Backpack Carriage Research Articles

Increase in Leg Stiffness Reduces Joint Work During Backpack Carriage Running at Slow Velocities.

Optimal tuning of leg stiffness has been associated with better running economy. Running with a load is energetically expensive, which could have a significant impact on athletic performance where backpack carriage is involved. The purpose of this study was to investigate the impact of load magnitude and velocity on leg stiffness. We also explored the relationship between leg stiffness and running joint work. Thirty-one healthy participants ran overground at 3 velocities (3.0, 4.0, 5.0 m·s-1), whilst carrying 3 load magnitudes (0%, 10%, 20% weight). Leg stiffness was derived using the direct kinetic-kinematic method. Joint work data was previously reported in a separate study. Linear models were used to establish relationships between leg stiffness and load magnitude, velocity, and joint work. Our results found that leg stiffness did not increase with load magnitude. Increased leg stiffness was associated with reduced total joint work at 3.0 m·s-1, but not at faster velocities. The association between leg stiffness and joint work at slower velocities could be due to an optimal covariation between skeletal and muscular components of leg stiffness, and limb attack angle. When running at a relatively comfortable velocity, greater leg stiffness may reflect a more energy efficient running pattern.

The Effect of a Backpack Hip Strap on Energy Expenditure While Walking.

Objective To examine the effect of backpack hip strap use on walking energy expenditure while carrying a loaded backpack. Background Previous studies have demonstrated that energy cost increases as the mass of the load carried increases. However, few investigations have focused on backpack carriage design. Methods Fifteen young, healthy, male subjects walked at a self-selected pace for 10 minutes in two backpack loading conditions: with a hip strap (strapped) and without a hip strap (nonstrapped). Oxygen consumption (VO2), rating of perceived exertion (RPE), respiratory exchange ratio (RER), and heart rate (HR) were monitored throughout each 10-minute trial. Change scores from the 4th to 10th minute were calculated for each variable. A t test was used to evaluate the difference between conditions for each variable. Results The changes in VO2 (-0.62 ± 0.40 vs. 0.33 ± 0.23, p = .04) and RPE (1 ± 0.25 vs. 2 ± 0.21, p < .01) from the 4th to the 10th minute were different for the strapped versus nonstrapped condition. There was no difference in the change in RER (0.04 ± 0.01 vs. 0.03 ± 0.01, p > .05) or HR (3.53 ± 0.93 vs. 4.07 ± 1.39, p > .05) for the strapped versus unstrapped condition. Conclusions Wearing a hip strap reduced the energy expenditure and perceived exertion in as little as 10 minutes of walking compared to the nonstrapped condition. Future work should consider the effect of a hip strap on these variables while hiking for extended periods. Application Wearing a hip strap may increase the comfort and reduce the energy required of wearing a backpack. This is useful information for backpack designers, military personnel, and recreational hikers.

Effects of backpack load on critical changes of trunk muscle activation and lumbar spine loading during walking

This study investigated the effects of carrying a backpack while walking. Critical changes featuring the disproportionality of increases in trunk muscle activation and lumbar joint loading between light and heavy backpack carriage weight may reveal the load-bearing strategy (LBS) of the lumbar spine. This was investigated using an integrated system equipped with a motion analysis, a force platform and a wireless surface electromyography (EMG) system to measure the trunk muscle EMG amplitudes and lumbar joint component forces. A predictive goal programming model was developed to determine the most critical changes in trunk muscle activation and lumbar joint loading. Results suggested that lightweight backpack carriage at approximately 3% of body weight (BW) might reduce the peak lumbosacral compression force by 3% during walking compared with no load condition. The most critical changes in both trunk muscle activation and lumbosacral joint loading were found at a backpack load of 10% of BW.Practitioner Summary: This study investigated the effects of backpack load on the LBS of lumbar spine while walking. A backpack load of 3% of BW might reduce the peak lumbosacral compression force by 3 and 10% of BW induced the most critical changes in LBS of lumbar spine.

Immediate responses to backpack carriage on postural angles in young adults: A crossover randomized self-controlled study with repeated measures.

Heavy backpacks have been associated with various postural changes and consequently musculoskeletal disorders. We evaluated the immediate responses of varying backpack loads on cranio-vertebral angle (CVA), sagittal shoulder angle (SSA) and trunk forward lean (TFL) of young adults between the ages of 18-25 years. This was a 3×3 cross over randomized controlled study with repeated measures among a convenience sample of young adults (n = 30; 50% male, 50% female). Each participant in a standing posture was assessed at four different loads: no backpack, carrying backpack of 5%, 10%, and 15% of body weight (BW). A sagittal photograph was taken of the area of the body corresponding to spinal angle during each of these test conditions to allow for later analysis of postural deviations. Comparisons of the mean deviations of the different postural angles from baseline and between test conditions were made using ANOVA at p≤0.05. Generally, there was a trend toward a decrease in the CVA and TFL with increasing backpack loads. Specifically, a significant decrease was seen for TFL at10% and 15% BW loads when compared with no load condition. In contrast, the decrease in CVA was only significant between no load condition and 15% body weight load. The SSA remained unchanged with backpack weight within 15% BW. Whereas the SSA of young adults may not be upset by an acute loading with a backpack within 15% of body weight, a 15% BW backpack led to more forward posture of the head on the neck. In addition, backpack load as low as 10% BW is enough to cause an immediate forward lean of the trunk.

Loading of the lumbar spine during backpack carriage

Backpack carriage is significantly associated with a higher prevalence of low back pain. Elevated compression and shear forces in the lumbar intervertebral discs are known risk factors. A novel method of calculating the loads in the lumbar spine during backpack carriage is presented by combining physical and numerical modelling. The results revealed that to predict realistic lumbar compression forces, subject-specific lumbar curvature data were not necessary for loads up to 40 kg. In contrast, regarding shear forces, using subject-specific lumbar curvature data from upright MRI measurements as input for the rigid body model significantly altered lumbar joint force estimates.

Effect of Backpack Strap Patterns on Gait Parameters in Young Adults at Self-Selected Normal and Fast Walking Speeds

BackgroundThe effects of backpack load on young adults’ gait parameters have received little attention. We previously reported that with a backpack load within 15% body weight (BW), young adults maintain their gait parameters at the expense of increased exertion during a 6-minute walk at self-selected normal walking speed. However, the effect of backpack strap pattern on gait parameters during faster walking or longer stride length has not been evaluated. ObjectiveTo determine the effect of different backpack strap patterns on gait parameters during a 12-minute walk test in young adults at self-selected normal and fast walking speeds. DesignA crossover, self-controlled experimental study with repeated measures. SettingDepartment of Medical Rehabilitation, University of Nigeria. ParticipantsA convenience sample of 24 healthy young adults (21.29 ± 1.20 years) who voluntarily signed an informed consent form, were able to wear a backpack on 1 and on both shoulders, were able to walk independently, and passed the physical activity readiness screening participated in this study. MethodsUsing a validated method of an observational gait analysis, each participant carried out a 12-minute walk test at self-determined normal and fast walking speeds, respectively. The effect of the following test conditions on the selected gait parameters was evaluated: normal and fast walking without load, and normal and fast walking with 10% and 20% BW backpack carried each on 1 and both shoulders. Main Outcome MeasurementStride length, stride time, velocity, cadence, and base of support were assessed by the equation definitions method of the velocity field diagram. ResultsAt self-selected fast walking speed with 10% BW backpack load, stride time (P = .004) and cadence (P = .006) were significantly decreased when participants wore a double-strap backpack. At self-selected normal walking speed with 20% BW backpack load, cadence was significantly decreased with double-strap backpack carriage (P = .008). Cadence (P < .001), velocity (P < .001), and stride time (P < .001)were also significantly decreased at both conditions of single and double-strap backpack carriage of 20% BW respectively at fast walking speed. ConclusionBackpack strap patterns do not affect the gait parameters of young adults in a 12-minute bout of normal walking speed, provided that the load is less than 20% BW. However, a load up to 10% BW carried on a double strap causes a decrease in stride time and cadence when these individuals walk fast. Level of EvidenceNot applicable.

The Effect of Backpack Carriage on the Biomechanics of Walking: A Systematic Review and Preliminary Meta-Analysis.

The aim of this systematic review was to evaluate the impact of bilaterally symmetrical backpack systems borne on the posterior trunk on walking biomechanics, as backpacks represent the most prevalent method of load carriage in the military and civilian population. A search of electronic databases was performed for studies that only investigated posteriorly-borne backpack carriage during level-grade walking (treadmill and over ground). Methodology of studies was assessed, and both meta-analysis and qualitative synthesis were completed. Fifty-four studies were included in this review. In summary, the available literature showed that backpack carriage in walking was associated with an increased trunk flexion angle, increased hip and ankle range of motion, increased vertical and horizontal ground reaction force, increased cadence, and reduced stride length. Several variations in backpack carriage protocols could explain between-study variations in results, including: walking speed, backpack carriage skill level, the use of a hip belt, and posterior displacement of the load away from the trunk. The findings of this systematic review will inform backpack carriage practices in the area of injury risk assessment and physical performance enhancement.

Effects of Backpack Carriage on Dual-Task Performance in Children During Standing and Walking

ABSTRACTPrimary school children perform parts of their everyday activities while carrying school supplies and being involved in attention-demanding situations. Twenty-eight children (8–10 years old) performed a 1-legged stance and a 10 m walking test under single- and dual-task situations in unloaded (i.e., no backpack) and loaded conditions (i.e., backpack with 20% of body mass). Results showed that load carriage did not significantly influence children's standing and walking performance (all p > .05), while divided attention affected all proxies of walking (all p < .001). Last, no significant load by attention interactions was detected. The single application of attentional but not load demand negatively affects children's walking performance. A combined application of both did not further deteriorate their gait behavior.

Analyzing the potential benefits ofusingabackpack with non-flexible straps.

Conventional backpack straps are flexible. Due to this flexibility, backpacks freely move on the human back. In this study, a new design of backpacks with non-flexible straps is proposed. The aim of the present research is to demonstrate the possible differences between normal gait and steps while participants carry two different backpacks. In this investigation, 9 healthy male college students were recruited with mean age, height and weight of 24.6 years, 179.6 cm and 76.41 kg, respectively. Each backpack was tested in two different steps. First, the participants were asked to walk on a treadmill, whose velocity was changed from 1.5 m/s to 2.5 m/s, for 15 minutes. Initial velocity was 1.5 m/s and the velocity increased 0.5 m/s in 5 minutes increments. In the next step, they walked for 15 minutes with constant velocity of 3 m/s. Head, neck, and trunk flexion or extension, lateral displacement, and velocity of the subjects during backpack carriage were compared with the obtained values during normal gait, when they walked without carrying a backpack. In addition, the level of discomfort (3 grades: Low, medium, severe) in the neck, shoulder, lumbar, upper and lower leg muscles were investigated by using a modified standardized questionnaire. By wearing the modified design of backpack, trunk flexion decreased while there was no significant (p > 0.05) change in velocity and lateral displacement. According to the questionnaire reports, more than 80% of the participants believed that both backpack discomfort in the neck (anterior side) and upper and lower legs were low. More than 75% of the subjects believed that by using a modified backpack, discomfort decreased for muscles in the neck (posterior), shoulder (posterior) and lumbar muscles. About 60% of both backpack users reported low discomfort in anterior shoulder muscles. Backpacks cause some bad effects on kinematics of gait. In this study, by testing modified backpacks, some improvements were seen, specifically in posture, which may be useful to reduce side effects of backpack carrying.

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.

Use of a backpack alters gait initiation of high school students

We assessed how backpack carriage influences the gait initiation (GI) process in high school students, who extensively use backpacks. GI involves different dynamics from gait itself, while the excessive use of backpacks can result in adverse effects. 117 high school students were evaluated in three experimental conditions: no backpack (NB), bilateral backpack (BB), and unilateral backpack (UB). Two force plates were used to acquire ground reaction forces (GRFs) and moments for each foot separately. Center of pressure (COP) scalar variables were extracted, and statistical parametric mapping analysis was performed over the entire COP/GRFs time series. GI anticipatory postural adjustments (APAs) were reduced and were faster in backpack conditions; medial–lateral COP excursion was smaller in this phase. The uneven distribution of the extra load in the UB condition led to a larger medial–lateral COP shift in the support-foot unloading phase, with a corresponding vertical GRF change that suggests a more pronounced unloading swing foot/loading support foot mechanism. The anterior–posterior GRFs were altered, but the COP was not. A possible explanation for these results may be the forward trunk lean and the center of mass proximity of the base of support boundary, which induced smaller and faster APA, increased swing foot/support foot weight transfer, and increased load transfer to the first step.

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.

The effect of backpack carriage on the biomechanics and neuromuscular control of locomotion: A systematic review and preliminary meta-analysis

The effect of backpack carriage on the biomechanics and neuromuscular control of locomotion: A systematic review and preliminary meta-analysis

School-based screening of plantar pressures during level walking with a backpack among overweight and obese schoolchildren

Among children, postural modifications due to backpack carriage have direct consequences on how forces are exchanged between body and ground and thus on plantar pressure distribution. However, it is unknown whether such alterations are influenced by the foot structure and functionality typical of obesity. In this study, we tested 65 overweight/obese primary schoolchildren using a pressure platform while walking with and without the backpack. Contact areas, arch index, peak and mean plantar pressures in the forefoot, midfoot and rearfoot were compared with those from an additional 65 age- and gender-matched group of normal-weight children. Backpack carriage modified pressure distribution similarly in both groups, with the exception of mean midfoot pressure, which increased significantly among normal-weight children but not in the overweight/obese group. Notably, the pressure values associated with mass excess and backpack carriage still raise some concerns regarding potential long-term adverse consequences on foot structure and functionality of overweight/obese children.Practitioner summary:Backpack carriage by overweight/obese schoolchildren altered plantar pressures similar to what was observed in their normal-weight peers. Yet, high pressures were found among the overweight/obese children. This raises concerns regarding potential long-term adverse consequences on foot structure and functionality, and supports establishing more specific limits for the carried load.

Backpack carriage effect on head posture and ground reaction forces in school children.

Carrying the school bag may lead to forward leaning of the head and trunk which may result in spinal deformities. The purpose of this study was to evaluate the effect of carrying a backpack on neck angles and ground reaction forces (GRFs) in children. 3-D motion analysis system, with a force plate, was used to examine the effect of carrying backpack on neck angles and GRFs of thirty children with mean age (10.06 ± 1.31 years), mean weight (34.56 ± 6.9 kg), and mean height (138.63 ± 9.82 cm). The unloaded posture was compared with posture when carrying a backpack. The static test was used to assess the three angles of the neck, and the dynamic test was used to assess the GRFs. There were no significant differences in the craniohorizontal angle and shoulder sagittal posture between carrying backpack and without backpack (p = 0.153 and 0.272) respectively. There was a significant decrease in the craniovertebral angle in carrying backpack than without backpack (p = 0.032). There was a significant increase in GRFs values in carrying backpack than without backpack (p < 0.032). Carrying backpack with a load 7.5% of the child's body weight alters the head posture and GRFs values.

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 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.

Short-term effects of backpack carriage on plantar pressure and gait in schoolchildren

PurposeTo assess the effects of backpack carriage on plantar pressure distributions and spatio-temporal gait parameters among children. ParticipantsTwo hundred-eighteen schoolchildren, aged 6–13, and attending primary and secondary schools in the city of Cagliari (Italy). MethodsParticipants were tested at school, during regular days. A pressure plate and wearable inertial sensors were used to measure plantar pressures and spatio-temporal parameters of gait. Measures were obtained during both quiet standing and walking, and both with and without a backpack. The latter contained those items a child had on the testing day. ResultsParticipants carried a mean mass in their backpacks of 5.2kg, and more than half had a backpack/body mass ratio higher than 15%. While spatio-temporal gait parameters were not affected by backpack carriage, significant increases (up to 25%) in plantar pressures were found during both static standing and walking, especially in the forefoot. ConclusionUnder realistic conditions, the impact of backpack carriage was more evident on foot-ground interaction than on gait features. However, long-term consequences of altered plantar pressure need to be assessed in future work, considering the actual durations typically spent carrying school items.

Effects of backpack carriage on lumbopelvic control: A dynamical systems analysis

Although heavy backpack carriage has been associated with back pain in schoolchildren, its causal relationship is still unknown. As people with low back pain exhibit an abnormal spinal control and backpack carriage has been shown to affect spinal repositioning ability in static upright stance, the goal of this study is to use dynamical systems theory to investigate the effects of backpack carriage on lumbopelvic control under dynamic situation. Lumbopelvic coordination was quantified in terms of Mean Absolute Relative Phase (MARP) and Deviation Phase (DP) whilst performing a reaching task under four loading conditions, i.e. no load, carrying 5%, 10% and 15% bodyweight (BW). It was shown that inter-segmental coordination was less in-phase (i.e. significant reduction in MARP with p < 0.001) and more variable (i.e. significant increase in DP with p = 0.005) during backpack carriage of 10% and 15% BW in forward reaching movement, suggesting greater alteration in lumbopelvic coordination at heavier weights. As abnormal movement strategies tend to increase the risk of spinal injury, pragmatic approaches should be considered to eradicate the adverse effect of heavy backpack carriage on spinal proprioception. Relevance to industryAdverse effects of backpack carriage on lumbopelvic control were demonstrated. Greater alteration in trunk control at heavier weights was shown. Strategies should be devised to eradicate the effects of backpack carriage on proprioception.

Alterations in the Plantar Pressure Patterns of Overweight and Obese Schoolchildren Due to Backpack Carriage

Among other adverse consequences, childhood obesity is known to influence foot structure and functionality. Yet little information is available regarding how the physiologic foot-ground interaction is altered when a localized load is carried, as occurs in the case of schoolbags. We investigated plantar contact area and pressure modifications induced by backpack carriage under actual conditions. We hypothesized that a localized load acting on the body would further increase the already excessive plantar pressure that exists with overweight and obese status. Seventy overweight and obese schoolchildren aged 6 to 11 years underwent two 30-sec trials on a pressure platform during a regular school day, with and without a backpack. Total and subregion contact areas along with peak plantar pressures were obtained, and results were compared with those of an equal-numbered group of normal-weight schoolchildren. Overweight and obese children generally had larger contact areas and higher peak plantar pressures compared with their normal-weight peers. In overweight and normal-weight participants, the backpack induced a similar generalized increase in contact area and pressures. However, the largest changes were observed in the forefoot, suggesting that load action tends to modify the physiologic pressure patterns. Backpack carriage raises the already elevated peak plantar pressures in overweight children during upright stance and modifies the physiologic pressure patterns. Further investigations are needed to clarify the features of such phenomenon when dynamic activities are performed and to verify the existence of fatigue and overexertion on the foot as well as other possible negative long-term effects.