Load Carriage Research Articles

Biomechanical Consequences of Walking With the Suspended Backpacks.

This article aimed to investigate the biomechanical mechanisms underlying the energetic advantages of the suspended backpacks during load carriage. In this study, we examined eight adults walking with a 15 kg load at 5 km/h with a designed suspended backpack, in which the load could be switched to locked and suspended with four combinations of stiffness. Mechanical work and metabolic cost were measured during load carriage. The results showed that the suspended backpacks led to an average reduction of 23.35% in positive work, 24.77% in negative work, and a 12.51% decrease in metabolic cost across all suspended load conditions. Notably, the decreased mechanical work predominantly occurred during single support (averaging 84.19% and 71.16% for positive and negative work, respectively), rather than during double support. Walking with the suspended backpack induced a phase shift between body movement and load movement, altering the human-load interaction. This adjustment caused the body and load to move against each other, resulting in flatter trajectories of the human-load system center of mass (COM) velocities and corresponding profiles in ground reaction forces (GRFs), along with reduced vertical excursions of the trunk. Consequently, this interplay led to flatter trajectories in mechanical work rate and reduced mechanical work, ultimately contributing to the observed reduction in energetic expenditure. Understanding these mechanisms is essential for the development of more effective load-carrying devices and strategies in various applications, particularly for enhancing walking abilities during load carriage.

The Agreement between Wearable Sensors and Force Plates for the Analysis of Stride Time Variability.

The variability and regularity of stride time may help identify individuals at a greater risk of injury during military load carriage. Wearable sensors could provide a cost-effective, portable solution for recording these measures, but establishing their validity is necessary. This study aimed to determine the agreement of several measures of stride time variability across five wearable sensors (Opal APDM, Vicon Blue Trident, Axivity, Plantiga, Xsens DOT) and force plates during military load carriage. Nineteen Australian Army trainee soldiers (age: 24.8 ± 5.3 years, height: 1.77 ± 0.09 m, body mass: 79.5 ± 15.2 kg, service: 1.7 ± 1.7 years) completed three 12-min walking trials on an instrumented treadmill at 5.5 km/h, carrying 23 kg of an external load. Simultaneously, 512 stride time intervals were identified from treadmill-embedded force plates and each sensor where linear (standard deviation and coefficient of variation) and non-linear (detrended fluctuation analysis and sample entropy) measures were obtained. Sensor and force plate agreement was evaluated using Pearson's r and intraclass correlation coefficients. All sensors had at least moderate agreement (ICC > 0.5) and a strong positive correlation (r > 0.5). These results suggest wearable devices could be employed to quantify linear and non-linear measures of stride time variability during military load carriage.

A Simulation-Based Framework to Determine the Kinematic Compatibility of an Augmentative Exoskeleton during Walking

Augmentative exoskeletons (AEs) are wearable orthotic devices that, when coupled with a healthy individual, can significantly enhance endurance, speed, and strength. Exoskeletons are function-specific and individual-specific, with a multitude of possible configurations and joint mechanisms. This complexity presents a challenging scenario to quantitatively determine the optimal choice of the kinematic configuration of the exoskeleton for the intended activity. A comprehensive simulation-based framework for obtaining an optimal configuration of a passive augmentative exoskeleton for backpack load carriage during walking is the theme of this research paper. A musculoskeletal-based simulation approach on 16 possible kinematic configurations with different Degrees of Freedom (DoF) at the exoskeleton structure’s hip, knee, and ankle joints was performed, and a configuration with three DoF at the hip, one DoF at the knee, three DoF at the ankle was quantitatively chosen. The Root Mean Square of Deviations (RMSD) and Maximum Deviations (MaxDev) between the kinematically coupled human–exoskeleton system were used as criteria along with the Cumulative Weight Score (CWS). The chosen configuration from the simulation was designed, realised, and experimentally validated. The error of the joint angles between the simulation and experiments with the chosen configuration was less than 3° at the hip and ankle joints and less than 6° at the knee joints.

Altered movement dynamics in soldiers undergoing multiple bouts of load carriage

Altered movement dynamics in soldiers undergoing multiple bouts of load carriage

Effectiveness of a passive military exoskeleton in off-loading weight during static and dynamic load carriage: A randomised cross-over study

BackgroundLoad carriage imposes high physical stresses on the human body, increasing the risk of injuries. This study assessed the effectiveness of a passive military exoskeleton in off-loading the weight placed on the body during heavy load carriage under static standing and dynamic walking conditions. MethodsEight full-time regular personnel of the Singapore Armed Forces enrolled in the study. Static loading tests included nine trials of 10-s quiet standing while carrying different loads (0–55 kg) with and without the exoskeleton. For dynamic loading, participants walked on a treadmill on flat, inclined, and declined surfaces while carrying two different loads (25 kg, 35 kg) with and without the exoskeleton. In-shoe normal ground reaction forces (GRF) were recorded during quiet standing and treadmill walking. Differences in total force with and without the exoskeleton during static loading were compared using Wilcoxon one-sample signed ranked tests against zero (no weight off-load) as a reference. Statistical parametric mapping test was used to compare the walking in-shoe GRF-time series with and without exoskeleton use for each load and surface condition. ResultsExoskeleton use was effective in off-loading loads of 2.3–13.5 kg during static quiet standing but the response varied substantially across loads and among the participants. Statistical analysis revealed no meaningful differences in the walking in-shoe GRF with and without exoskeleton use. The results were largely consistent across flat, inclined, and declined surfaces, and both 25-kg and 35-kg loads. ConclusionsThe passive military exoskeleton was effective in off-loading some load from the human body during static quiet standing but not dynamic walking on flat and sloped surfaces. The varied response across loads and participants calls for better design and fitting of the military exoskeleton to individual users.

Exogenous erythropoietin increases hematological status, fat oxidation, and aerobic performance in males following prolonged strenuous training.

This study investigated the effects of EPO on hemoglobin (Hgb) and hematocrit (Hct), time trial (TT) performance, substrate oxidation, and skeletal muscle phenotype throughout 28 days of strenuous exercise. Eight males completed this longitudinal controlled exercise and feeding study using EPO (50 IU/kg body mass) 3×/week for 28 days. Hgb, Hct, and TT performance were assessed PRE and on Days 7, 14, 21, and 27 of EPO. Rested/fasted muscle obtained PRE and POST EPO were analyzed for gene expression, protein signaling, fiber type, and capillarization. Substrate oxidation and glucose turnover were assessed during 90-min of treadmill load carriage (LC; 30% body mass; 55 ± 5% V̇O2peak) exercise using indirect calorimetry, and 6-6-[2H2]-glucose PRE and POST. Hgb and Hct increased, and TT performance improved on Days 21 and 27 compared to PRE (p < 0.05). Energy expenditure, fat oxidation, and metabolic clearance rate during LC increased (p < 0.05) from PRE to POST. Myofiber type, protein markers of mitochondrial biogenesis, and capillarization were unchanged PRE to POST. Transcriptional regulation of mitochondrial activity and fat metabolism increased from PRE to POST (p < 0.05). These data indicate EPO administration during 28 days of strenuous exercise can enhance aerobic performance through improved oxygen carrying capacity, whole-body and skeletal muscle fat metabolism.

Cardiovascular Demand Differences Between Male and Female US Marine Recruits During Progressive Loaded Hikes.

Schram, B, Orr, R, Niederberger, B, Givens, A, Bernards, J, and Kelly, KR. Cardiovascular demand differences between male and female US Marine recruits during progressive loaded hikes. J Strength Cond Res 38(8): e454-e458, 2024-Despite having to carry the same occupational load, female soldiers tend to be lighter than male soldiers. The aim of this study was to determine the differences in cardiovascular load between female and male US Marine recruits during progressive load carriage hikes. United States Marine Corps recruits (565 male recruits; 364 female recruits) completed 6 loaded hikes over 6 weeks (1: 10 kg, 30 minutes; 2: 10 kg, 45 minutes; 3: 15 kg, 30 minutes, 4: 15 kg, 45 minutes; 5: 20 kg, 30 minutes; 6: 20 kg, 45 minutes) during which cardiovascular response was measured. Average heart rate (HRavg), HR maximum (HRmax), and pace were measured via a wrist-worn physiological monitor. Independent sample t -tests were conducted to compare between sexes, with significance set at 0.008 after adjusting for multiple comparisons. The average female recruit had significantly lower body mass (BM) compared with the average male recruit ( p < 0.001) and thus carried a significantly heavier relative load. (10 kg ∼17%, 15 kg ∼25%, 20 kg ∼33%, p < 0.001). There were no significant differences in pace in any hike, and no significant differences were found in HRavg or HRmax when comparing female and male Marines during Hike 1. For female Marines, HRavg was significantly higher compared with male Marines during Hike 2 (+6.5 b·min -1 , p < 0.001) and Hike 3 (+7.4 b·min -1 , p < 0.001), and both HRavg and HRmax were significantly higher in Hike 4 (+11.9 b·min -1 , +8.4 b·min -1 , p < 0.001), Hike 5 (+7.7 b·min -1 , +7.9 b·min -1 , p < 0.001), and Hike 6 (+6.9 b·min -1 , +7.1 b·min -1 , p < 0.001), respectively. Female Marines endured greater cardiovascular demand compared with male Marines during load carriage events when carrying loads greater than 15 kg (∼25% BM).

Load carriage changes tibiofemoral arthrokinematics during ambulatory tasks in recruit-aged women

The introduction of women into U.S. military ground close combat roles requires research into sex-specific effects of military training and operational activities. Knee osteoarthritis is prevalent among military service members; its progression has been linked to occupational tasks such as load carriage. Analyzing tibiofemoral arthrokinematics during load carriage is important to understand potentially injurious motion and osteoarthritis progression. The study purpose was to identify effects of load carriage on knee arthrokinematics during walking and running in recruit-aged women. Twelve healthy recruit-aged women walked and ran while unloaded (bodyweight [BW]) and carrying additional + 25%BW and + 45%BW. Using dynamic biplane radiography and subject-specific bone models, tibiofemoral arthrokinematics, subchondral joint space and center of closest contact location between subchondral bone surfaces were analyzed over 0–30% stance (separate one-way repeated measures analysis of variance, load by locomotion). While walking, medial compartment contact location was 5% (~ 1.6 mm) more medial for BW than + 45%BW at foot strike (p = 0.03). While running, medial compartment contact location was 4% (~ 1.3 mm) more lateral during BW than + 25%BW at 30% stance (p = 0.04). Internal rotation was greater at + 45%BW compared to + 25%BW (p < 0.01) at 30% stance. Carried load affects tibiofemoral arthrokinematics in recruit-aged women. Prolonged load carriage could increase the risk of degenerative joint injury in physically active women.

Army Combat Fitness Test Scores Moderate Cognitive Function Improvements After a Ruck March: A Hierarchical Linear Model Approach.

Sax van der Weyden, M, Merrigan, JJ, Newman, K, Hahn, J, and Martin, J. Army Combat Fitness Test scores moderate cognitive function improvements after a ruck march: A hierarchical linear model approach. J Strength Cond Res 38(7): 1314-1320, 2024-Heavy load carriage is a common task for military personnel and can lead to undue physical and mental fatigue. The purpose of this study was to assess effects of load carriage on cognitive function (CF) and the role individual characteristics play in CF responses. Anthropometrics/body composition, demographics, and Army Combat Fitness Test (ACFT) scores were gathered from 47 Reserve Officers' Training Corps cadets. Cadets' CF was assessed through the concentration task grid (CTG) before (preruck), immediately after (postruck), and 3 weeks after (follow-up) a 16.09- to 19.31-km ruck march. Hierarchical linear modeling was used, with α < 0.05. The final model revealed growth, or improvement, in CF from preruck to postruck with growth decelerating, but still improved, at follow-up. The load carriage bout improved CF in most cadets, with average growth from 5.67- to 7.20-grid squares found. However, postruck CF did not return to the same level as a controlled follow-up (9.69). Sex (2.46, female), familiarity with the CTG (1.99), ACFT total scores (0.009), and relative ruck mass (-0.09) were all significant predictors of postruck CF. Army Combat Fitness Test scores (0.008) were also significant predictors of the slope between preruck and postruck, such that an ACFT score 59 points above average would result in a 1-grid square greater improvement in CF postruck. The significance of ACFT scores, lower relative ruck mass, and familiarization highlights the importance physical and mental preparation for desirable CF outcomes after occupational tasks.

Load Carriage and Changes in Spatiotemporal and Kinetic Biomechanical Foot Parameters during Quiet Stance in a Large Sample of Police Recruits

Background: Little evidence has been provided regarding the effects of carrying standardized load equipment and foot parameters during quiet standing. Therefore, the main purpose of the study was to examine whether a load carriage might impact static foot parameters in police recruits. Methods: Eight hundred and forty-five police recruits (27.9% women) were tested in ‘no load’ vs. standardized ‘3.5 kg load’ conditions. Foot characteristics during standing were assessed with the Zebris FDM pedobarographic pressure platform. Results: Carrying a 3.5 kg load significantly increased the 95% confidence ellipse area (∆ = 15.0%, p = 0.009), the center of pressure path length (∆ = 3.3%, p = 0.023) and average velocity (∆ = 11.1%, p = 0.014), the length of the minor axis (∆ = 8.2%, p &lt; 0.009) and the deviation in the X (∆ = 12.4%, p = 0.005) and Y (∆ = 50.0%, p &lt; 0.001) axes. For relative ground reaction forces, a significant increase in the left forefoot (∆ = 2.0%, p = 0.002) and a decrease in the left hindfoot (∆ = −2.0%, p = 0.002) were shown. No significant changes in relative ground reaction forces beneath the forefoot and hindfoot regions for the right foot were observed (p &gt; 0.05). Conclusions: The findings suggest that spatial and temporal foot parameters may be more prone to change while carrying heavy loads, especially the center of pressure characteristics.

Profiling injuries sustained following implementation of a progressive load carriage program in United States marine corps recruit training.

Load carriage tasks during United States Marine Corps (USMC) recruit training can cause injury. Load carriage conditioning, if optimized, can reduce injury risk. To compare injuries sustained by USMC recruits following participation in either the Original Load Carriage (OLC) program or a Modified Load Carriage (MLC) program. Retrospective musculoskeletal injury data were drawn from the USMC San Diego Sports Medicine injury database for recruits completing the OLC (n = 2,363) and MLC (n = 681) programs. Data were expressed as descriptive statistics and a population estimate of the OLC:MLC relative risk ratio (RR) was calculated. The proportion of injuries sustained in the MLC cohort (n = 268; 39% : OLC cohort, n = 1,372 : 58%) was lower, as was the RR (0.68, 95% CI 0.61- 0.75). The leading nature of injury for both cohorts was sprains and strains (OLC n = 396, 29%; MLC n = 66; 25%). Stress reactions were proportionally higher in MLC (n = 17, 6%; OLC n = 4, 0.3%), while stress fractures were proportionately lower (MLC n = 9, 3%; OLC n = 114, 8%). Overuse injuries were lower in MLC (- 7%). The knee, lower leg, ankle, and foot were the top four bodily sites of injuries and the Small Unit Leadership Evaluation (SULE), Crucible, overuse-nonspecific, running, and conditioning hikes were within the top five most common events causing injury. The prevalence rates of moderate severity injury were similar (MLC = 23%; OLC = 24%), although MLC presented both a higher proportion and prevalence of severe injuries (MLC = 6%; OLC = 3%, respectively). A periodized load carriage program concurrently increased exposure to load carriage hikes while reducing injuries both during the load carriage hikes and overall.

Occupational biopsychosocial factors associated with neck pain intensity, neck-disability, and sick leave: A cross-sectional study of construction labourers in an African population.

The burden and impact of neck pain is high in African countries including Nigeria. This study investigated the occupational biomechanical and occupational psychosocial factors associated with neck pain intensity, neck disability and sick leave amongst construction labourers in an urban Nigerian population. This cross-sectional study measured clinical neck pain outcomes, occupational biomechanical factors, and occupational psychosocial factors. Descriptive, and univariate/multivariate inferential statistical analyses were conducted. Significant independent factors associated with neck pain intensity were order and pace of tasks being dependent on others (β = 0.35; p<0.0001); inability to take breaks in addition to scheduled breaks (β = 0.25; p<0.0001); inability to work because of unexpected events (β = 0.21; p<0.0001); inability to control the order and pace of tasks (β = 0.20; p<0.0001); and weight of load (β = 0.17; p<0.0001); accounting for 53% of the variance in neck pain intensity. Significant independent factors associated with neck disability were weight of load (β = 0.30; p<0.0001); duration of load carriage (β = 0.16; p = 0.01); working under time pressure/deadlines (β = 0.16; p = 0.02); and accounting for 20% of the variance in neck disability. Significant independent factor associated with sick leave was duration of load carriage (β = 0.15; p = 0.04), in a non-significant regression model explaining -4% of the variance in sick leave. Addition of pain intensity significantly explained more variance in neck disability (31.0%) but less variance in sick leave (-5%), which was not statistically significant (F (10, 190) = 0.902, p = 0.533). Occupational biomechanical factors may be more important than occupational psychosocial factors in explaining neck disability and sick leave. In contrast, occupational psychosocial factors may be more important than occupational biomechanical factors in explaining neck pain intensity in this population in Nigeria.

Estimating metabolic rate from ISO heart rate method and two walking equations.

Assigning a value for metabolic rate is central to heat stress assessment. ISO 8996 describes a predictive method for walking based on the American College of Sports Medicine (ACSM) method and another generalized method based on average heart rate. In addition, the US Army uses the load carriage decision aid (LCDA) predictive equation to estimate metabolic rate. The purpose of this study was to assess the accuracy/bias and precision of the ISO heart rate method and the ACSM and LCDA equations. The laboratory database included metabolic rate, heart rate, treadmill speed, and grade during a progressive heat stress protocol. Treadmill speed and grade were set to represent one of three metabolic rates. Accuracy and precision were assessed with Bland-Altman plots. All three methods had good accuracy (low bias). For precision, the ISO heart rate method had a root mean square error (RMSE) of 34 W and 11% when adjusted for repeated measures. The RMSE for two equations was 20 W and 7%. Although the heart method had less accuracy, its application is more generalizable. The heart rate method should be used below the occupational exposure limit for heat stress to avoid a bias toward higher predicted values due to heat strain.

Does Walking with a Load Affect Asymmetry in Bilateral Lower Extremity Mechanics?

PURPOSE This study sought to analyze the velocity and asymmetry between bilateral lower extremity mechanics according to the load during walking.METHODS A total of 14 adults with right leg dominance participated in this study (Male=7, Female=7). We respectively applied 30% of body weight load carriage on the subjects. Gait characteristics were analyzed with 3-dimensional cinematography and ground reaction force (GRF) system consisted of a center of gravity (COG) velocity, center of pressure (COP) area, leg stiffness, and GRF components.RESULTS Change in velocity of the maximum-minimum COG showed statistically significant in the main effect of load. The 1st anterior-posterior GRF (braking force) and vertical GRF were statistically significant in the main effects of load and bilateral lower limbs. The 2nd anterior-posterior GRF (propulsive force) was statistically significant in the main effect of load. COP area and leg stiffness exhibited statistically significant differences in the main effects of load and bilateral lower limbs. Interaction was observed in the vertical GRF, COP area. Furthermore , one-way variance analysis revealed load main effect had a greater influence on the increase in the magnitude of the vertical GRF and COP area than the asymmetry of bilateral lower limbs.CONCLUSIONS This study revealed the differences in asymmetry between the dominant and non-dominant lower limbs according to the load during walking. These findings may explain the differences shock attenuation and stress mechanisms between the bilateral lower limbs.

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

ABSTRACT 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.

Biomechanical responses on specific load carriage and positive gradient walking: A pilot study

Objectives: Normal load carriage is an inevitable part of military marching tasks. Military tasks are inextricably related to carrying huge loads irrespective of different terrain. Continuous carrying of heavy loads from level ground to uphill gradient may alter kinetic and kinematic responses. Such responses, in the long run, may cause the risk of injury. This study was designed to find out the effects of external load on kinetic and kinematic responses at specific loads and grades (+10°). Materials and Methods: Six healthy Indian soldiers mean (± standard error of mean [SEM]) age 30.5 ± 3.5 years, height 168.7 ± 2.8 cm, weight 73.8 ± 7.08 kg participated in this study, walking on treadmill (Deneb and Polak-speed-1625) at 3.5 kmph for 6 min at 10° inclination for two conditions, with no-load and 30 kg compact-load at controlled laboratory condition 25°C and 50% relative humidity (RH). Compressive, shearing, torque, joint reaction force, and erector-spine forces for kinetic and angular changes of neck, trunk, thigh, forearm, upper arm, and leg were analysed by biomechanical analysis software (Ergomaster 4.6). A paired t-test and repeated measures analysis of variance were applied to determine the significant effects of the load on dependent variables. Results: Significant changes were found in kinetic (compressive, shearing, torque, joint reactive force, and erector spine force) and kinematic (neck and trunk) parameters with subsequent increments of loads. Conclusion: From this study, it was concluded that walking in uphill condition, compressive, shearing, torque, joint reactive force, and erector spine force was found to be increased by 2.58, 4.65, 4.06, 2.83, and 4.06 folds, the angular changes found in neck and trunk were 1.78 and 1.25 folds compared to no-load conditions, respectively. The exerted forces, namely compressive force 74.12%, shearing force 86%, joint reaction force almost 75%, and erector spine force 83.82%, were very close to the injury risk profile; only the change of torque was not much closer to the risk profile. Such findings could be used for recommending load carriage guidelines for future studies.

The test–retest reliability of physiological and perceptual responses during treadmill load carriage

PurposeUnderstanding the test–retest reliability of physiological responses to load carriage influences the interpretation of those results. The aim of this study was to determine the test–retest reliability of physiological measures during loaded treadmill walking at 5.5 km h−1 using the MetaMax 3B.MethodsFifteen Australian Army soldiers (9 male, 6 female) repeated two 12-min bouts of treadmill walking at 5.5 km h−1 in both a 7.2 kg Control condition (MetaMax 3B, replica rifle) and a 23.2 kg Patrol condition (Control condition plus vest) across three sessions, separated by one week. Expired respiratory gases and heart rate were continuously collected, with the final 3 min of data analysed. Ratings of Perceived Exertion and Omnibus-Resistance Exercise Scale were taken following each trial. Reliability was quantified by coefficient of variation (CV), intra-class correlation coefficients (ICC), smallest worthwhile change (SWC), and standard error of the measurement.ResultsMetabolic and cardiovascular variables were highly reliable (≤ 5% CV; excellent-moderate ICC), while the respiratory variables demonstrated moderate reliability (< 8% CV; good-moderate ICC) across both conditions. Perceptual ratings had poorer reliability during the Control condition (12–45% CV; poor ICC) than the Patrol condition (7–16% CV; good ICC).ConclusionsThe test–retest reliability of metabolic and cardiovascular variables was high and relatively consistent during load carriage. Respiratory responses demonstrated moderate test–retest reliability; however, as the SWC differed with load carriage tasks, such data should be interpreted independently across loads. Perceptual measures demonstrated poor to moderate reliability during load carriage, and it is recommended that they only be employed as secondary measures.Graphical abstract

Does carrying heavy loads impact ground reaction forces and plantar pressures in intervention police officers?

Background The main purpose of the study was to examine whether heavier loads might have an effect on ground reaction forces and plantar pressures. Methods Ninety-six elite intervention police officers were recruited in this cross-sectional study. Ground reaction forces and plantar pressures beneath the different foot regions were evaluated using Zebris FDM pressure platform, while a graduate increase in load carriage was as following: (i) ‘no load’, (ii) ‘a 5-kg load’, (iii) ‘a 25-kg load’ and (iv) ‘a 45-kg load’. Results Carrying heavier loads increased ground reaction forces beneath forefoot and hindfoot regions of both feet, and midfoot region for the right foot. For plantar pressures, increases beneath the hindfoot region of both feet and midfoot region of the right foot were observed, while carrying heavier loads. Conclusion This study shows significant increases in both ground reaction forces and plantar pressures, especially beneath the forefoot and hindfoot regions of both feet. Since the largest forces and pressures are produced beneath the hindfoot and forefoot, future research should pay special attention to these regions and their ground absorptions, additionally preventing from muscle and joint injuries.

Female manikin for the evaluation of breast support provided by sports bras

Introduction&#x0D; The effect of breast support on running biomechanics (Milligan, 2013) and breast pain on upper-extremity kinematics during running (White et al., 2015) is investigated by different research groups. They mostly found a higher implication for females with large breasts and showed that the use of sports bras is generally beneficial compared to regular bras. A well-fitted supportive sports bra can increase an athlete's performance (Fong &amp; Powell, 2022) and reduce the risk of injuries.&#x0D; The support properties of bras are conventionally evaluated by human trials. This is expensive and challenging when comparing the results of different studies.&#x0D; Methods&#x0D; Empa developed a manikin to investigate the load impact on the body (Wettenschwiler et al., 2017). This manikin was reshaped to a female upper body model equipped with breast prostheses for the realistic simulation of defined running conditions. A Polhemus motion tracking system was used to assess the relative movement of the manikin shell and the nipples during two simulated running conditions (8 km/h). A set of 16 sports bras was tested on the manikin regarding the reduction of relative movement of the nipples during running. In a first validation study, 6 of them were tested by human subjects during jogging (8 km/h) in 3 participants. The subjective support assessment was compared to the manikin data.&#x0D; Results&#x0D; A comparison of manikin measurement data (reduction in relative movement at 8 km/h) and subject data showed an excellent correlation (R2 &gt; 0.95) for the subjective support assessment.&#x0D; The sports bra developed in this project reached high marks regarding support, thermal comfort, and fit.&#x0D; Discussion/Conclusion&#x0D; Preliminary data indicates that the female manikin is able to provide objective data about breast movement in line with the perceived support of sports bras. In combination with additional methods such as sensory and thermal comfort assessment, this new methodology provides a scientific basis for developing improved sports bras meeting specific requirements for various sports.&#x0D; References&#x0D; Fong, H. B., &amp; Powell, D. W. (2022). Greater breast support is associated with reduced oxygen consumption and greater running economy during a rreadmill running task. Frontiers in Sports and Active Living, 4, Article 902276. https://doi.org/10.3389/fspor.2022.902276&#x0D; Milligan, A. K. (2013). The effect of breast support on running biomechanics [Doctoral Dissertation, University of Portsmouth].&#x0D; Wettenschwiler, P. D., Annaheim, S., Lorenzetti, S., Ferguson, S. J., Stämpfli, R., Psikuta, A., &amp; Rossi, R. M. (2017). Validation of an instrumented dummy to assess mechanical aspects of discomfort during load carriage. PLOS ONE, 12(6), Article e0180069. https://doi.org/10.1371/journal.pone.0180069&#x0D; White, J., Mills, C., Ball, N., &amp; Scurr, J. (2015). The effect of breast support and breast pain on upper-extremity kinematics during running: Implications for females with large breasts. Journal of Sports Sciences, 33(19), 2043-2050. https://doi.org/10.1080/02640414.2015.1026378

Metabolic Costs of Walking with Weighted Vests.

The US Army Load Carriage Decision Aid (LCDA) metabolic model is used by militaries across the globe and is intended to predict physiological responses, specifically metabolic costs, in a wide range of dismounted warfighter operations. However, the LCDA has yet to be adapted for vest-borne load carriage, which is commonplace in tactical populations, and differs in energetic costs to backpacking and other forms of load carriage. The purpose of this study is to develop and validate a metabolic model term that accurately estimates the effect of weighted vest loads on standing and walking metabolic rate for military mission-planning and general applications. Twenty healthy, physically active military-age adults (4 women, 16 men; age, 26 ± 8 yr old; height, 1.74 ± 0.09 m; body mass, 81 ± 16 kg) walked for 6 to 21 min with four levels of weighted vest loading (0 to 66% body mass) at up to 11 treadmill speeds (0.45 to 1.97 m·s -1 ). Using indirect calorimetry measurements, we derived a new model term for estimating metabolic rate when carrying vest-borne loads. Model estimates were evaluated internally by k -fold cross-validation and externally against 12 reference datasets (264 total participants). We tested if the 90% confidence interval of the mean paired difference was within equivalence limits equal to 10% of the measured walking metabolic rate. Estimation accuracy, precision, and level of agreement were also evaluated by the bias, standard deviation of paired differences, and concordance correlation coefficient (CCC), respectively. Metabolic rate estimates using the new weighted vest term were statistically equivalent ( P < 0.01) to measured values in the current study (bias, -0.01 ± 0.54 W·kg -1 ; CCC, 0.973) as well as from the 12 reference datasets (bias, -0.16 ± 0.59 W·kg -1 ; CCC, 0.963). The updated LCDA metabolic model calculates accurate predictions of metabolic rate when carrying heavy backpack and vest-borne loads. Tactical populations and recreational athletes that train with weighted vests can confidently use the simplified LCDA metabolic calculator provided as Supplemental Digital Content to estimate metabolic rates for work/rest guidance, training periodization, and nutritional interventions.