Backpack Load Research Articles

Blood lactate thresholds and walking/running economy are determinants of backpack-running performance in trained soldiers

We developed a standardized laboratory treadmill protocol for assessing physiological responses to a simulated backpack load-carriage task in trained soldiers, and assessed the efficacy of blood lactate thresholds (LTs) and economy in predicting future backpack running success over an 8-mile course in field conditions. LTs and corresponding physiological responses were determined in 17 elite British soldiers who completed an incremental treadmill walk/run protocol to exhaustion carrying 20 kg backpack load. Treadmill velocity at the breakpoint (r = −0.85) and Δ 1 mmol l−1 (r = −0.80) LTs, and relative V˙O2 at 4 mmol l−1 (r = 0.76) and treadmill walk/run velocities of 6.4 (r = 0.76), 7.4 (r = 0.80), 11.4 (r = 0.66) and 12.4 (r = 0.65) km h−1 were significantly associated with field test completion time. We report for the first time that LTs and backpack walk/run economy are major determinants of backpack load-carriage performance in trained soldiers.

Reducing Dynamic Loads From a Backpack During Load Carriage Using an Upper Body Assistive Device

This paper presents studies of an upper body assistive device designed to aid human load carriage. The two primary functions of the device are: (i) distributing the backpack load between the shoulders and the waist and (ii) reducing the dynamic load of a backpack on the human body during walking. These functions are targeted to relieve stress applied on the shoulders and the back, and also reduce the dynamic loads transferred to the lower limbs during walking. These functions are achieved by incorporating two modules—passive and active—within a custom fitted shirt integrated with motion/force sensors, actuators, and a real-time controller. The relevant modeling and controller design are presented for dynamic load compensation. Preliminary evaluation of the device was first performed on a single subject, followed by a pilot study with ten healthy subjects walking on a treadmill with a backpack. Results show that the device can effectively transfer the load from the shoulders to the waist and also reduce the dynamic loads induced by the backpack during walking. Reduction in peak and total normal ground reaction forces, leg muscle activations, and oxygen consumptions was observed with the device. This suggests that the device can potentially reduce the risk of musculoskeletal injuries and fatigue on the lower limbs associated with carrying heavy loads and provide some metabolic benefits.

Multi-objective analysis for assessing simultaneous changes in regional spinal curvatures under backpack carriage in young adults

Change in sagittal spinal curvature from the neutral upright stance is an important measure of the heaviness and correctness of backpack use. As current recommendations, with respect to spinal profile, of backpack load thresholds were based on the significant curvature change in individual spinal region only, this study investigated the most critical backpack load by assessing simultaneously the spinal curvature changes along the whole spine. A motion analysis system was used to measure the curvature changes in cervical, upper thoracic, lower thoracic and lumbar regions with backpack load at 0, 5, 10, 15 and 20% of body weight. A multi-objective goal programming model was adopted to determine the global critical load of maximum curvature change of the whole spine in accordance with the maximum curvature changes of the four spinal regions. Results suggested that the most critical backpack load was 13% of body weight for healthy male college students.Practitioner Summary: As current recommendations of backpack load thresholds were based on the significant curvature change in individual spinal region only, this study investigated the backpack load by considering simultaneously the spinal curvature changes along the whole spine. The recommendation, in terms of the global critical load, was 13% of body weight for healthy male college students.

Effect of Magnitude of Backpack Load and Duration of Carriage on Pulmonary Function Parameters among Urban Young Adults of West Bengal, India: An Ergonomic Study

Background: The college students (18-25 years) compelled to carry backpack load and are susceptible to physiological stress. Acceptable load limit is 10-15% of Body Weight (BW) among children and adolescents. Pulmonary function is an important physiological parameter which governs the cumulative stress on the body. The relationship between backpack carriage and pulmonary function parameters has not been explicitly studied among young adults. Objectives: The study aimed to investigate the changes in Forced Vital Capacity(FVC), Forced Expiratory Volume in one second (FEV1) and Tiffeneau index (FEV1%) with different duration of carriage at the level of 15% and 10% load of BW compared to no load condition. Methods: Pulmonary function tests were performed using Mini Spir (software Winspiro PRO) at 0-1 min, 10-11 min, 15-16 min of carriage among males (n=13) and females (n=19) with 15% load of BW; females (n=10) with 10% load of BW. Repeated measures ANOVA and paired two tailed student’s t test were performed. Results: Repeated measures ANOVA revealed, there was significant difference in FVC and FEV1 at different durations, when females carried both 15% and 10% load of BW. While carrying 15% load of BW at 0-1 min,10-11 min,15-16 min, females showed significant difference in FEV1 (p=0.004; p=0.0001; p=0.0001, respectively), FVC (p=0.031; p=0.003; p=0.0002, respectively) and FEV1% (p=0.026; p=0.010; p=0.047, respectively); males showed significant difference in FEV1 at 15-16 min (p=0.044) compared to no load. Females carrying 10% load of BW showed significant difference in FEV1 at 0-1 min (p=0.027) and 15-16 min (p=0.020), FVC in 15-16 min (p=0.024) compared to no load. Obstructive pattern was observed among females (n=10) with increased load. Conclusion: Males must not carry 15% static load of BW for more than 15 min and females should carry load lower than 10% of BW.

Determination of Backpack Loading on 6 Minute Walk Distance in School Children of 7–13 Years of Age

Determination of Backpack Loading on 6 Minute Walk Distance in School Children of 7–13 Years of Age

The effect of mechanical strains in soft tissues of the shoulder during load carriage

Soldiers and recreational backpackers are often required to carry heavy loads during military operations or hiking. Shoulder strain appears to be one of the limiting factors of load carriage due to skin and underlying soft tissue deformations, trapped nerves, or obstruction of blood vessels. The present study was aimed to determine relationships between backpack weights and the state of loads in the shoulder׳s inner tissues, with a special focus on the deformations in the brachial plexus. Open-MRI scans were used for developing and then verifying a three-dimensional, non-linear, large deformation, finite element model of the shoulder. Loads were applied at the strap-shoulder contact surfaces of the model by pulling the strap towards the shoulder until the desired load was reached. Increasing the strap tensile forces up to a load that represents 35kg backpack resulted in gradual increase in strains within the underlying soft tissues: the maximal tensile strain in the brachial plexus for a 25kg backpack was 12%, and while carrying 35kg, the maximal tensile strain increased to 16%. The lateral aspect of the brachial plexus was found to be more vulnerable to deformation-inflicted effects than the medial aspect. This is due to the anatomy of the clavicle that poorly shields the plexus from compressive loads applied during load carriage, while the neural tissue in the medial aspect of the shoulder is better protected by the clavicle. The newly developed model can serve as a tool to estimate soft tissue deformations in the brachial plexus for heavy backpack loads, up to 35kg. This method will allow further development of new strap structures and materials for alleviating the strains applied on the shoulder soft tissues.

Changes to transtibial amputee gait with a weighted backpack on multiple surfaces

BackgroundModern prosthetic technology and rehabilitation practices have enabled people with lower extremity amputations to participate in almost all occupations and physical activities. Carrying backpack loads can be an essential component for many of these jobs and activities; however, amputee gait with backpack loads is poorly understood. This knowledge gap must be addressed in order to further improve an individual's quality of living through changes in rehabilitation programs and prosthesis development. MethodsTen male, unilateral, K4-level (ability or potential for prosthetic ambulation that exceeds basic ambulation skills, exhibiting high impact, stress, or energy levels), transtibial amputees completed ten walking trials at a self-selected pace on simulated uneven ground, ramp ascent, and ramp descent. Five trials were with a 24.5kg backpack load and five trials without. Temporal–spatial parameters and kinematic peak values for the ankle, knee, hip, pelvis, and trunk were collected and analyzed for differences between backpack conditions. FindingsEach surface had novel findings not found on the other surfaces. However differences in temporal–spatial parameters were congruent with the literature on able bodied individuals. Pelvis and trunk angular velocities decreased with the backpack. Hip flexion on both limbs increased during weight acceptance while wearing the backpack, a common adaptation seen in able-bodied individuals on level ground. InterpretationA 24.5kg backpack load can be accommodated by transtibial amputees at the K4 functional level. Future studies on load carriage and gait training programs should include incline and descent due to the increased difficulty. Rehabilitation programs should verify hip and knee flexor strength and work to reduce intact limb reliance.

Center of pressure and total force analyses for amputees walking with a backpack load over four surfaces

Understanding how load carriage affects walking is important for people with a lower extremity amputation who may use different strategies to accommodate to the additional weight. Nine unilateral traumatic transtibial amputees (K4-level) walked over four surfaces (level-ground, uneven ground, incline, decline) with and without a 24.5 kg backpack. Center of pressure (COP) and total force were analyzed from F-Scan insole pressure sensor data. COP parameters were greater on the intact limb than on the prosthetic limb, which was likely a compensation for the loss of ankle control. Double support time (DST) was greater when walking with a backpack. Although longer DST is often considered a strategy to enhance stability and/or reduce loading forces, changes in DST were only moderately correlated with changes in peak force. High functioning transtibial amputees were able to accommodate to a standard backpack load and to maintain COP progression, even when walking over different surfaces.

내림 경사로 보행시 배낭 무게에 따른 하지 움직임의 운동역학적 분석

Objective : The purpose of this study was to conduct biomechanical analysis of varying backpack loads on the lower limb movements during downhill walking over ramp. Method : Thirteen male university students (age: , height: , weight: ) who have no musculoskeletal disorder were recruited as the subjects. Each subject walked over ramp with four different backpack weights (0%, 10%, 20% and 30% of body weight) in random order at a speed of . 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

Effect of asymmetrical backpack load on spinal curvature in school children.

Carrying a backpack is common among schoolchildren. The effect of backpack load on spine pain and posture defects in children is often raised in the literature. According to scientific research, the maximum backpack load that is safe for children must not exceed 10-15% of their body mass. There is a lack of scientific reports related to the effect of frequently wearing a backpack on one shoulder among children and young adults and its influence on the shape of the anterior-posterior curvatures of spine. The aim of this study is to evaluate body posture parameters in the sagittal plane for an asymmetrical backpack load equal to 10% of a child's body mass. The study was conducted using 162 primary schoolchildren aged 11-13 years. Each participant underwent three tests that examined postural parameters, including habitual posture, with the backpack on the participant's right and left shoulder. Posture was measured with the CQ Elektronik; which uses photogrammetry to make anthropometric calculations based on an image of the examined surface. The asymmetrical backpack load resulted in a significant reduction of thoracic kyphosis (GKP: p=0.040). The angle of thoracic kyphosis increased between the measurements. The difference (GAMMA=0.054) revealed that the results were approaching significance. Considering the gravity of the problem, children should be educated on ergonomics by teachers, physiotherapist or nurses, including instructions on carrying a backpack and the effects of disregarding the basic rules on body posture, as part of their school curriculum. The acceptable backpack load, which is now believed to be 10% of the child's body mass, should be carefully considered by scientists. Our own results show that even a load of 10% of the body mass may induce negative changes in spinal posture.

평지 보행을 위한 하지 근력증강 로봇 테스트베드

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.

Shoulder skin and muscle hemodynamics during backpack carriage

The purpose of this study was to quantify the effects of loaded backpacks on shoulder muscle oxygenation, skin blood flow, and pain. We hypothesized that backpack load carriage is associated with lower shoulder muscle oxygenation and skin microvascular flow. Near-infrared spectroscopy quantified shoulder tissue oxygenation and laser Doppler flow measured skin microvascular flow. Eight adult volunteers donned a standard backpack without added load, 5 kg load, and 10 kg load for 5 min while standing. An 8 min rest period before each backpack donning condition ensured that all measured parameters returned to baseline. Data were analyzed using a repeated measures ANOVA and significance set at p < 0.05. Donning a 10 kg backpack significantly reduced shoulder muscle oxygenation by 22 ± 23% as compared to the empty backpack control condition (p = 0.023). In addition, a 10 kg backpack load reduced skin microvascular flow by 82 ± 22%, as compared to the empty backpack control condition (p = 0.024). Perceived pain was significantly higher when wearing the 10 kg backpack (level 4 on a 10-maximal pain scale) as compared to the empty backpack (0, 0–no pain) (p < 0.05). In conclusion, backpack loads of 10 kg decrease shoulder muscle oxygenation and skin microvascular flow.

Effects of load carriage and footwear on spatiotemporal parameters, kinematics, and metabolic cost of walking

Gait patterns are commonly altered when walking or running barefoot compared to shod conditions. Although controversy exists as to whether barefoot conditions result in lower metabolic costs, it is clear that adding load to the body results in increased metabolic costs. The effects of footwear and backpack loading have been investigated separately, but it is unclear whether manipulating both simultaneously would cause similar outcomes. Twelve healthy individuals (7 female, 5 male) with no obvious gait abnormalities participated in this study (age=24±2 years, height=1.73±0.13m, and mass=71.1±16.9kg). Steady state metabolic data and 3D motion capture were collected during treadmill walking at 1.5ms−1 in four conditions: Barefoot Unloaded, Shod Unloaded, Barefoot Loaded, and Shod Loaded. Barefoot walking elicited shorter stride lengths, stance and double support times, as well as a slight (≈1%), but not significant, decrease in metabolic cost. Loading increased metabolic costs of walking but did not elicit spatiotemporal changes in either footwear condition. Lower limb kinematic differences were noted in response to both loading and footwear. Changes in spatiotemporal parameters observed when walking barefoot were not exacerbated by the addition of a backpack load. This suggests that the increased metabolic demand associated with the load is met with a similar spatiotemporal pattern whether a person wears a supportive shoe or not. Thus, the discomfort associated with foot strike while barefoot that promotes spatiotemporal changes seems to be independent of load.

Effects of Backpack on Lower and Upper Body Reaching Ability

PURPOSE: Backpack carriage is well known to negatively affect metabolic performance during marching/hiking. However, reaching performance with lower and upper body has not been examined during load carriage with a backpack, yet this might be important during specific conditions. METHODS: Lower extremity reaching during backpack carriage was tested using the Y-Balance Test (a variation of the Star Excursion Balance Test measuring leg reach in posterolateral, posteromedial and anterior directions), and upper extremity reaching was tested using the Functional Reach Test (FRT). Subjects were healthy males (n=6) and females (n=6), ages 19-47, who wore a military (MOLLE II) backpack and performed in bare feet using the dominant leg and arm for reaching. During both tests, subjects were tested without the backpack, and then (in random order) with the backpack empty (0), or with a load of sand equivalent to 10, 30, and 50% of their bodyweight. Three trials were completed for each reach condition and the results averaged. Mean values were analyzed with paired t-tests and Bonferroni corrections. RESULTS: Data presented as mean reach in cm ± SD; * = sig diff from No backpack (p < 0.0125 t-test). Backpack load resulted in reductions in leg (lower body) reach in all three directions. Backpack load resulted in an increase in arm (upper body) reach at the heaviest (50%) load, although the empty backpack (0%) resulted in a decrease in arm (upper body) reach. CONCLUSIONS: Backpack loads of 10%-50% of an individual’s bodyweight decreased reach performance with the lower extremity, but increased upper extremity reaching with the heaviest load.Table: No title available.

Musculoskeletal stiffness changes linearly in response to increasing load during walking gait

Development of biologically inspired exoskeletons to assist soldiers in carrying load is a rapidly expanding field. Understanding how the body modulates stiffness in response to changing loads may inform the development of these exoskeletons and is the purpose of the present study. Seventeen subjects walked on a treadmill at a constant preferred walking velocity while nine different backpack loading conditions ranging from 12.5% to 40% bodyweight (BW) were introduced in an ascending and then descending order. Kinematic data were collected using Optotrak, a 3D motion analysis system, and used to estimate the position of the center of mass (COM). Two different estimates of stiffness were computed for the stance phase of gait. Both measures of stiffness were positively and linearly related to load magnitudes, with the slopes of the relationships being larger for the descending than the ascending conditions. These results indicate that changes in mechanical stiffness brought about in the musculoskeletal system vary systematically during increases in load to ensure that critical kinematic variables measured in a previous publication remain invariant (Caron et al., 2013). Changes in stiffness and other kinematics measured at the 40% BW condition suggest a boundary in which gait stiffness control limit is reached and a new gait pattern is required. Since soldiers are now carrying up to 96% of body weight, the need for research with even heavier loads is warranted. These findings have implications on the development of exoskeletons to assist in carrying loads.

The muscle activation patterns of lower limb during stair climbing at different backpack load.

Stair climbing under backpack load condition is a challenging task. Understanding muscle activation patterns of lower limb during stair climbing with load furthers our understanding of the factors involved in joint pathology and the effects of treatment. At the same time, stair climbing under backpack load requires adjustments of muscle activations and increases joint moment compared to level walking, which with muscle activation patterns are altered as a result of using an assistive technology, such as a wearable exoskeleton leg for human walking power augmentation. Therefore, the aim of this study was to analyze lower limb muscles during stair climbing under different backpack load. Nine healthy volunteers ascended a four-step staircase at different backpack load (0 kg, 10 kg, 20 kg, 30 kg). Electromyographic (EMG) signals were recorded from four lower limb muscles (gastrocnemius, tibialis anterior, hamstring, rectus femoris). The results showed that muscle activation amplitudes of lower limb increase with increasing load during stair climbing, the maximum RMS of gastrocnemius are greater than tibialis anterior, hamstring and rectus femoris whether stair climbing or level walking under the same load condition. However, the maximum RMS of hamstring are smaller than gastrocnemius, tibialis anterior and rectus femoris. The study of muscle activation under different backpack load during stair climbing can be used to design biomechanism and explore intelligent control based on EMG for a wearable exoskeleton leg for human walking power augmentation.

The effects of backpack loads and spinal stabilization exercises on the dynamic foot pressure of elementary school children with idiopathic scoliosis.

[Purpose] The purpose of this study was to measure and observe the changes in dynamic plantar pressures when school children carried specific bag loads, and to determine whether improved physical balance after an eight-week spinal stabilization exercise program can influences plantar pressures. [Subjects] The subjects were 10 school students with Cobb angles of 10° or greater. [Methods] Gait View Pro 1.0 (Alfoots, Korea) was were based on to measure the pressure of the participants’ feet. Spinal stabilization exercises used TOGU Multi-roll Functional (TOGU, Germany) training. Dynamic plantar pressures were measured with bag loads of 0% no bag and 15% of subjects’ body weight. The independent t test was performed to analyze changes in plantar pressures. [Results] The plantar pressure measurements of bag load of 0% of subjects’ body weight before and after the spinal stabilization exercise program were not significantly different, but those of two foot areas with a 15% load were statistically significant (mt5, 67.32±24.25 and 51.77±25.52 kPa; lat heel, 126.00±20.46 and 102.08±23.87 kPa). [Conclusion] After performance of the spinal stabilization exercises subjects’ overall plantar pressures were reduced, which may suggest that physical balance improved.

Body posture and backpack loading: an upright magnetic resonance imaging study of the adult lumbar spine

Axial loading of the spine while supine, simulating upright posture, decreases intervertebral disc (IVD) height and lumbar length and increases lumbar lordosis. The purpose of this study is to measure the adult lumbar spine's response to upright posture and a backpack load using upright magnetic resonance imaging (MRI). We hypothesize that higher spinal loads, while upright and with a backpack, will compress lumbar length and IVD height as well as decrease lumbar lordosis. Six volunteers (45 ± 6 years) underwent 0.6 T MRI scans of the lumbar spine while supine, upright, and upright with a 10 % body weight (BW) backpack. Main outcomes were IVD height, lumbar spinal length (distance between anterior-superior corners of L1 and S1), and lumbar lordosis (Cobb angle between the superior endplates of L1 and S1). The 10 % BW load significantly compressed the L4-L5 and L5-S1 IVDs relative to supine (p < 0.05). The upright and upright plus 10 % BW backpack conditions significantly compressed the anterior height of L5-S1 relative to supine (p < 0.05), but did not significantly change the lumbar length or lumbar lordosis. The L4-L5 and L5-S1 IVDs compress, particularly anteriorly, when transitioning from supine to upright position with a 10 % BW backpack. This study is the first radiographic analysis to describe the adult lumbar spine wearing common backpack loads. The novel upright MRI protocol described allows for functional, in vivo, loaded measurements of the spine that enables the study of spinal biomechanics and therapeutic interventions.

RISK OF INTERVERTEBRAL DISC DAMAGE AFTER PROLONGED SPACE FLIGHT

BackgroundBack pain and intervertbral disc (IVD) damage are common problems experienced by astronauts. We hypothesize this is from paraspinal muscle deconditioning, ∼5 cm body lengthening from spinal swelling and straightening,...

Altered Disc Compression in Children With Idiopathic Low Back Pain

This study is a repeated measures design to measure the lumbar spine's response to common backpack loads in children with idiopathic low back pain (ILBP) using upright magnetic resonance imaging (MRI). The purpose of this study is to analyze the lumbar spine's response to backpack loads with upright MRI in children with ILBP to compare their results with previously published normal child data under the same conditions. We hypothesize that typical backpack loads will have a different effect on the lumbar spine of normal children and children with ILBP. Research in normal children shows that backpack loads compress the lumbar intervertebral discs (IVDs), increase lumbar coronal deformity, and increase pain. Fifteen pediatric and adolescent patients with ILBP were selected. Patients were excluded if a spinal deformity, an underlying pathology, or known injury was identified. A 0.6-T upright MRI scanner imaged the subjects while in supine and standing positions wearing 0-kg, 4-kg, and 8-kg backpacks. IVD height, lumbar lordosis, lumbar coronal deformity, and pain score were recorded after each condition and compared using analysis of variances. We compared the above-mentioned variables between ILBP and normal subjects using generalized least squares models. The cohort's mean age was 13 ± 3 years. The 4-kg and 8-kg backpacks only compressed the L5-S1 IVD relative to upright with no load. Subjects experienced increasing pain with increasing load. Load had no effect on lumbar lordosis or lumbar coronal deformity. Compared with normal children, children with ILBP experience significantly less disc compression at T12-L1 to L4-L5, less lumbar lordosis, and more pain with increasing load. In children with ILBP, increasing backpack load compresses only the L5-S1 IVD. Compared with normal children, children with ILBP experience less lumbar IVD compression, less lumbar lordosis, and more pain due to increasing load suggesting altered mechanisms for load tolerance in children with ILBP. 3.