Journal homepage: http://www.journalijar.com INTERNATIONAL JOURNAL
OF ADVANCED RESEARCH
RESEARCH ARTICLE
EFFECT OF BACKPACK ON GAIT KINETICS IN FRONTAL PLANE IN SCHOOL CHILDREN.
Lamiaa K.Elsayyad1, Hatem H. Allam2,3, Hala A.Abdelgawad4.
1. Lecturer at Faculty of Physical Therapy, Cairo University, Egypt.
2. Assisstant Professor, Department of Physical Therapy, College of Applied Medical Sciences, Taif University, KSA.
3. Lecturer at Faculty of Physical Therapy, Misr University for Sciences and Technology, Egypt .
4. Assistant Prof. at Faculty of Physical Therapy, Misr University for Sciences and Technology, Egypt.
Manuscript Info Abstract
Manuscript History:
Received: 14 December 2015
Final Accepted: 15 January 2016 Published Online: February 2016
Key words:
Backpack, Gait Analysis, Moment, Hip Abductor.
*Corresponding Author
Hatem H. Allam.
Frontal plane analysis during gait is an area which needs more investigations as the sagittal plane analysis is the always the subject of concern. Backpack carrying considered an everyday task during the school year. Carrying the backpack causes undesirable changes that affect different body systems. Purpose: The aim of our study was to determine the effect of backpack carrying on the hip abductors, the main pelvis stabilizer in the frontal plane, during gait. Thirty female normal children participated in this study. They were randomly selected from different schools at Giza government, Egypt. Their ages were ranged from 10-15 years old, their height ranged from 140-160 cm and their weight ranged from 40-50 Kg. Three dimensional motion analysis system with a force plate unit was used to measure the hip abductors moment during walking. The measurement was done with and without carrying a backpack weighted 15% of the subject’s weight. The results: The results revealed that there was a significant increase in the hip abductors moment during walking while carrying a backpack when compared with walking without carrying backpack. The significant increase was detected in both right and left sides.
Conclusion and recommendations: – Carrying a backpack weighted 15% of the body weight causes increase in the hip abductor moment and so increase the demands on the body during walking. Further studies are needed to determine the effect of lighter ones.
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Introduction:-
When the subject walk or stand with backpack the combined center of mass of subject and the backpack is deviated upward and backward. This deviation causes postural imbalance for static and dynamic conditions. Wearing a backpack leads to increase in the load supported by the musculoskeletal system, which may lead to various adaptation mechanisms by posture and forces acting on the human body. Many previous studies indicated that load carriage affected the kinematics and plantar pressures of walking. These biomechanical changes caused by load carriage might lead to the high levels of back pain, muscle discomfort, joint problems, metatarsal stress, fractures, metatarsalgia, and foot blisters observed in people wearing backpacks (Castro et al., 2015).
Backpack is one of the most convenient ways to carry books and school supplies. Improper use of backpacks or very heavy one increases the risk of spinal injury (Cottalorda et al. 2004). Also backpack carrying appears to place increased demands on gait (Chow et al., 2005).
A poorly positioned backpack seriously affects persons’ posture and gait. The alignment of the spine dramatically changes when the carried weight increases. Changes in gait parameters due to backpack loads are not entirely consistent and there is lack of data regarding load-bearing gait (Cottalorda et al., 2003 and Daniel et al., 2005).
Several recent studies have emphasize the effect of weight of school backpack on children, especially when its weight is over 20% of the child's body weight. Many children carry heavy backpacks which for some may weight 30% to 40% of their body weight. The maximum backpack weight should be 15% to 20% of the child’s body weight (Cottalorda et al., 2004). Carrying a heavy backpack can cause chronic, low-level trauma, and chronic shoulder, neck and back pain. (Leffert, 2000).
Adverse effects of backpack:-
1- Postural changes.
2- Struggling when putting on or taking off the backpack. 3- Pain associated backpack with wearing.
4- Numbness in arms and legs. 5- Red marks on the shoulders.
6- Increased muscular moments and power at the hip, knee and ankle indicated increasing the demand on the musculoskeletal system (Daniel et al., 2005).
Drerup et al., (2004) found an increase in the plantar peak pressures distribution in the regions of the large toe, metatarsals, and heel which directly proportion with the carried weight. The increase in planter pressure in large toe, metatarsals, and heel amounted to 0.54, 0.76, and 0.38 N/cm per kg additional load, respectively.
There is sequel of backpack on the vertical and anterior/posterior forces exerted on the upper and lower back. The lower back carry about 30% of the vertical force, and the remaining 70% is supported by upper back and shoulders. There is a direct relation between the peak forces on the upper and lower back and backpack mass. It can be concluded that the backpack exerts force on the lower back, which leads to the occurrence of low- back pain associated with weight carriage. The 70% which born by shoulder and upper back can be decreased to approximately 40% by transferring the load to the lower back through using an external frame backpack with a hip belt (Lafiandra et al., 2004).
Adolescents' response to increasing posterior load, regardless the backpack position was, anterior displacement of head, neck, shoulder, hip, thigh and knee in relation to the ankle joint. Shoulder deviasion affects the movement of all joints above it. This is response occurs due to the need for adjusting the body's center of gravity to accommodate a posterior load (Karen et al., 2002).
Hong and Cheung (2003) investigated the effect of carrying backpack loads of 0, 10, 15, and 20% of the body weight during gait. spatial and temporal parameters, trunk angles and trunk range of motion were analyzed. The results indicated that, both the backpack weight and walking distance influence trunk inclination. If trunk angle is taken as the criteria to detect the permitted backpack loads for children, the loads should not exceed 15% body weight. In addition, walking distance should be considered when allowed loads are determined.
Children, especially young ones, show a compensatory forward head posture when backpack loads are greater than 10%–15% of their body weight. On the other hand, further research is required to relate these findings to back pain. It is suggested that, loads less than 10%–15% of body weight are recommended to maintain normal postural alignment (Erica, 2002).
Backpack carrying can affect the spinal inter-segmental mobility. When a 22.5 kg backpack situated at the thoracic level (T9) of the trunk, a significant reduction of the inter-segmental mobility between S1-L3-T12 was observed. A decrease of inter-segmental mobility also appeared at the next level between L3-T12-T7. Also, a rise of the inter-segmental mobility between T7-C7-external occipital tuberosity was notable (Vacheron, 1999).
Another potential danger of heavy backpacks is the increased risk of falls in students who wear them. In a study conducted by Nancy and Talbott (2002), sway length and sway area were measured from the force plate records while executing a dynamic task. Different types, positions and the loads of backpack, were used. Results showed that during static and dynamic tests, sway length and sway area were significantly greater with increase the backpack weight. The type of backpack and the position of the backpack on the back had not significant effect. Other factors, including the history of pain associated with backpack wear and history of backpack related falls might be of greater importance to postural stability than the type or location of the backpack.
Students who carried packs weighting 25% of their body weight revealed balance problems while performing normal tasks such as climbing stairs or opening doors, which lead to increases their risk of falls. On the other hand, students who carried packs weighing 15% of their body weight controlled their balance to some extend. Those who carried 5% of their body weight maintained their balance more effectively compared with their peers who carried more weight. This instability may be related to biomechanical changes accompiend with the type of backpack worn or the placement of the backpack on the spine backpack (Nicole et al., 2001).
Postural stability and body position during wearing a backpack weights 20% of the body weight is significantly changed from situations in which no backpack or a backpack with 0 or 10% of the bodyweight is worn. Standing with a backpack that weighting 20% of body weight leads to an anterior movement of the shoulder and head, an increasing movement of the center of pressure and an anterior, superior deviation of the center of mass (Nancy and Talbott, 2004).
The position of the backpack also significantly affects postural stability and posture. When the backpack was worn in the high position, postural stability, as indicated by decreased movement of the center of gravity within the base of support, was greater than the low position but the head showed a more anterior posture. The type of backpack had no significant effect on postural stability or posture. In addition to the changes resulting from increase backpack weight and backpack position, it was found that, the gender, body mass index and age may also affect stability and posture when wearing backpacks ((Nancy and Talbott, 2004).
A study was conducted to investigate if standing dynamic balance was affected by using a backpack. The results revealed that movement velocity significantly decreased during backpack loaded trials. No significant difference was found in reaction time or maximum excursion with backpack loading (Palumbo et al, 2001).
It was noted that walking speed and cadence decreased significantly with increasing backpack load, while double support time increased (Wang et al., 2001). Kinematic changes were most obvious at the proximal joints, with a diminished pelvic motion but a significant increase in the hip sagittal plane motion. Increased muscular moments and power at the hip, knee and ankle indicated increasing demand with backpack load. Gait parameters showed different responses to different loads, which may be due to increase the demands, so it is recommended that the critical load to be approximately 10% body weight (Daniel et al., 2005). Changes in gait and posture resulting from load carriage are largely due to the body's attempt to increase its stability (Orloff and rabb, 2003).
La Fiandra et al., (2004), found a significant effect of backpack carriage on the ranges of transverse pelvic and thoracic rotation and the corresponding phase of pelvic and thoracic rotation. They said that the shorter stride length and higher cadence noticed when carrying a backpack is the result of decreased pelvic rotation. During unloaded walking, increases in pelvic rotation contribute to increases in stride length with increasing walking speed. The decreased pelvic rotation during load carriage requires an increased range of motion of hip to compensate for the decreased pelvic rotation. However, the increase in hip peak range is insufficient to fully compensate for the observed diminished pelvic rotation which in turn require an increase in stride frequency during load carriage to maintain a constant walking speed.
By Studying the effect of backpack loading on the gait pattern and compensatory mechanisms (which is important to the balance control) it was found that, there was an increased hip and knee joints flexion. Also, there was an increased trunk flexion. The speed decreased with loading on backs, but the stride length revealed less changes. In addition, we should consider that the responses to loads might be influenced by the strength of body (Wu et al., 2003).
A multi-joints coordination motor mode was activated to compensate the effect of loading; however, their roles are different; hips, knees and torso made the major role in the compensation while ankle joints made minor. The anterior angle of upper torso could be due to adjustment of the overall center of mass while loading on their backs. The greater the magnitude of loading on their backs, the greater the anterior angle of torso. After the heel strike, the flexion of hip and knee joints were effective for the shock absorption, which indicates that the stiffness of hip and knee joints can be used to absorb the shock and avoid the trauma of joints (Wu et al., 2003).
The Kinematic and kinetic data of the hip, knee and ankle joints were investigated during treadmill walking under three situations by Quesada et al., (2000). The three situations were 0%-body weight (BW) backpack load, 15%-BW load and 30%-BW load. The data was collected, immediately before and after each treadmill walking trial, for computing ankle, knee and hip joint range of motion and moments. It was revealed that during load carriage trials prior to treadmill marches the peaks of hip extension, knee extension and ankle plantar flexion moments significally increased with increasing backpack load. The post-march peaks in hip extension and ankle plantar flexion moments were similar to pre march with all loads, while notable pre-march to post-march decrease were noticed for knee extension moment peaks, at 15%-BW and 30%-BW load.
Pre-march joint loading data suggested that the knee may produce considerable compensations during backpack loaded marching, perhaps to diminish shock or reduce load somewhere else. Post-march kinetic data (particularly at 15%- BW and 30%-BW load), however, indicated that such knee compensations were not maintained and indicated that excessive knee extensor fatigue may happen prior to walking end, even though overall metabolic responses, at 15%BW and 30%-BW load, remained within recommended limits to avoid fatigue during prolonged work (Quesada et al. 2000).
Higher levels of upper and lower body moment were noticed during backpack use than during unloaded walking. The differences in moment between loaded and unloaded walking revealed that the main goal during loaded walking is to minimize upper body moment, which may reduce the likelihood of injury. Knowledge of the effects of load carriage on upper and lower body moment and related changes in coordination may provide insight into injury reduction mechanisms during load carriage (LaFiandra et al., 2004).
The purpose of the study:-
The purpose of the study was to determine the effect of backpack carrying on the hip abductor moment in the frontal plane. Hip abductors were selected as they considered the main stabilizer of the body during single limb stance and have an important role in maintaining the balance of the body during gait by decreasing the deviation of the body center of gravity.
Subjects and methods:-
1- Subjects:-
The subjects participating in this study was 30 female normal healthy students, were selected from different schools at Giza government.
Subjects Criteria:-
1. Age: ranged from 10-15 years old.
2. Height: ranged from 140-160 cm.
3. Weight: ranged from 40-50 Kg.
4. Free from any musculoskeletal abnormalities that affect walking.
5. They used to carry backpack as a method for carrying the school materials.
Methods:-
A- Instrumentations:- I-The backpack:-
Two straps backpack with the following criteria was used:-
1. Two wide shoulder straps with adjustable length.
2. Padded back to reduce pressure on the back, shoulders, and under arm regions.
3. Hip belt to transfer some of the backpack weight from the back and shoulders to the hips and torso.
4. The backpack was prepared by putting some of the school materials within it to weight 15% of the subject’s weight.
II- Three dimensional motion analysis system with a force plate unit:-
The system consists of:-
1. Motion capture unit
2. Wand kit:
3. Reflective markers:
4. Personal computer for data processing and analysis
B- Procedures:-
I- Subjects preparation:-
Before starting the procedures all subjects were instructed fully about the testing procedures and informed consents were obtained from parents (appendix I). The weight and height of the subject were measured and recorded. The bag was set to weigh 15% of the subject’s weight.
II- System calibration:-
Before the 3D capture was performed, camera system and the force platform were calibrated using a software calibration technique. This enables the cameras to pick up the markers position throughout the whole measurement volume.
III- Markers placement:-
Reflective markers were placed at anatomical landmarks as indicated by the manufacturer catalogue.
VI- Capturing:-
1. All subjects were instructed to walk freely with their normal walking speed on the walkway.
2. Capturing the kinetic data was performed to the subjects while walking without carrying any load and while carrying a backpack weighted 15% of the subject weight.
VI-Data analysis:-
The captured data were analyzed using software to calculate the hip peak abductor moment at each trial.
Study and Statistical design:-
The research design of this study was case control design and the statistical analysis was done using MANOVA.
Results:-
The independent variable in this study was the backpack carrying and the dependent variable was the hip abductor moment. The dependent variable had a two levels (right and left sides) so MANOVA test was used.
The results of the study showed that the mean value of the right hip abductor moment (MRt.) and that of the left hip abductor moment (MLt.) without carrying the backpack were0.4033/Kg (±0.0486) and 0.4013N.m/Kg (±0.0511) respectively. During carrying the backpack the values became0.477N.m/Kg (±0.054).and 0.473N.m/Kg (±0.0573) for right and lift sides respectively. There was a significant increase in the values of hip abductors moments during walking while carrying the backpack.
Table (1):MANOVA and LSD tests for hip abductor moment with and without carrying backpack.
X ± SD Without carrying With carrying
MRt MLt. MRt MLt.
0.4033±0.0486 0.4013±0.0511 0.477±0.054 0.473±0.0573
MANOVA
F 76.66
P <0.05
LSD
With carrying vs Without carrying p
MRt vs MRt <0.05
MLt vs MLt. <0.05
Discussion:-
The results of the current study showed a significant increase in the hip abductor moment during gait as a result of backpack carrying. This may be attributed to the increased demands on the muscular activity due to the weight of the backpack.
The hip abductors muscles play an important role in support of the body weight especially during single limb stance. The body weight acting through the center of gravity tends to drop the pelvis in the frontal plane at the hip joint by creating adduction moment. This action of the body weight is counterbalanced by the action of the hip abductors which create abduction moment (Jacobs et al., 2007).
So the increase in the body weight will increase the demands on the hip abductors which should increase their moment to withstand the increase in the body weight. In the current study carrying the backpack was the source of body weight increase which required the increased activity of hip abductor.
Our results come in agreement with Chow et al., (2005) who conducted a study on gait of 22 normal adolescent girls. Gait variables were measured using backpack loads of 0, 7.5, 10.0, 12.5 and 15.0% body weight. Temporal and distance variables, ground reaction force and joint kinematic, moment and power parameters were analyzed. They concluded that, walking speed and cadence decreased significantly with increasing backpack load, while double support time increased. Kinematic changes were most marked at the proximal joints, with a decreased pelvic rotation but a significant increase in the hip sagittal plane motion. Increased moments and power at the hip, knee and ankle indicated increasing demand with backpack load.
The results of Hong &Brueggemann, (2000), supported our findings. They investigate the gait pattern, heart rate and blood pressure in children carrying school bags of 0 (as control), 10, 15 and 20% of their body weight during walking on a treadmill. When compared to the 0% load trial, the 20% load trial showed a significant increase in trunk forward flexion, double support and stance time. Also, a decreased trunk angular motion, swing time were observed. A prolonged blood pressure recovery time was recorded. The 15% load trial showed a significant increase in trunk forward flexion and prolonged blood pressure recovery time. No significant difference was found in the measured variables between the 10 and 0% load trials
Also, Mackenzie et al., (2003), findings were parallel to our findings. They stated that, back pain and deformity are commonly noticed in adolescents. There has been extensive discussion in the unscientific literature regarding the relation between potential for back pain and spinal deformity with backpack use. The scientific literature on this subject is scant but is increasing. Epidemiologic studies have recognized risk factors associated with back pain in adolescents and daily use of a heavy backpack. A school bag weighing more than 15% to 20% of a child's weight is accompanying with back pain, and inappropriate use of the backpack can cause changes of posture and gait. There is no evidence that structural spinal deformity can be a result from backpack use. Children who have back pain are at increased risk of having back pain as adults
Conclusion:-
According to the results of this study, it can be concluded that carrying a backpack with a weight of 15% of the subject’s body weight will significantly increase the hip abductors moment. This increase in the hip abductors moment indicates increased demands on the subjects carrying the backpack, which can adversely, affects the subjects’ health.
Recommendations:-
1. The weight of the backpack should be less than 15% of the subject weight.
2. Repeat the same study using different weights (lessthan15% of the body weight) to determine the safest one.
3. Conducting further studies to assess the other gait parameters.
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