Heat stress increases carbohydrate oxidation rates and oxygen uptake during prolonged load carriage exercise.

Military missions are conducted in a multitude of environments including heat and may involve walking under load following severe exertion, the metabolic demands of which may have nutritional implications for fueling and recovery planning. Ten males equipped a military pack loaded to 30% of their body mass and walked in 20°C/40% relative humidity (RH) (TEMP) or 37°C/20% RH (HOT) either continuously (CW) for 90 min at the first ventilatory threshold or mixed walking (MW) with unloaded running intervals above the second ventilatory threshold between min 35 and 55 of the 90 min bout. Pulmonary gas, thermoregulatory, and cardiovascular variables were analyzed following running intervals. Final rectal temperature (MW: p < 0.001, g = 3.81, CW: p < 0.001, g = 4.04), oxygen uptake, cardiovascular strain, and energy expenditure were higher during HOT trials (p ≤ 0.05) regardless of exercise type. Both HOT trials elicited higher final carbohydrate oxidation (CHOox) than TEMP CW at min 90 (HOT MW: p < 0.001, g = 1.45, HOT CW: p = 0.009, g = 0.67) and HOT MW CHOox exceeded TEMP MW at min 80 and 90 (p = 0.049, g = 0.60 and p = 0.024, g = 0.73, respectively). There were no within-environment differences in substrate oxidation indicating that severe exertion work cycles did not produce a carryover effect during subsequent loaded walking. The rate of CHOox during 90 minutes of load carriage in the heat appears to be primarily affected by accumulated thermal load.

Differences in walking and running parameters in elementary school students with and without backpacks.

BACKGROUND: Backpack syndrome (BS) is a term used to describe symptoms such as shoulder and back pain that are believed to be caused by carrying a backpack. Few studies have investigated the changes in walking and running parameters with and without backpacks. OBJECTIVE: The present study aimed to investigate the differences in walking and running parameters with and without backpacks in primary school children with and without BS. METHODS: This cross-sectional study included 51 children (average age 9.3 years, 6- 12 years). Two questions were asked beforehand: whether the respondents had shoulder or back pain when going to school and present; those who answered that they had pain in both cases were defined as the BS group, while the others were the control group. Walking and running at comfortable speeds and walking and running with a 6 kg backpack on their backs were measured. RESULTS: During walking, there were main effects for speed, cadence, and strike angle with and without the backpack, but no interactions were identified for any of the parameters. In running, however, there were main effects for speed, stride length, strike angle, and lift-off angle, and an interaction effect was observed for speed and stride length. CONCLUSIONS: During walking, carrying a 6 kg backpack increased cadence and walking speed. During running, carrying a backpack caused a decrease in stride length and running speed in the BS group, whereas there was no change in the control group, suggesting that the control and BS groups may respond differently.

Examining the Backpack Weight Relative to Students' Body Weight Among Urban and Rural Schoolchildren: A Cross-Sectional Study.

Background Schoolbags or backpacks have been an essential part of the education system for a long time. However, a hefty backpack causes the child to arch the back excessively or bend their head and trunk forward to withstand the weight of the schoolbag. If the student carries the backpack on one shoulder, he/she bends to the opposite side to compensate for the extra weight, which may damage the shoulders and spine. Considering these factors, the main aim of this study was to investigate the percentage of backpack weight in proportion to the student's body weight regarding the new guidelines among urban and rural schoolchildren aged 12 to 15 years in Bangalore, Karnataka. Methodology In southern India, over a year, a cross-sectional study was conducted with 500 students who voluntarily participated after providing written consent. They completed a questionnaire, underwent vital and anthropometric measurements, and had their weights measured, including the weights of their backpacks. Sample bags were inspected to determine contributing weight factors and evaluate adherence to timetables. Results The average weight carried by children of all ages was 6.53 kg, averaging 13.53% of their body weight. Among males, the percentage carrying backpacks weighing over 10% of their body weight was 80.9%, while among females, it was 85.7%. Of all the males carrying bags weighing more than 10% of their body weight, 67.7% attended government schools, while 32.3% attended private schools. Among females studying in government schools, 63.6% carried backpacks weighing more than 10% of their body weight, while among those in private schools, 36.4% carried bags exceeding that weight. Conclusions The study concluded that despite regulations being implemented on backpack weight for children, a significant number still carry bags exceeding 10% of their body weight among both urban and rural school children. This could elevate pressure on neck and back muscles, leading to excessive fatigue and potential damage to the skeletal system, ultimately contributing to spinal deformities.

Comparison of muscle activity in school students while carrying backpacks and trolley bags.

BACKGROUND: Trolley bags have gained popularity among students, but there is limited research comparing them to backpack-style school bags. OBJECTIVE: This study aimed to compare how carrying a backpack versus a trolley bag affects the activity of trunk and lower limb muscles in secondary school students. METHODS: Electromyographic activity was measured in 25 students (13.4±1.1 years) as they walked on level ground and up/down stairs while carrying both types of bags. The activity of the gastrocnemius, tibialis anterior, semitendinosus, rectus femoris, lumbar erector spinae, and rectus abdominis muscles was assessed on both the dominant and non-dominant sides. RESULTS: The study found significantly reduced muscle activation in most of the targeted muscles when walking on level ground with the trolley bag and when going up/down stairs with the backpack. CONCLUSIONS: Lifting a trolley bag depends on the slope of the walking surface and is more efficient on level ground, while carrying a backpack is more efficient when going up and down stairs. Since it is not practical to switch bags when encountering stairs in schools, a bag with a mixed model design incorporating features of both trolley and backpack may be more beneficial and practical for students to use. Students, parents, and teachers should be aware of the injury risks associated with carrying different types of bags.

The impact of backpack load on adolescent's stair descent gait.

This study investigates the impact of increasing backpack load on the gait of adolescents during stair descent. Sixteen healthy male students (age = 12.9 ± 0.6 years) were required to descend the stairs in 4 loaded conditions. The kinematic, kinetic, and EMG data were collected synchronously and gait parameters, especially indicators of balance control, were analyzed. The posterior tilt angles (COM-COP IA in the sagittal plane) (0 %-42 %, 48 %-53 %, 58 %-91 %, p < 0.01), trunk anterior tilt angles (9-33 %, 51-65 %, p < 0.01), and CV of stride length (p < 0.01) increased with the backpack load. The COM-Step edge separation decreased with the increased backload (p < 0.01). In addition, the hip flexion torque (25-40 %, 45-51 %, p < 0.01), the rectus femoris activation, and the hip stiffness increased significantly as the load up to 15 % Body Weight (BW)and 20 % BW. The increasing backpack load may affect adolescent's stair descent gait. Especially as the load was up to 15 % BW, the adolescents' bodies tended to tilt backwards relative to the support foot during the single stance phase. They may activate the hip flexors and tilt forward the trunk to recover from the balance perturbation, which was associated with increased hip flexion torques. This adjustment was more pronounced with the increasing backpack load. However, excessive forward flexion may increase the risk of forward falls. The boundaries of adjustment need further research in the future. Findings from this study provide baseline information on the intrinsic mechanisms of balance control during stair descent.

Influence of Backpack Carriage and Walking Speed on Muscle Synergies in Healthy Children.

Four to five muscle synergies account for children's locomotion and appear to be consistent across alterations in speed and slopes. Backpack carriage induces alterations in gait kinematics in healthy children, raising questions regarding the clinical consequences related to orthopedic and neurological diseases and ergonomics. However, to support clinical decisions and characterize backpack carriage, muscle synergies can help with understanding the alterations induced in this condition at the motor control level. In this study, we investigated how children adjust the recruitment of motor patterns during locomotion, when greater muscular demands are required (backpack carriage). Twenty healthy male children underwent an instrumental gait analysis and muscle synergies extraction during three walking conditions: self-selected, fast and load conditions. In the fast condition, a reduction in the number of synergies (three to four) was needed for reconstructing the EMG signal with the same accuracy as in the other conditions (three to five). Synergies were grouped in only four clusters in the fast condition, while five clusters were needed for the self-selected condition. The right number of clusters was not clearly identified in the load condition. Speed and backpack carriage altered nearly every spatial-temporal parameter of gait, whereas kinematic alterations reflected mainly hip and pelvis adaptations. Although the synergistic patterns were consistent across conditions, indicating a similar motor pattern in different conditions, the fast condition required fewer synergies for reconstructing the EMG signal with the same level of accuracy.

Relationship between backpack load location, sex, anthropometric and body composition factors with postural sway in healthy young adults.

Objective: Evaluate the effect of backpack load location on postural sway and correlate sway path length (PL) to anthropometrics and body composition. Methods: Fifteen participants aged 18-25 stood on a force plate with backpack load located high (LH), low (LL) or without backpack (NL). Body composition and anthropometric variables were correlated to PL. Results: Load increased PL, 95% confidence ellipse, and mean velocity while it reduced mediolateral SampEn (p<0.05). Females had increased mean velocity and PL of sway (p<0.05). Larger phase angles correlated with reduced PL under NL. Taller individuals correlated with reduced PL under LL. Greater mass correlated with reduced PL under LH. Conclusions: Load carriage regardless of load location increased postural sway metrics except mediolateral SampEn. Females had greater PL and mean velocity compared to males. Select anthropometric and body composition variables correlated with postural sway under different load conditions.

Objectif: Évaluer l'effet de la position de la charge du sac à dos sur le balancement postural et corréler la longueur du chemin du balancement (PL) aux facteurs anthropométriques et à la composition corporelle. Méthodologie: Quinze participants âgés de 18 à 25 ans se sont tenus debout sur une plateforme biomécanique, la charge du sac à dos étant placée à un niveau élevé (LH), bas (LL) ou sans sac à dos (NL). La composition corporelle et les variables anthropométriques ont été corrélées à la PL. Résultats: La charge a augmenté la PL, l'ellipse de confiance à 95 % et la vitesse moyenne tout en réduisant la SampEn (entropie d'échantillon) médio-latérale (p<0,05). Les femmes avaient une vitesse moyenne et une PL de balancement plus élevées (p<0,05). Les angles de phase plus importants sont en corrélation avec une réduction de la PL sous NL. Les personnes plus grandes étaient en corrélation avec une réduction de la PL sous LL. Une masse plus importante est en corrélation avec une réduction de la PL sous LH. Conclusions: Le port de charge, quelle que soit la position de la charge, a augmenté les paramètres du balancement postural, à l'exception de la SampEn médio-latérale. Les femmes avaient une PL et une vitesse moyenne plus élevées que les hommes. Certaines variables anthropométriques et de composition corporelle sont en corrélation avec le balancement postural dans différentes conditions de charge.

Multi-joint protective effects of lumbar brace on lumbar, hip, knee, and ankle in parachute landing with backpack load.

There were high injury risks on lumbar and lower limb joints in parachuting landing, and the lumbar brace could protect lumbar. Besides, a backpack load was necessary in parachute landing and increased the injury risk. This study aimed to evaluate multi-joints protective effects of the lumbar brace on lumbar and lower limb joints in parachuting landing with the backpack load. Seven participants landed from a 120 cm height platform without and with a lumbar brace and without and with a 5-kg backpack load, respectively. Infrared makers were pasted on trunk, pelvis, and lower limb in order to build a multi-rigid-body model for calculating kinematic and kinetic parameters. The joint angular displacements of lumbar and ankle and the peak vertical ground reaction force were significantly decreased from 29.2 ± 9.2°, 45.2 ± 7.8°, and 14.7 ± 2.0 bodyweight to 21.6 ± 4.9° (p < 0.05), 39.0 ± 10.1° (p < 0.05) and 10.7 ± 1.3 bodyweight (p < 0.05) respectively by the lumbar brace with no backpack load, and the joint angular displacement of hip was significantly increased from 52.6 ± 7.2° to 68.3 ± 12.5° (p < 0.05). The joint angular displacement of lumbar and ankle were significantly decreased from 29.0 ± 5.0° and 53.8 ± 5.1° to 25.1 ± 5.2° (p < 0.05) and 48.5 ± 2.5° (p < 0.05) respectively by the lumbar brace with the backpack load, and the joint angular displacement of hip and knee were significantly increased from 60.1 ± 8.2° and 110.1 ± 9.3° to 69.7 ± 13.2° (p < 0.05) and 116.8 ± 5.8° (p < 0.05), respectively. The lumbar brace could provide the multi-joint protective effect by decreasing injuries of lumbar and ankle in landing both without and with the backpack load.

The Acute Effects of Schoolbag Loading on Posture and Gait Mechanics in 10- to 13-Year-Old Children: A Cohort from the North West Province.

Most schoolchildren carry schoolbags, of which a substantial proportion carry loads that exceed 15% of their body mass. Although the effects of loading have been investigated to varying degrees, the status of schoolbag loading and the acute affects thereof on gait and posture have not been thoroughly investigated within the South African context. A total of 60 participants in the 10-13-year age range volunteered for the present study. Significant differences were evident for relative load carriage (χ2(3) = 14.54, p < 0.001), forefoot and heel forces (Mdiff = 17.05-34.86 N, p < 0.001), force ratios (Mdiff = 0.02, p = 0.029), and gait speed (Mdiff = -0.18 km/hr, p = 0.016), but not for any postural angles (Mdiff = -3.37-6.08 deg, all p > 0.052). Those who exceeded 15% BM were ~9 times more likely to report pain than those below 15% BM. The children in the current study carried significantly heavier relative loads (p < 0.001) compared to similarly aged children from other countries. Loading leads to acute changes in posture and gait that are likely not meaningful. However, excessive loading (>15% BM) leads to significantly higher perceptions and reporting of pain in 10-13-year-old children.

Influences of dynamic load phase shifts on the energetics and biomechanics of humans.

Using load-suspended backpacks to reduce vertical peak dynamic load exerted on humans can reduce metabolic costs. However, is it possible to further reduce metabolic cost by modulating dynamic load phase shift? If so, is anti-phase better than the others? In this study, we investigated the biomechanics, energetics and trunk response under phase shifts. Nine subjects wearing an active backpack with 19.4 kg loads walked on a treadmill at 5 km h-1 with four phase shift trials (T1-T4) and a load-locked trial (LK). Our results show that anti-phase trial (T3) assists ankle more and reduces the moment and gastrocnemius medialis activity, while T4 assists knee more and reduces the moment and rectus femoris activity. Due to the load injecting more mechanical energy into human in T3 and T4, the positive centre-of-mass work is significantly reduced. However, the gross metabolic rate is lowest in T4 and 4.43% lower than in T2, which may be because the activations of erector spinae and gluteus maximus are reduced in T4. In addition, T3 increases trunk extensor effort, which may weaken the metabolic advantage. This study provides guidance for improving assistance strategies and human-load interfaces and deepens the understanding of the energetics and biomechanics of human loaded walking.

Air, Dermal, and Urinary Metabolite Levels of Backpack and Tractor Sprayers Using the Herbicide Acetochlor in Thailand.

Acetochlor is a chloroacetanilide selective pre-emergent herbicide used for controlling grass and broadleaf weeds in crops. This study compared the acetochlor exposures of backpack and tractor sprayers and assessed whether dermal or air exposures were more important contributors to the overall body burden as measured by urinary metabolites. Sixty sugarcane farmers in Nakhonsawan province, Thailand participated in the study, and breathing zone air and dermal patch samples were collected during spraying. Urine samples were collected before spraying, at the end of the spraying task, and on the day after spraying. For backpack and tractor sprayers, there was no significant difference in their breathing zone air concentrations, total body dermal samples, or urinary 2-methy-6-methyaniline (EMA) concentrations on the day after spraying. In addition, although most backpack and tractor sprayers wore long pants and long sleeve shirts, they were still exposed to acetochlor, as evidenced by a significant increase in the urinary EMA from before spraying (GM = 11.5 µg/g creatinine) to after spraying (GM = 88.5 µg/g creatinine) to the next day (GM = 111.0 µg/g creatinine). Breathing zone air samples were significantly correlated with those of total body dermal patch samples and with urinary EMA concentrations after spraying. This suggests that both air and dermal exposure contribute to urinary EMA levels.

Effect of harness design for tag attachment on the flight performance of five soaring species.

BACKGROUND: Bio-logging devices play a fundamental and indispensable role in movement ecology studies, particularly in the wild. However, researchers are aware of the influence that attaching devices can have on animals, particularly on their behaviour, energy expenditure and survival. The way a device is attached to an animal's body has also potential consequences for the collected data, and quantifying the type and magnitude of such potential effects is fundamental to enable researchers to combine and compare data from different studies, as much as it is to improve animal welfare. For over two decades, large terrestrial birds have been in the focus of long-term movement ecology research, employing bio-logging devices attached with different types of harnesses. However, comparative studies investigating the effects of different harness types used on these species are scarce. METHODS: In this study, we tested for potential differences in data collected by two commonly used harness types, backpack and leg-loop, on the flight performance of 10 individuals from five soaring raptor species, equipped with high resolution bio-logging devices, in the same area and time. We explored the effect of harness type on vertical speed, airspeed, glide ratio, height above sea level, distance travelled, proportion of soaring and flapping behaviour, and VeDBA (a proxy for energy expenditure) between and within individuals, all used as fine-scale measures of flight performance. RESULTS: Birds equipped with leg-loops climbed up to 0.36 ms[Formula: see text] faster, reached 25.9% greater altitudes while soaring and spent less time in active flight compared to birds equipped with backpacks, suggesting that backpack harnesses, compared to leg-loops, might cause additional drag affecting the birds' flight performance. A lower VeDBA, a lower rate of sinking while gliding and slightly higher glide ratio and airspeeds were also indicative of less drag using leg-loops, even though the effect on these parameters was comparable to inter-individual differences. CONCLUSIONS: Our results add to the existing literature highlighting the design-related advantages of leg-loops, and support the use of leg-loops as a better alternative to backpack harnesses for large soaring birds, when possible. Our study also highlights how apparently small changes in device attachment can lead to notable improvements in tagging practice, with implications for animal welfare, data interpretation and comparability.

Laboratory evaluation of occupational exposure to hand-arm vibration (HAV) during grounds maintenance equipment operations.

INTRODUCTION AND OBJECTIVE: About 2.5 million workers in the USA are exposed to hand-arm vibration (HAV) from power tools. The aims of the study were to evaluate occupational exposure to HAV during grounds maintenance equipment operations and the effect of general work gloves on vibration magnitude under controlled laboratory conditions. MATERIAL AND METHODS: A simulation of grass trimmer, backpack blower, and chainsaw operations was conducted by two participants to measure vibration total value (ahv) using vibration dosimeters wearing gloves. ahv was also measured on the bare hands during grass trimmer and backpack blower operations. RESULTS: ahv of the gloved hand was 3.5-5.8, 1.1-2.0, and 3.0-3.6 m/s2 during the grass trimmer, backpack blower, and chainsaw operations, respectively. ahv of the bare hand was 4.5-7.2 and 1.2-2.3 m/s2 for the grass trimmer and blower operations, respectively. CONCLUSIONS: The highest HAV exposure was observed during the grass trimmer operation which showed higher vibration attenuation of the gloves.

Comparison of the efficacy of different methods to apply acaricides for control of Rhipicephalus (Boophilus) microplus.

The present study compared the efficacy of different methods to apply an acaricide formulation to control Rhipicephalus (Boophilus) microplus. To compare the methods, an acaricide blend containing three active ingredients (a pyrethroid and two organophosphates) was used. In experiment 1 (farm 1: Goiânia, GO, Brazil), three methods were tested: a backpack sprayer (BS), power sprayer (PS) and spray race (SR). In experiment 2 (farm 2: São José do Rio Pardo, SP, Brazil), two methods were tested: BS and PS. In both experiments, 10 cattle with similar tick burdens were used. On day 0 in both experiments, the animals were treated with the acaricide. On day +1 (only in experiment 1), +3, +7, +14, +21, +28 and +35 (only in experiment 2), tick counts were performed to determine the control efficacy. The time application, pressure (KPa), volume applied (L) and ergonomic aspects of each spraying system were also evaluated. The adult immersion test (AIT) using three different acaricide blends (combinations of pyrethroid + organophosphate) was performed to compare the susceptibility of strains of each farm. In experiment 1, all treatments significantly reduced (p < 0.05) the number of ticks on the animals, and PS resulted in the greatest acaricide efficacy since day +1. In experiment 2, both treatments (PS and BS) reduced (p < 0.05) the tick burden, and as observed in experiment 1, PS resulted in the best reduction. The application times were 4.5, 150 and 330 s, while pressures were 306.8, 4,826.3 and 220.6 KPa for SR, PS and BS, respectively. In the AIT, the efficacy values were between 99.8 and 100% for the tick strain form farm 1 (Goiânia), while for tick strain from farm 2 (São José do Rio Pardo), the efficacy was between 67.2 and 80.9%. We conclude that the sprayer methods chosen influences the efficacy of the acaricide. All sprayer methods were efficient for acaricide application; the best efficacy was obtained using the PS, while the SR resulted in good efficacy and lower application time. The strain from farm 2 was less susceptible to all acaricides tested.

Field-measured canopy height may not be as accurate and heritable as believed: evidence from advanced 3D sensing.

Canopy height (CH) is an important trait for crop breeding and production. The rapid development of 3D sensing technologies shed new light on high-throughput height measurement. However, a systematic comparison of the accuracy and heritability of different 3D sensing technologies is seriously lacking. Moreover, it is questionable whether the field-measured height is as reliable as believed. This study uncovered these issues by comparing traditional height measurement with four advanced 3D sensing technologies, including terrestrial laser scanning (TLS), backpack laser scanning (BLS), gantry laser scanning (GLS), and digital aerial photogrammetry (DAP). A total of 1920 plots covering 120 varieties were selected for comparison. Cross-comparisons of different data sources were performed to evaluate their performances in CH estimation concerning different CH, leaf area index (LAI), and growth stage (GS) groups. Results showed that 1) All 3D sensing data sources had high correlations with field measurement (r > 0.82), while the correlations between different 3D sensing data sources were even better (r > 0.87). 2) The prediction accuracy between different data sources decreased in subgroups of CH, LAI, and GS. 3) Canopy height showed high heritability from all datasets, and 3D sensing datasets had even higher heritability (H2 = 0.79-0.89) than FM (field measurement) (H2 = 0.77). Finally, outliers of different datasets are analyzed. The results provide novel insights into different methods for canopy height measurement that may ensure the high-quality application of this important trait.

The Soft Prefabricated Orthopedic Insole Decreases Plantar Pressure during Uphill Walking with Heavy Load Carriage.

This study aimed to investigate the effect of varying the hardness of prefabricated orthopedic insoles on plantar pressure and muscle fatigue during uphill walking with a heavy backpack. Fifteen healthy male recreational athletes (age: 20.4 ± 1.0 years, height: 176.9 ± 5.7 cm, weight: 76.5 ± 9.0 kg) wore prefabricated orthopedic insoles with foot arch support; a heel cup with medium (MI), hard (HI), and soft (SI) relative hardnesses; and flat insoles (FI). They performed treadmill walking on uphill gradients with 25 kg backpacks. The plantar pressure and surface electromyographic activity were recorded separately, in 30 s and 6 min uphill treadmill walking trials, respectively. The HI, MI, and SI significantly decreased peak plantar pressure in the lateral heel compared to FI. The MI and SI significantly decreased the peak plantar pressure in the fifth metatarsal compared to FI. The MI significantly reduced the pressure-time integral in the lateral heel compared to FI. The HI significantly increased the peak plantar pressure and pressure-time integral in the toes compared to other insoles, and decreased the contact area in the metatarsal compared to SI. In conclusion, a prefabricated orthopedic insole made of soft material at the fore- and rearfoot, with midfoot arch support and a heel cup, may augment the advantages of plantar pressure distribution during uphill weighted walking.

Effects of Load Carriage on Postural Control and Spatiotemporal Gait Parameters during Level and Uphill Walking.

Load carriage and uphill walking are conditions that either individually or in combination can compromise postural control and gait eliciting several musculoskeletal low back and lower limb injuries. The objectives of this study were to investigate postural control responses and spatiotemporal parameters of gait during level and uphill unloaded (UL), back-loaded (BL), and front-loaded (FL) walking. Postural control was assessed in 30 asymptomatic individuals by simultaneously recording (i) EMG activity of neck, thoracic and lumbar erector spinae, and rectus abdominis, (ii) projected 95% ellipse area as well as the anteroposterior and mediolateral trunk displacement, and (iii) spatiotemporal gait parameters (stride/step length and cadence). Measurements were performed during level (0%) and uphill (5, 10, and 15%) walking at a speed of 5 km h-1 without and with a suspended front pack or a backpack weighing 15% of each participant's body weight. The results of our study showed that postural control, as indicated by increased erector spinae EMG activity and changes in spatiotemporal parameters of gait that manifested with decreased stride/step length and increased cadence, is compromised particularly during level and uphill FL walking as opposed to BL or UL walking, potentially increasing the risk of musculoskeletal and fall-related injuries.

The effect of backpack weight on the performance of basic short-term/working memory tasks while walking along a pre-determined route.

This study investigated possible backpack weight effects on the performance of three basic short-term/working memory (STM/WM) tasks conducted concurrently with the physical task of route walking. The STM/WM tasks were the Corsi block-tapping, digit span, and 3-back tasks, and, were employed to examine the visuo-spatial sketchpad, phonological loop and central executive components of the WM system. Four backpack weight levels (0%, 15%, 25% and 40% of body mass) were considered. Thirty participants conducted the three experimental tasks requiring physical-cognitive multitasking. Data analyses revealed that: (1) increased backpack weight resulted in decreases in the performance of the Corsi block-tapping and the 3-back task, but (2) backpack weight did not significantly affect the digit span task performance. The study results suggest that reducing backpack weight could benefit the performance of various cognitive tasks during route walking. The study findings may be useful for the ergonomics design of body-worn equipment and human-system interfaces.Practitioner summary: This study examined the backpack weight effects on the performance of three basic short-term/working memory tasks conducted concurrently with the physical task of route walking. The study revealed that reducing backpack weight could benefit various cognitive tasks during physical-cognitive multitasking, especially cognitive tasks that require visuospatial processing and executive control.

Usability and effects on gait of an optimized schoolchildren backpack.

BACKGROUND: Backpacks used by children is a global concern, because may cause musculoskeletal discomforts and pain. OBJECTIVE: The purpose of this study was to test the usability and effects on gait kinematics wearing the Trunkpack versus a traditional backpack and no backpack. METHODS: Twenty-four children (9 to 11 years old) from a public school participated in this study. The usability was evaluated after a five-week testing period using a questionnaire. Gait kinematics was evaluated (Vicon) when the children were wearing a standard backpack, an optimized backpack (Trunkpack), and no backpack. Both backpacks were loaded with 10% of body weight. RESULTS: Was observed more trunk, hip and knee flexion when the children carried a standard backpack in comparison using the Trunkpack and not carrying a backpack (p < 0.01). The Trunkpack and no backpack were similar. The Trunkpack was well accepted by the schoolchildren (81% positive responses), 79% liked the head opening, 88% liked the waist straps, and 83% liked the facility to put and take objects in and out of the Trunkpack. CONCLUSION: Trunkpack requires less postural adjustments during gait than a standard backpack. Gait kinematics with the Trunkpack was comparable to the gait without carrying a backpack.

Effects of Backpack Types on Kinematics and Plantar Pressure in College Students During Stairs Walking / 医用生物力学

Objective To analyze the influence of different backpack types and loads on kinematics and plantar pressure of college students during stair climbing, so as to provide references for choosing the appropriate backpack and carrying mode. Methods The Nokov infrared light point motion capture system and Podome plantar pressure system were used to analyze the differences in the range of motion ( ROM) of the trunk and lower limb joints, the kinematic parameters at the peak time, the peak pressure of each plantar partition, the contact time, the maximum pressure of the whole foot, the average pressure and the maximum contact area for 15 male college students during the support period of stair climbing. Results The 5% BW and 10% BW backpack loads reduced ROM of trunk rotation, increased ROM of ankle flexion/ extension and varus / valgus. The 10% BW backpack loads increased the peak pressure of the 1st and 3rd metatarsals bones and the maximum pressure of the whole foot ( P < 0. 05). Single-shoulder bag and handbag reduced ROM of trunk tilting and rotation, and increased ROM of ankle flexion and extension, hip flexion angle, peak pressure of foot arch and medial heel (P<0. 05). The double-shoulder bag loads increased peak pressure in the toe area (P<0. 05). Conclusions During walking on the stairs, the 5% BW and 10% BW backpack loads limited trunk rotation and increased ankle ROM. The 10% BW loads also increased the load in metatarsal area. The unilateral weight-bearing mode would make the trunk tilt to the unload side and rotate to the weight-bearing side. The pressure in toe area was higher when carrying double-shoulder bag, while single-shoulder bag and handbag mainly increased the pressure of arch foot and medial heel. It is suggested that college students choose symmetrical backpack scheme, and wisely allocate back weight to avoid the injury of foot area.