• Journal of Korean Physical Therapy Science
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• v.18 no.4
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• pp.81-85
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• 2011

Purpose : The purpose of this study was to investigate the changing plantar foot pressure by the backpack load of 0, 10, 15, and 20% of their body weight while level walking in flat foot and so to recommend suitable backpack weight limitations for flat foot subjects. Method : 14 young flat foot subjects($24.29{\pm}2.16yrs$) participated in this study. the subjects were assigned to carry backpack load and there was four level walking modes : (1) unloaded walking(0%), (2) 10% body weight(BW) load, (3) 15% BW load and (4) 20% BW load. Repeated ANOVA was used to compare each region data of foot according to different backpack weight. Results : As backpack load became increased, the contact area of midfoot was significantly increased, and contact area of forefoot and rearfoot were significantly decreased. maximum pressure at each region during walking tended to be greater as the load increased, but a significant difference was found only for the heel medial and lateral regions Conclusion : Based on this data, the weight of backpack could influenced structure and function of the foot in flat foot.

• Journal of Korean Institute of Industrial Engineers
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• v.26 no.2
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• pp.110-116
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• 2000

The soft drink deliveries are made for a broad line of soft drink products by using a hand truck and the backpack mode of carriage. The workers usually deliver the beverages by backpack mode of carriage, because they feel safe with such a carrying method in stairways. In this study, the physiological workload of backpack carrying was investigated, especially focused on the effects of weight of load and carrying by the stairway. A laboratory experiment was conducted to measure heart rate and oxygen uptake during backpack carrying tasks, and an ergonomic guideline was proposed for such type of task based on the results of the experiment. Eight healthy male subjects performed the backpack carrying of 40kg and 60kg, (1) on the level ground, (2) upstairs and (3) downstairs. The result showed that the stairways caused the increased physiological cost, and that a carrying load of 60kg required significantly higher physiological cost as compared to carrying 40kg. Although backpack carrying has some advantages in the biomechanical aspect, it should be advised to carry a load of less than 40kg, since the task requires a very high physiological cost. During backpack carrying, it is also recommended for a delivery person to make more trips with a light load rather than to make less trips with a heavier load at one trip.

• Physical Therapy Korea
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• v.27 no.1
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• pp.45-52
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• 2020

Background: A backpack is available equipment for moving some objects. Most studies have found that the appropriate weight limit of backpack for students is between 10% to 15% of their body weight (BW). However, Some students should carry a backpack heavier than 15% of BW. Therefore, It is associated with abnormal shoulder and neck posture on students. Objects: This study tested the effects that various amounts of weight carried by university students in their backpacks had on their cervical posture and electromyography of neck muscle. Methods: The subjects consisted of 12 students (6 male, 6 female) in university. There were three loading conditions tested: no backpack, a backpack that weighed 10% and 15% of the student's BW. The dependent variables were the craniovertebral angle (tragus to C7) and the neck muscle activities (sternocleidomastoid, upper trapezius). All 12 subjects were asked to walk while wearing a backpack for 5 minutes and were then instructed to rest for 2 minutes. Results: When assessing the craniovertebral angle, the results of this study were significantly decreased in the order of 0%, 10%, and 15%. And then, there were significantly increased electromyography of neck muscles that comparison of the weight of 10% and 15% on 0%. It was found that as the weight of the backpack increased, the craniovertebral angle decreased (p < 0.05) and the muscle activities increased (upper trapezius p = 0.012, sternocleidomastoid p = 0.013). Conclusion: Our study recommended that some students shouldn't carry on over the 15% backpack of own weight, and also they should distribute backpack load to equal on body for optimal posture.

• Korean Journal of Applied Biomechanics
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• v.25 no.2
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• pp.191-198
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• 2015

Objective : The purpose of this study was to conduct biomechanical analysis of varying backpack loads on the lower limb movements during downhill walking over $-20^{\circ}$ ramp. Method : Thirteen male university students (age: $23.5{\pm}2.1yrs$, height: $175.7{\pm}4.6cm$, weight: $651.9{\pm}55.5N$) who have no musculoskeletal disorder were recruited as the subjects. Each subject walked over $20^{\circ}$ ramp with four different backpack weights (0%, 10%, 20% and 30% of body weight) in random order at a speed of $1.0{\pm}0.1m/s$. Five digital camcorders and two force plates were used to obtain 3-d data and kinetics of the lower extremity. For each trial being analyzed, five critical instants were identified from the video recordings. Ground reaction force, loading rate, decay rate, and resultant joint moment of the ankle and the knee were determined by the inverse dynamics analysis. For each dependent variable, one-way ANOVA with repeated measures was used to determine whether there were significant differences among four different backpack weight conditions (p<.05). When a significant difference was found, post hoc analyses were performed using the contrast procedure. Results : The results of this study showed that the medio-lateral GRFs at RHC in 20% and 30% body weight were significantly greater than the corresponding value in 0% of body weight. A consistent increase in the vertical GRFs as backpack loads increased was observed. The valgus joint movement of the knee at RTO in 30% body weight was significantly greater than the corresponding values in 0% and 10% body weight. The increased valgus moment of 30% body weight observed in this phase was associated with decelerating and stabilizing effects on the knee joint. The results also showed that the extension and valgus joint moments of the knee were systematically affected by the backpack load during downhill walking. Conclusion : Since downhill walking while carrying heavy external loads in a backpack may lead to excessive knee joint moment, damage can occur to the joint structures such as joint capsule and ligaments. Therefore, excessive repetitions of downhill walking should be avoided if the lower extremity is subjected to abnormally high levels of load over an extended period of time.

• Korean Journal of Applied Biomechanics
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• v.16 no.2
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• pp.25-35
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• 2006

The purpose of this study was to investigate the shock attenuation mechanisms while varying the loads in a backpack during drop landing. Ten subjects (age: $22.8{\pm}3.6$, height: $173.5{\pm}4.3$, weight: $70.4{\pm}5.2$) performed drop landing under five varying loads (0, 5kg. 10kg. 20kg. 30kg). By employing two cameras (Sony VX2100) the following kinematic variables (phase time, joint rotational angle and velocity of ankle, knee and hip) were calculated by applying 2D motion analysis. Additional data, i.e. max vertical ground force (VGRF) and acceleration, was acquired by using two AMTI Force plates and a Noraxon Inline Accelerometer Sensor. Through analysing the power spectrum density (PSD), drop landing patterns were classified into four groups and each group was discovered to have a different shock attenuation mechanism. The first pattern that appeared at landing was that the right leg absorbed most of the shock attenuation. The second pattern to appear was that subject quickly transferred the load from the right leg to the left leg as quickly as possible. Thus, this illustrated that two shock attenuation mechanisms occurred during drop landing under varying load conditions.

• Journal of the Korea Institute of Military Science and Technology
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• v.18 no.3
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• pp.309-315
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• 2015

This paper presents a lower-limb exoskeleton testbed and its control method. An exoskeleton is a wearable robotic system that can enhance wearer's muscle power or assist human's movements. Among a variety of its applications, especially for military purpose, a wearable robot can be very useful for carrying heavy loads during locomotion by augmenting soldiers' mobility and endurance. The locomotion test on a treadmill was performed up to maximum 4km/h walking speed wearing the lower-limb exoskeleton testbed with a 45kg backpack load.

• Korean Journal of Applied Biomechanics
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• v.27 no.2
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• pp.109-116
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• 2017

Objective: This study aimed to investigate the relationship between leg stiffness and kinematic variables according to load while running. Method: Participants included eight healthy men (mean age, $22.75{\pm}1.16years$; mean height: $1.73{\pm}0.01m$; mean body weight, $71.37{\pm}5.50kg$) who ran with no load or a backpack loaded with 14.08% or 28.17% of their body weight. The analyzed variables included leg stiffness, ground contact time, center of gravity (COG) displacement and Y-axis velocity, lower-extremity joint angle (hip, knee, ankle), peak vertical force (PVF), and change in stance phase leg length. Results: Dimensionless leg stiffness increased significantly with increasing load during running, which was the result of increased PVF and contact time due to decreased leg lengths and COG displacement and velocity. Leg length and leg stiffness showed a negative correlation (r = -.902, $R^2=0.814$). COG velocity showed a similar correlation with COG displacement (r = .408, $R^2=.166$) and contact time (r = -.455, $R^2=.207$). Conclusion: Dimensionless leg stiffness increased during running with a load. In this investigation, leg stiffness due to load increased was most closely related to the PVF, knee joint angle, and change in stance phase leg length. However, leg stiffness was unaffected by change in contact time, COG velocity, and COG displacement.

• Proceedings of the Korean Society of Computer Information Conference
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• 2013.07a
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• pp.149-151
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• 2013

본 연구의 목적은 휴대용 보병무기체계의 배낭 설계를 위하여 인체공학적인 물자취급 중량을 검토하는데 있다. 제품설계시 인체공학적 설계 가이드라인과 운용현황을 조사분석하여 효율적인 운용성능을 위한 기초자료를 제공하고자 한다. 기존의 설계 가이드라인을 분석한 결과, 병사의 인체사이즈 측면에서는 5%tile의 경우 -091kg으로 여유중량이 부족하지만, 95%tile에서는 34.17kg까지 여유중량이 발생하는 것으로 판단된다. 이러한 연구결과는 물자취급시 편하고, 효율적인 운용성능을 창출하기 위해서 휴대중량과 이동거리에 따라 여유중량을 관리해야 할 것으로 판단된다.

• The Journal of Korean Physical Therapy
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• v.21 no.3
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• pp.61-68
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• 2009

Purpose: The purpose of this study was to analyze the changes of the relative impulse of the foot when carrying 5 types of schoolbag during level walking. Methods: Forty-four normal subjects were divided into 5 groups according to the method of carrying a bag: carrying no bag (condition 1), a backpack (condition 2), a shoulder bag (condition 3), a cross bag (condition 4) and a one-hand bag (condition 5). To evaluate the partial relative impulse, 7 areas were measured on the sole of a foot: the hallux, toe, 1st metatarsal head (Met1) and the 2nd & 3rd metatarsal heads (Met2/3), the 4th & 5th metatarsal heads (Met4/5), mid foot and heel. Repeated one-way analysis of variance (ANOVA) and independent t-tests were used to analyze the statistical data. Results: In the right foot, the relative impulses in every areas revealed no significant difference (p>0.05), however, the relative impulses at Met1, Met2/3, Met4/5 and heel were significantly different between the different conditions (p<0.05). There were significant differences on comparing the relative impulse between left and right foot within one condition, the mid foot in condition 2, as well as the hallux and Met1 in condition 3 (p<0.05). In condition 4, the toe, Met1, Met4/5 and mid foot were significantly different (p<0.05). The values at the hallux, toe and Met1 in condition 5 also were significantly different (p<0.05). Conclusion: These findings showed that the symmetrical relative impulse of the foot was present in the case of carrying a backpack, but there was an extra load on specific regions and asymmetrical relative impulses in the case of carrying a shoulder bag, a across bag and a one-hand bag. (ED note: this abstract is not clear. You need to work on it.)

• Child Health Nursing Research
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• v.21 no.4
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• pp.320-330
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• 2015

Purpose: The purpose of this study was to investigate the use of schoolbags and the prevalence of musculoskeletal symptoms among elementary school children and to identify factors associated with relative schoolbag weight and musculoskeletal symptoms. Methods: A descriptive correlation study was conducted with 228 elementary school children in grades 4-6. A self-administered questionnaire was used for data collection. Descriptive statistics, t-test, ANOVA, $x^2$-test or Fisher's exact test, logistic regression analysis were used for data analysis. Results: Mean relative schoolbag weight (RSW) was 6.40%. Among participants, 13.2% carried more than 10% of their RSW. Only 49.6% of participants organized the contents in their school backpack correctly. Musculoskeletal symptoms were reported by 42.5% of participants. Results from logistic regression analysis identified grade was a significant factor predicting RSW, and gender, RSW, and using a locker were significant factors predicting musculoskeletal symptoms among schoolchildren. Conclusion: Although RSW of school children in this study was within the currently recommended load limit, a considerable proportion of school children were not following guidelines for safe schoolbag use. An effective schoolbag safety campaign for parents, students, and teachers needs to be developed and evaluated to prevent possible musculoskeletal symptoms related to schoolbag use.