Children require less gait kinematic adaptations to pull a trolley than to carry a backpack

The Influence of the Weight of the Backpack on the Biomechanics of the Child and Adolescent: A Systematic Review and Meta-analysis With a Meta-Regression

PURPOSE

To evaluate and explore the influence of the weight of a backpack on standing posture and gait in children and adolescents.

METHODS

We conducted a search of MEDLINE (PubMed), Cochrane Library, Cumulative Index to Nursing and Allied Health Literature (CINAHL), and Web of Science, with the last search in July 2021. Standardized mean differences (SMD) and 95% confidence intervals were calculated for relevant outcomes and were pooled in a meta-analysis using the random-effects model. The participants were healthy children or adolescents. The outcomes were postural variables, spatiotemporal gait variables, gait kinematics, and muscle activity. We analyzed the influence of a loaded backpack on posture while standing and spatiotemporal and kinematic variables while walking. We used GRADE, Risk of Bias 2, ROBINS-I, MINORS, and PEDro scales to rate the quality, certainty, and applicability of the evidence.

RESULTS

Wearing a loaded backpack induces a significant increase of the craniohorizontal angle while standing and a decrease of walking speed and stride length while walking. Only the craniovertebral angle had a significant relationship with the weight of the backpack.

CONCLUSIONS

Wearing a backpack induces postural changes while standing and affects gait in children and adolescents; however, almost all the changes are not related to the backpack weight.

Effects of backpack-induced fatigue on gait ground reaction force characteristics in primary school children with flat-foot deformity

This study aimed to assess the effects of backpack carriage in different weights and muscle fatigue on the GRF components in primary school children with flat-foot deformity. The GRF components from 42 primary school children (21 with low arch, and 21 with normal) were collected before and after backpack-induced fatigue protocol during shod walking with backpacks in weight 7.5, 10, 12.5 and 15% of the child's bodyweight. The amplitudes of Fx2 of 10%BW and Fz3 of 7.5%BW in the flatfeet group were less than in the healthy group without fatigued condition. (P < 0.05). After fatiguing, the amplitudes of Fx2 of 7.5%BW, Fz3 of 12.5 and 15%BW were significantly decreased in the low arch group than those in the healthy subjects (P < 0.05). Within-group comparisons of measured Fx2 of 10%BW, Fy1 (7.5,10 and 15%BW), Fy2 of 7.5%BW, FZ1 (7.5,10 and 15%BW), FZ2 (7.5,10 and 15%BW), and TTP of TFz1 of 7.5%BW, TFz3 (7.5,10 and 12.5%BW), Loading rate (7.5,10 and 15%BW) were significantly different from pre- to post-fatigue in the flatfeet group(P < 0.05). Within-group comparisons of measured Fy1 of 10%BW, Fy2 (7.5% and 10%BW), FZ1 (7.5% and 10%BW), FZ2 (7.5% and 10%BW), and TTP of TFz3 of 7.5%BW, Loading rate (7.5% and 10%BW) were significantly different from pre- to post-fatigue in the healthy group (P < 0.05). It seems that TTP of GRF variables does have clinical importance for rehabilitation of flatfeet deformity. Carrying heavy backpacks and backpack-induced fatigue had different effects on GRF characteristics among children with low and normal foot arch.

A Thorax Marker Set Model to Analyse the Kinematics of Walking Without the Need to Place Markers on the Back

BACKGROUND

Previous thorax models have been proposed for gait analysis, however these require markers to be placed on the back. This presents a limitation in the kinematic analysis of the thorax under load carriage conditions.

RESEARCH QUESTION

This study evaluated the validity and reliability of a thorax marker set that does not require markers to be placed on the back (HubemaLab model) when compared to 3 previously published marker set models.

METHODS

17 young adults were evaluated while walking at their self-selected speed. A 12 camera motion capture system was used to acquire the marker position data which was then processed using the respective models using Visual-3D. The level of agreement for the flexion/extension peak, right/left lateral peak and right/left rotation peak of the thorax angle and angular velocity; together with the range of motion and thorax angular velocities in the three planes was found between each thorax marker set, while the reliability was measured using the intraclass correlation coefficient.

RESULTS

The ICC results for the thorax angle ROM and the range of thorax angular velocity between the HubemaLab model and the other models showed excellent to good reliability in all three planes. While the ICCs for the peak flexion/extension, peak right/left lateral flexion and peak right/left rotation showed excellent to moderate reliability in all three planes.

CONCLUSION

The new model could be potentially valuable for kinematic gait analysis under load carriage conditions which obscure markers placed on the back.

Does a standard school trolley fit children of different heights?

Although school trolleys are an alternative to traditional backpacks, no studies have determined their suitability for children of different heights. This study aims to analyse the fit of a school trolley (0.89 m height from the top to the bottom of the handle) for children with different heights based on kinematic variables and the rate of perceived effort (RPE). A 3D motion capture system was used to analyse the kinematics of the thorax and hip during walking without load and when pulling a trolley loaded with 15% of the child's body weight (BW). The RPE was recorded at the end of each trial. The height of the subjects was clustered using Ward´s hierarchical cluster, and two groups were identified: Group 1: 120-139.9 cm; and Group 2: 140-160 cm. No differences were found between groups in the kinematics or RPE. In conclusion, a standard school trolley fits well to children with heights from 120 to 160 cm. Practitioner Summary: No studies have determined the suitability of school trolleys for children of different heights. This study aims to analyse the fit of a school trolley for children with different heights based on the kinematics and rate of perceived effort. The major finding is that a standard school trolley fits children with heights from 120 to 160 cm well and that the height of the school trolley was between 59% and 68% of the children's heights. Abbreviations: RPE: rate of perceived exertion; BW: body weight; CAST: calibrated anatomical system technique; GC: gait cycle.

Does schoolbag carriage equally affect obese/overweight and healthy-weight children?

Discrepancies exist in backpack load recommendations for obese/overweight children, and the recommendations do not consider school trolleys. This study analysed obese/overweight and healthy-weight students' perceived load and fatigue when carrying schoolbags and their gait kinematics and rate of perceived exertion (RPE) when carrying backpacks or pulling school trolleys with different loads. Twelve obese/overweight and 36 healthy-weight students were asked about their perceived load and fatigue in carrying their schoolbags to school. Then, a kinematic gait analysis was completed in students walking unloaded or transporting 10%, 15% or 20% of their bodyweight (BW) in a backpack or trolley. RPE was recorded after each condition. The average hip rotation and knee adduction angles differed between body mass index (BMI) groups. The healthy-weight group reported higher RPEs than the overweight/obese group when pulling a trolley with 10-15% BW. In conclusion, both BMI groups responded similarly to load and schoolbag type.

Development and Experimental Verification of an Ergonomic Backpack

Carrying a heavy school backpack has extensively been reported as a prime cause of children's body strain. It is suggested that the load should not exceed 10 percent of the child's body weight; however, ensuring this requires continuous monitoring. The study explores how ergonomically designed school backpack based on the user anthropometric data (n = 280) and ergonomic parameters help reduce force concentration on shoulders and back. It provides a validation process of the developed prototype by experimental verification. The developed design was assessed in a comparison experiment with a commercially available local school backpack. An experimental study was used which recruited thirty healthy college students (aged 19 to 23 years). Two independent variables evaluated were school backpack type (developed backpack versus commercial one) and load levels as a percentage of body weight. Three load levels were employed 10%, 15%, and 20%. These variables were measured on the responses: bag comfort scale and the percent of maximum voluntary contraction (%MVC) of six muscles (right and left of erector spine, right and left of external abdominal oblique muscle, and right and left of trapezius). The developed backpack provided astonishing performance at levels of 15% and 20% of body weight in terms of subjective measure and electromyography (EMG) responses. It also showed that increasing the carried weight more than 10% result in reducing activity on the erector spinal muscles, while it increases on abdominal oblique muscles. The developed backpack design confirmed the efficiency of its bases by distributing the carried weight among the trunk through side pockets, attached to the body through two upper and lower straps. It helped the body to distribute the carried weight and avoid concentrating pressure on specific areas.

A kinematic comparison of gait with a backpack versus a trolley for load carriage in children

The use of a school trolley is reaching and even surpassing the use of backpacks in many countries, although a recommended load has not been studied. To accomplish this, 3D gait kinematics of the lower limbs and thorax were analysed in 49 students walking unloaded, pulling a school trolley or carrying a backpack, all with either 10%, 15%, or 20% BW. The variables obtained were the degrees of flexion/extension, adduction/abduction and internal/external rotation of the thorax, pelvis, hip, knee and ankle. Statistical parametric mapping was used to evaluate differences between conditions and loads throughout the gait cycle. In the backpack conditions, the magnitudes of the differences decreased from proximal to distal joints compared to the unloaded condition. The use of a school trolley only required minor kinematic adaptations. Therefore, from kinematic analysis, it is recommended to avoid loads above 10% BW for children using a backpack and below 20% BW for children using a trolley.

Gait asymmetry and rating of perceived exertion: How are they influenced by carrying a backpack and pulling a trolley?

BACKGROUND

Carrying a backpack and pulling a school trolley have been previously related to changes in spatiotemporal gait parameters.

OBJECTIVE

Analyze gait asymmetry and rating of perceived exertion carrying a backpack and pulling a trolley with different loads.

METHODS

Fifteen students from an elementary school (aged 10.1 ± 1.7 years) participated in this study. The participants walked with no bag, and carrying a backpack or pulling a trolley, both with 10%, 15% and 20% of the participant's body weight (BW). A 3D motion capture system was used to analyze the spatiotemporal gait variables. Then, the ratios, symmetry angles and gait asymmetry of the step length, swing time, and stance time were analyzed. Furthermore, the rating of perceived exertion was recorded.

RESULTS

None of the asymmetry parameters were significantly different between those who carried a backpack and those who pulled a trolley. In the backpack condition, the ratings of perceived exertion were higher among participants in the 20% BW (2.07 ± 2.09, p = 0.003) and 10% BW (0.27 ± 0.59, p = 0.004) conditions compared to those in the control condition (0.07 + 0.26). Pulling a trolley did not significantly increase the perceived exertion ratings.

CONCLUSIONS

Carrying a backpack and pulling a trolley from 10% - 20% BW did not induce gait asymmetry in children. The use of the school trolley required less subjective effort than carrying a backpack with the same loads.

Variation of spatiotemporal parameters in school children carrying different backpack loads: a cross sectional study

The purpose of this study was to analyze spatiotemporal parameters of gait in children using varyingly loaded Backpacks(BP). This cross-sectional study examined 231 schoolchildren (118 boys, 113 girls) aged six to 12 years, carrying a traditional BP to manipulate loading (Crossing Backpack Children Arpenaz 7 Litres, Junior Red Quechua). Load was added to the BPs in increments of 5%, 10%, 15% and 20% of the child's body weight. Spatio-temporal parameters were measured with the OptoGait system. Significant differences were observed in single support (p < 0.001), and double support (p < 0.001). No statistically significant differences were observed in step length (p = 0.959) between the five loading conditions. Similarly, no statistically significant differences were found in the contact phase (p = 0.208), although significant changes were seen between baseline, 15% of body weight (p < 0.005), and 20% of body weight (p < 0.005). The effect sizes from the ANOVA in the single support was low (0.015), and double support was moderate (0.02). Increased weight in BPs reduced both children's balance and single support, increased double support, but did not change step length. The children increase double support with heavier loads to help their balance. The spatio-temporal changes were most evident with BP loads between 15-20% of body weight. Affective responses, including the perception of heaviness or difficulty in carrying the schoolbags need to be included in further and prospective investigations.

Pulling a school trolley: A good kinematic option for children

This study analyzed the kinematic gait parameters associated with pulling a school trolley with different loads and the effects of the type of packing device user (backpack vs. trolley) and body side (loadedunloaded). Methods Fifty-three elementary subjects walked at a selfselected speed under four experimental conditions: without a trolley and pulling a trolley with 10%, 15% and 20% of the subject́s body weight (BW). Averages and standard deviations of spatiotemporal gait parameters and 3D kinematics of the lower limbs and thorax were obtained for the loaded and unloaded sides of the body. Results Spatiotemporal gait parameters were affected by pulling a trolley with a load of 20% BW, although the changes were not important (decrease of 0.02 units in velocity and stride length, decrease of 0.32% in single support and increase of 0.31% in double support). In the 3D kinematics analysis, the main effects of trolley load were observed in the thorax, with increased flexion as the load increased, and in the pelvis between baseline and 10%-15% BW. No interaction was found between kinematic parameters and the type of packing device user (trolley or backpack). Considering the loaded and unloaded sides of the body, the transverse plane of the thorax was the main site affected by the asymmetrical task. Conclusion Although some of the analyzed kinematic parameters were influenced by the use of a school trolley, the adaptations were minimal, and trolleys could be considered a good option for use in the transportation of school supplies.