930.
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