Load Carriage Research Articles

The metabolic demand of external load carriage in golfers: a comparison of a single versus double-strap golf bag

A golf bag filled with a set of clubs provides a substantial load. When carried over distance this can increase the demands placed upon the golfer, leading to discomfort, fatigue and injuries. This study aimed to compare the metabolic demands of 2 methods of golf bag carriage. A total of 16 healthy male recreational golfers participated in the study. Participants were given an initial familiarization session in which their self-selected walking speed was determined. This was utilized as the treadmill speed for all subsequent trials. The testing protocol consisted of 3 randomized trials of treadmill walking for 5 minutes in each of three conditions: unloaded, single-strap bag and double-strap bag. Equipment consisted of a double-strap golf bag with a standard set of clubs weighing 12.5kg. For all trials oxygen consumption (L·min-1), VO2 (mL·kg·min-1) respiratory minute volume (VE) (L·min-1), and heart rate (HR) were measured. Results showed that the double-strap bag required significantly less oxygen consumption (1.19±0.19 vs. 1.31±0.16 L·min-1, P<0.01) relative oxygen consumption (14.49±2.06 vs. 15.93±2.25 mL·kg·min-1, P<0.01), reduced respiratory minute volume (29.95±4.19 vs. 32.47±4.26 L·min-1, P<0.05), and lower heart rates (100.14±11.05 vs. 106.96±9.33 BPM, P<0.001) than the single-strap bag. Both methods of carriage showed significantly greater metabolic demands than the unloaded condition (P<0.05). The decreased metabolic cost of carrying a double-strap golf bag may facilitate a reduction in fatigue and reduced mechanical stress. Golf bag transportation must therefore be recognized as a factor in reducing the risk of injury and improving playing performance.

Energy performance analysis of a suspended backpack with an optimally controlled variable damper for human load carriage

This paper investigates the energy performance of human load carriage with a variable damped suspended backpack. A vertical double-mass coupled-oscillator model is adopted to predict the load movement and energy consumption. Optimal control is found to be bang-bang, switching four times between the minimum and the maximum damping in a step cycle. With analytically tested laws for optimal switching timing, an orbitally stable event-based control strategy with feedback is designed. Simulation results reveal that the suspended backpack with an optimally controlled variable damper improves the energy efficiency of load carriage and reduces the load force exerting on carriers for a wide range of suspension stiffness and walking conditions, representing less energy expenditure, better comfort and stronger adaptability over the passive elastic backpacks with constant suspension parameters. The working principle of the variable damper is also analyzed. Although this paper only deals with the theoretical model and analysis of the problem, the discussion on validity implies a considerable improvement in energy performance, including efficiency and adaptability.

Carbohydrate intake and ketosis in self-sufficient multi-stage ultramarathon runners

ABSTRACTUltra-endurance athletes accumulate an energy deficit throughout their events and those competing in self-sufficient multi-stage races are particularly vulnerable due to load carriage considerations. Whilst urinary ketones have previously been noted in ultra-endurance exercise and attributed to insufficient carbohydrate (CHO) availability, not all studies have reported concomitant CHO intake. Our aim was to determine changes in blood glucose and β-hydroxybutyrate concentrations over five days (240 km) of a self-sufficient multi-stage ultramarathon in combination with quantification of energy and macronutrient intakes, estimated energy expenditure and evaluation of energy balance. Thirteen runners (8 male, 5 female, mean age 40 ± 8 years) participated in the study. Glucose and β-hydroxybutyrate were measured every day immediately post-running, and food diaries completed daily. CHO intakes of 301 ± 106 g·day−1 (4.3 ± 1.8 g·kg−1·day−1) were not sufficient to avoid ketosis (5-day mean β-hydroxybutyrate: 1.1 ± 0.6 mmol.L−1). Furthermore, ketosis was not attenuated even when CHO intake was high (9 g·kg−1·day−1). This suggests that competing in a state of ketosis may be inevitable during multi-stage events where load reduction is prioritised over energy provisions. Attenuating negative impacts associated with such a metabolic shift in athletes unaccustomed to CHO and energy restriction requires further exploration.

Design of a load carriage system oriented to reduce acceleration forces when carrying a backpack

In military life, load carriage is an unavoidable part of field operations which is the reason why soldiers often make use of a military backpack. Infantry soldiers usually carry loads weighting more than 30% of their body weight. When the soldier carries a certain weight, his energy expenditure increases, which causes a reduction in performance. The transported load has a movement similar to the vertical displacement of the center of mass of the soldier while walking. This leads to a significant increase in the acceleration forces generated by the action of said load on the body which explains the increase in energy expenditure. The objective of this project was to develop a load carriage system that suspends the load and reduces its vertical displacement. Results show a reduction in both the vertical excursion of the load and in the total vertical ground reaction force when carrying a load with the developed prototype, with respect to the conventional military backpack.

Long-lasting chronic high load carriage of Epstein-Barr virus is more common in young pediatric renal transplant recipients

BackgroundEpstein-Barr virus (EBV) infections can induce post-transplant lymphoproliferative disorder (PTLD). A chronic high load (CHL), as indicated by long-term high EBV DNA levels after transplantation, has been associated with an enhanced risk of PTLD. We aimed to evaluate incidence, time of occurrence, risk factors, and outcome of EBV CHL carrier state after pediatric renal transplantation.MethodsA retrospective study of 58 children aged 1–17 years (median 10), who underwent renal transplantation between January 2004 and June 2017 at a single medical center. EBV IgG antibodies in serum were analyzed before and yearly after transplantation. EBV DNA in whole blood were analyzed weekly for the first 3 months post-transplant, monthly up to 1 year and then at least once yearly. CHL was defined as EBV DNA ≥ 4.2 log10 Geq/ml in > 50% of the samples during ≥ 6 months.ResultsAt transplantation, 31 (53%) patients lacked EBV IgG and 25 (81%) of them developed primary EBV infection post-transplant. Of the 27 seropositive patients, 20 (74%) experienced reactivation of EBV. Altogether, 14 (24%) children developed CHL, starting at a median of 69 days post-transplant and lasting for a median time of 2.3 years (range 0.5–6.5), despite reduction of immunosuppression. Patients with CHL were younger and 11/14 were EBV seronegative at transplantation. No child developed PTLD during median clinical follow-up of 7.8 years (range 0.7–13).ConclusionsCHL was frequent, long lasting, and occurred mainly in young transplant recipients. The absence of PTLD suggests that monitoring of EBV DNA to guide immunosuppression was effective.

Aerobic fitness, upper-body strength and agility predict performance on an occupational physical ability test among police officers while wearing personal protective equipment

Police institutions often use Occupational Physical Ability Tests (OPATs) as a measure of occupational performance. These tests are utilized to mimic the daily and essential tasks performed by the police officers, but few are performed with load carriage (LC). The purpose of this study was to examine the physical performance predictors of an OPAT performed without (NPPE) and with (WPPE) LC. Thirteen federal highway police officers (age: 36.8±3.7 years, body mass: 89±10.7 kg, height: 180±5.6 cm) volunteered to complete a battery of physical fitness tests (aerobic power and capacity, muscular endurance, lower limb power, upper limb strength, agility and anaerobic power) and anthropometrics. Occupational performance was measured by the total OPAT time consisting of 7 sequential police tasks. All subjects randomly completed the tests on both LC conditions. Agility (P<0.01), lower limb power and height (P<0.05) were significantly related to performance in the NPPE OPAT. In the WPPE condition, aerobic power (absolute and relative) (P<0.01), lower limb power and agility (P<0.05). The best predictors for OPAT performance were agility (R2=0.45, P<0.01) in the NPPE condition, as well as relative aerobic power, upper limb strength and agility in the WPPE condition (R2=0.81, P<0.01). Different conditions of LC have distinct occupational performance predictors. Thus, considering LC, physical exercise programs aimed at improving police occupational performance should aim at improving agility, upper limb strength and aerobic fitness.

The Effect of Tactical Tasks and Gear on Muscle Activation of SWAT Officers.

Keeler, JM, Pohl, MB, Bergstrom, HC, Thomas, JM, and Abel, MG. The effect of tactical tasks and gear on muscle activation of SWAT officers. J Strength Cond Res 36(1): 238-244, 2022-Special Weapons and Tactics (SWAT) officers perform a variety of tactical operations while wearing tactical gear. Load carriage has been shown to alter muscle activation in the torso and is also associated with lower back pain, which is a prevalent musculoskeletal injury suffered by SWAT Officers. The purpose of this study was to quantify the effect of tactical gear on muscle activation of torso musculature while performing occupational tasks. Twenty male SWAT Officers (age: 34.7 ± 4.5 years; height: 1.79 ± 0.1 m; body mass: 91.5 ± 17.3 kg) performed 4 tasks (standing, rifle walk, sitting, and shield walk) with and without gear (mass of gear: 13.8 ± 1.9 kg). Mean electromyographic amplitude was evaluated bilaterally for the erector spinae, rectus abdominis, and external oblique muscles during the trials and expressed relative to maximal voluntary isometric contraction (MVIC). Addition of gear significantly increased erector spinae mean muscle activation during the rifle walk task (mean delta: +0.16%). However, no differences in muscle activation were identified for any other muscles between gear conditions (effect size ≤ 0.15). The shield walk produced the highest mean activation for each muscle during different tasks. The dynamic tasks yielded (0.24-4.18% MVIC) greater muscle activation levels than sitting and standing tasks. Despite minimal increases in muscle activation levels with the addition of gear, load carriage is known to increase the risk of acute and chronic injury. Collectively, these findings indicate that SWAT Officers should perform most skills without gear during tactical training to simulate task-specific movement patterns but reduce the risk of musculoskeletal injury.

Effect of a load distribution system on mobility and performance during simulated and field hiking while under load

This study was conducted to test a modular scalable vest–load distribution system (MSV-LDS) against the plate carrier system (PC) currently used by the United States Marine Corps. Ten Marines engaged in 1.6 km load carriage trials in seven experimental conditions in a laboratory study. Kinematic, kinetic, and spatiotemporal gait parameters, muscle activity (electromyography), heart rate, caloric expenditure, shooting reaction times, and subjective responses were recorded. There was lower mean trapezius recruitment for the PC compared with the MSV-LDS for all conditions, and muscle activity was similar to baseline for the MSV-LDS. Twenty-seven Marines carrying the highest load were evaluated in the field, which measured an increase in energy expenditure with MSV-LDS; however, back discomfort was reduced. The field evaluation showed significantly reduced estimated ground reaction force on flat-ground segments with the MSV-LDS, and the data suggest both systems were comparable with respect to mobility and energy cost. Practitioner summary: This study found that a novel load distribution system appears to redistribute load for improved comfort as well as reduce estimated ground reaction force when engaged in hiking activities. Further, hiking with a load distribution system enables more neutral walking posture. Implications of load differences in loads carried are examined. Abbreviations: AGRF: anterior-posterior ground reaction forces; CAREN: Computer Assisted Rehabilitation Environment; GRF: ground reaction forces; HR: heart rate; ML-GRF: mediolateral ground reaction forces; MOLLE: Modular Lightweight Load-carrying Equipment; MSV-LDS: modular scalable vest–load distribution system; NHRC: Naval Health Research Center; PC: plate carrier; PPE: personal protective equipment; RPE: rating of perceived exertion; SAPI: small arms protective insert; sEMG: surface electromyography; USMC: United States Marine Corps; VGRF: Ground reaction forces in the vertical.

The effects of ankle stiffness on mechanics and energetics of walking with added loads: a prosthetic emulator study

BackgroundThe human ankle joint has an influential role in the regulation of the mechanics and energetics of gait. The human ankle can modulate its joint ‘quasi-stiffness’ (ratio of plantarflexion moment to dorsiflexion displacement) in response to various locomotor tasks (e.g., load carriage). However, the direct effect of ankle stiffness on metabolic energy cost during various tasks is not fully understood. The purpose of this study was to determine how net metabolic energy cost was affected by ankle stiffness while walking under different force demands (i.e., with and without additional load).MethodsIndividuals simulated an amputation by using an immobilizer boot with a robotic ankle-foot prosthesis emulator. The prosthetic emulator was controlled to follow five ankle stiffness conditions, based on literature values of human ankle quasi-stiffness. Individuals walked with these five ankle stiffness settings, with and without carrying additional load of approximately 30% of body mass (i.e., ten total trials).ResultsWithin the range of stiffness we tested, the highest stiffness minimized metabolic cost for both load conditions, including a ~ 3% decrease in metabolic cost for an increase in stiffness of about 0.0480 Nm/deg/kg during normal (no load) walking. Furthermore, the highest stiffness produced the least amount of prosthetic ankle-foot positive work, with a difference of ~ 0.04 J/kg from the highest to lowest stiffness condition. Ipsilateral hip positive work did not significantly change across the no load condition but was minimized at the highest stiffness for the additional load conditions. For the additional load conditions, the hip work followed a similar trend as the metabolic cost, suggesting that reducing positive hip work can lower metabolic cost.ConclusionWhile ankle stiffness affected the metabolic cost for both load conditions, we found no significant interaction effect between stiffness and load. This may suggest that the importance of the human ankle’s ability to change stiffness during different load carrying tasks may not be driven to minimize metabolic cost. A prosthetic design that can modulate ankle stiffness when transitioning from one locomotor task to another could be valuable, but its importance likely involves factors beyond optimizing metabolic cost.

Load Carriage for Female Military Personnel

ABSTRACT This article reviews the physiological, biomechanical, and health impacts of load carriage on the female soldier and includes issues impacting on the female athlete and hence female soldier. Physiological factors (e.g., mass, strength, and aerobic endurance) and biomechanical factors (e.g., forward trunk lean and step length) have the potential to increase the energy cost of load carriage and injury risk. Optimal load carriage conditioning guidelines are presented while considering issues specific to the female soldier, including the female athlete triad and pelvic floor muscle dysfunction, which can likewise reduce performance and increase injury risk.

The Effect of Personal Protective Equipment on Firefighter Occupational Performance.

Lesniak, AY, Bergstrom, HC, Clasey, JL, Stromberg, AJ, and Abel, MG. The effect of personal protective equipment on firefighter occupational performance. J Strength Cond Res 34(8): 2165-2172, 2020-The purpose of this study was to evaluate the effects of load carriage (LC) and LC plus respirator use (LC + self-contained breathing apparatus [SCBA]) on firefighters' work capacity to enhance our understanding of occupational demands. Twenty-one male structural firefighter recruits (age: 28.6 ± 4.3 years; height: 178.6 ± 7.2 cm; body mass: 94.1 ± 15.4 kg; body fat: 22.9 ± 6.1%) participated. Occupational performance was assessed by time to complete a simulated fire ground test (SFGT). After 2 familiarization trials, recruits performed the following SFGT conditions in a randomized order: PT (physical training clothes), LC only, and LC + SCBA. To describe within-group differences between SFGT conditions, relative difference scores were calculated as follows: % difference = ([experimental trial outcome - PT trial outcome]/PT trial outcome) × 100. Statistical differences between conditions were assessed with repeated-measures analysis of variance. The level of significance was set p < 0.01. Time to complete the LC + SCBA trial (345.9 ± 43.7 seconds; p < 0.001) and LC-only trial (331.2 ± 39.3 seconds; p < 0.001) were significantly greater than the PT trial (241.0 ± 33.3 seconds). Post-SFGT rating of perceived exertion was higher in the LC + SCBA trial (6.7 ± 1.7) and LC trial (6.4 ± 1.5) compared with the PT trial (4.7 ± 1.8; p < 0.001). Heart rate and lactate measures were similar across conditions (p = 0.488; p = 0.287). Personal protective equipment (PPE) significantly decreases the work capacity and increases the perceived effort of occupational tasks. Thus, these findings describe the additional physical demands produced by PPE and indicate that performance of firefighting tasks in an unloaded condition does not reflect work capacity in a bona fide condition.

Biomechanical Modelling Of Head-Head Load Carriage And Neuromuscular Control Of The Neck During Level Walking

Head load carriage is a common phenomenon in some parts of the world. This is prevalent across sub-Saharan Africa where women and children are used as pedestrian load-transporters. It has also been observed that during gymnasium and a few sporting activities, experienced gymnasts carry loads or other gymnasts by placing them their heads. The neck plays a major role in supporting the head in balance while generating the controlled head movements that are essential for balance in the head load carriage. Hence in this study, a biomechanical model of the controlled human head-head load carriage system is developed. The biomechanics model of the head loading problem in this study is a type of constrained mechanical three-dimensional, matrix coefficients, multibody systems which arise in many applications like robotics, vehicle and machinery dynamics. This governing equation was solved using Differential Transform Method (DTM) and was validated with the fourth order Runge-Kutta numerical method (RK4). Good agreements are reached between the two solutions. The effects of head mass, head load, neck mass were investigated. Other effects such as upper and lower linkage lengths were investigated in the study. As the head load increases, there were increases in both axial and angular displacement of the head and the neck motion.

Ankle and knee moment and power adaptations are elicited through load carriage conditioning in males

Soldiers routinely conduct load carriage and physical training to meet occupational requirements. These tasks are physically arduous and are believed to be the primary cause of musculoskeletal injury. Physical training can help mitigate injury risk when specifically designed to address injury mechanisms and meet task demands. This study aimed to assess lower-limb biomechanics and neuromuscular adaptations during load carriage walking in response to a 10-week evidence-based physical training program. Thirteen male civilian participants donned 23 kg and completed 5 km of load carriage treadmill walking, at 5.5 km h−1 before and after a 10-week physical training program. Three-dimensional motion capture and force plate data were acquired in over-ground walking trials before and after treadmill walking. These data were inputs to a musculoskeletal model which estimated lower-limb joint kinematics and kinetics (i.e., moments and powers) using inverse kinematics and dynamics, respectively. A two-way analysis of variance revealed significant main effect of training for kinematic and kinetics parameters at the knee and ankle joints (p < 0.05). Post-Hoc comparisons demonstrated a significant decrease (4.2%) in total negative knee power between pre- and post-March 5 km measures after training (p < 0.05). Positive power contribution shifted distally after training, increasing at the post-march measure from 39.9% to 43.6% at the ankle joint (p < 0.05). These findings demonstrate that a periodised training program may reduce injury risk through favourable ankle and knee joint adaptations.

Inter-individual variability in load carriage economy and comparisons between different load conditions

Equivocal findings exist for the economy associated with load carried close to the body's centre of mass. Individual variation could explain some of the equivocal findings. This research aimed to examine the extent of individual variation in loaded walking economy.Eighteen females carried load on the back, head and split between the front and back. Individual variation in relative load carriage economy (ELI) was primarily assessed using standard deviation, coefficients of variation (CV) and intraclass correlation coefficients (ICC).There was large inter-individual variation in ELI values with highest mean CV's of 16%, 12% and 10% for head-, back- and combined front and back-loading. Mean ELI values were not significantly different between methods.The large amount of individual variation found here suggests future load carriage research should account for individual variation, particularly when considering sample size and when making inferences on the economy associated with different types of load carriage using group mean data.

Morphofunctional characteristics of working mules in mountain areas of the Colombian Central Andes

The application of morphofunctional measurements allows the selection of suitable animals to perform working activities and ensure that animal maximum capacities are not exceeded. Mules are commonly used by small farmers for agricultural work in mountain areas where the access is extremely difficult. We aimed to estimate the functionality indexes of working mules in mountain areas of the Colombian Central Andes. A total of 94 adult mules were evaluated for withers height, thoracic perimeter, body length, neck length, and body weight, which were used to determine the body index (BI), proportionality index (PI), and load carriage index (LCI). Descriptive statistics, analysis of correlations, and principal component analysis were performed. Males presented higher morphometric measurements than females. There was a negative correlation between BI with PI and LCI. The principal component analysis was able to merge characteristics in two components explaining 81.78% of the variance in the indexes. These results demonstrated that working mules in the studied area have morphometric characteristics that define them as mesolinear animals with a low frame and broad chest, and these characteristics can function as a guide to identify desirable conformation indices for working mules, determining values of adequate load, respecting animal welfare.

Associations between Specialist Tactical Response Police Unit Selection Success and Urban Rush, along with 2.4 km and 10 km Loaded Carriage Events.

Officers serving in specialist tactical response police teams are highly trained personnel who are required to carry heavy loads and perform explosive tasks. The aim of this study was to determine whether performance on a loaded explosive occupational task (urban rush) or distance-based load carriage tasks (2.4 km or 10 km) were indicative of officer success on a specialist selection course (SSC). Eighteen male police officers (mean age = 32.11 ± 5.04 years) participated in the SSC over five consecutive days. Data were categorized into Group 1 (successful applicants, n = 11) and Group 2 (unsuccessful applicants, n = 7). Independent sample t-tests were performed to determine differences between groups, along with point-biserial correlations to investigate associations between anthropometric and event performance data and course completion success. Alpha levels were set at p = 0.05 a priori. Height (p = 0.025), body weight (p = 0.007), and 2.4 km loaded performance (p = 0.013) were significantly different between groups, where being shorter (rpb(16) = −0.526, p < 0.05), lighter (rpb(16) = −0.615, p < 0.01), and faster (rpb(16) = −0.572, p < 0.05) were associated with course success. While a loaded 2.4 km event is associated with success, a ceiling effect for an explosive anaerobic task and a longer 10 km task may exist, whereby increases in performance are not associated with selection success.

Altered forefoot function following a military training activity

BackgroundInjury rates are high in populations that regularly undertake weight-bearing physical activity, particularly military populations. Military training activities, that often include load carriage, have been associated with lower limb injury occurrence, specifically stress fractures. Research questionRecent work identified plantar loading variables as risk factors for lower limb stress fractures in Royal Marines recruits that were assessed during barefoot running. This study aimed to quantify how those plantar loading variables changed in Royal Marines recruits following a prolonged military load carriage activity, to further understand potential mechanisms for lower limb stress fractures. MethodsBilateral, synchronised plantar pressure and lower limb kinematic data were recorded during barefoot running at 3.6 m s−1 (±5%) pre- and post- a 12.8-km training activity (∼150 min). The training activity was completed with an average speed typical of walking (1.4 m.s-1), and 35.5 kg of additional load was carried throughout. Data were collected from 32 male Royal Marines recruits who completed the training activity in week-21 of the 32-week training programme. Plantar pressure variables and ankle dorsiflexion were compared between pre- and post-activity. ResultsPost-activity there was reduced loading under the forefoot and increased loading under the rearfoot and midfoot. There was no change in dorsiflexion touchdown angle, but an increase in peak dorsiflexion and range of motion post-activity. SignificanceThe increased rearfoot loading, reduced forefoot loading and increased ankle dorsiflexion following a prolonged military load carriage activity suggest a reduced transfer of loading from the rearfoot to the forefoot during stance, which may have implications for the development of stress fractures, particularly of the metatarsals.

The Weight of Schoolbags and Musculoskeletal Pain in Children of Selected Schools in Thimphu, Bhutan: A Cross-sectional Study

Background: The carriage of loads on the back in children, &gt;10% of one’s body weight (BW), induces postural change and morbidity related to spinal pain. We studied the weight of schoolbags and the prevalence of musculoskeletal pain related to carrying schoolbags among children in Thimphu, Bhutan.&#x0D; Methods: This was a cross-sectional study, with a multistage cluster sampling, conducted amongst grade 8 and 10 students. Data were collected using a standardized self-administered questionnaire and weights of students and schoolbags were measured. Descriptive statistics were used to present the findings. Means were compared using t test and risk factors were identified using logistic regression.&#x0D; Results: There were 131 students whose schoolbags weighed &gt;10% body weight (BW). The mean weight of schoolbags was 4.6 ±1.5 kg for grade 8 students and 4.0 ±1.5 kg for grade 10 students. Musculoskeletal pain in at least one body region was reported by 411 students. Schoolbags weighing &gt;10% BW and carrying the bags over only one shoulder were significant risk factors for reporting musculoskeletal pain. There were 197 students whose schoolbags did not have any safety feature; students did not use them consistently even if they were present.&#x0D; Conclusions: The weight of school bags that were more than the recommended ≤10% BW was a strong factor in reporting musculoskeletal pain. Parents and students may be educated on the use of schoolbags with safety features. Measures such as providing storage facilities in schools may reduce the weight of bags.

Design, model, and performance evaluation of a biomechanical energy harvesting backpack

Abstract Introducing compliant elements to backpack structures has been shown to reduce both the peak forces experienced by the user and the metabolic cost of walking. In previous work, we developed a novel load carriage system that allowed weight carried in a backpack to oscillate in the medial-lateral direction. In this paper, we introduce a new energy harvesting module, to be added to the load carriage module, that generates electricity from the movement of the carried mass. The energy harvesting module is implemented for two outcomes: to generate electricity for powering portable electronics and to effectively modulate oscillation amplitude and phase of the carried mass in the load carriage system. This paper outlines the design, model, and performance evaluation of our novel energy harvesting device. First, a model was developed so that we may determine device parameters that result in desired device behaviour. Then, the model was evaluated using a combination of bench top experiments and human walking experiments to validate its predictive capabilities. Testing revealed that the model can be used to predict general device behaviour, but could be further developed to improve accuracy. Lastly, we evaluated device performance in human walking experiments. The energy harvesting device generated up to 0.22 ± 0.08 W of electrical power while walking. Walking with the device while generating electricity did not significantly increase user effort, compared to walking with the weight rigidly fixed.

Dynamic Analysis of the Biomechanical Model of Head Load Impact Using Differential Transform Method

The dynamic analysis of the biomechanical model of the head load impact using the Differential Transform Method is presented in this paper. In many parts of the world, the problem of traumatic brain injuries (TBI) has led to neurodegenerative dementing disorders and diseases as a result of head load impact from sporting activities, accidents involving the head, etc. have serious effects on humanity. The head load impact and its control have been modeled as a rigid linkage head-neck manipulator. This rigid link manipulator is governed by a system of nonlinear ordinary differential matrix equations with three degrees of freedom which requires special techniques for its solution. The system of equations was solved using Differential Transform Method (DTM) and the results were compared with results obtained in earlier studies and validated with the fourth-order Runge-Kutta numerical method (RK4). Good agreements are reached in all these results. From the model, the effects of head loads, head mass, neck mass, upper and lower linkage lengths, head and neck moments of inertia were investigated. As the head loads increased, there were increases in both axial and angular displacement of the head motion and the neck region. The study provides a theoretical basis for the design and understanding of the effects of head load carriage on vital organs that are susceptible to pains, damages, and even failure.