Load Carriage Research Articles

Does the impedance of above-knee powered prostheses need to be adjusted for load-carrying conditions?

Powered knee prostheses provide substantial advantages for amputees compared to traditional passive devices during basic walking tasks (i.e. level-ground, stairs, ramps), but the impedance control parameters are fixed. For environments that differ from the well-controlled setting of the clinic, amputees must compensate their gait patterns because fixed control parameters ideal for walking on level ground in the clinic do not meet real-life task demands. Load carriage is one instance where fixed control parameters may lead to undesired gait patterns and potentially result in injury. To evaluate the importance of impedance control parameters for different walking tasks, we tested one above-knee amputee walking using an experimental powered prosthesis under four walking conditions. The amputee walked with and without added mass with both load-specific and non-specific impedance control parameters. The load-specific parameters significantly reduced the amputee's intact-leg compensations, asymmetry, and perceived exertion compared to the non-specific control parameters. Powered lower limb prostheses that modulate impedance control parameters for load-carrying tasks may improve the gait performance, safety, and comfort of amputees.

Influence of a 12.8-km military load carriage activity on lower limb gait mechanics and muscle activity

The high stress fracture occurrence in military populations has been associated with frequent load carriage activities. This study aimed to assess the influence of load carriage and of completing a load carriage training activity on gait characteristics. Thirty-two Royal Marine recruits completed a 12.8-km load carriage activity as part of their military training. Data were collected during walking in military boots, pre and post-activity, with and without the additional load (35.5 kg). Ground contact time, lower limb sagittal plane kinematics and kinetics, and electromyographic variables were obtained for each condition. When carrying load, there was increased ground contact time, increased joint flexion and joint moments, and increased plantar flexor and knee extensor muscle activity. Post-activity, there were no changes to kinematic variables, knee extensor moments were reduced, and there was evidence of plantar flexor muscle fatigue. The observed gait changes may be associated with stress fracture development.Practitioner Summary: This study identified gait changes due to load carriage and after a military load carriage training activity. Such activities are associated with lower limb stress fractures. A pre–post study design was used. Gait mechanics changed to a greater extent when carrying load, than after completion of the activity when assessed without load.

Relative contribution of articular cartilage\u2019s constitutive components to load support depending on strain rate

Cartilage is considered a biphasic material in which the solid is composed of proteoglycans and collagen. In biphasic tissue, the hydraulic pressure is believed to bear most of the load under higher strain rates and its dissipation due to fluid flow determines creep and relaxation behavior. In equilibrium, hydraulic pressure is zero and load bearing is transferred to the solid matrix. The viscoelasticity of the collagen network also contributes to its time-dependent behavior, and the osmotic pressure to load bearing in equilibrium. The aim of the present study was to determine the relative contributions of hydraulic pressure, viscoelastic collagen stress, solid matrix stiffness and osmotic pressure to load carriage in cartilage under transient and equilibrium conditions. Unconfined compression experiments were simulated using a fibril-reinforced poroviscoelastic model of articular cartilage, including water, fibrillar viscoelastic collagen and non-fibrillar charged glycosaminoglycans. The relative contributions of hydraulic and osmotic pressures and stresses in the fibrillar and non-fibrillar network were evaluated in the superficial, middle and deep zone of cartilage under five different strain rates and after relaxation. Initially upon loading, the hydraulic pressure carried most of the load in all three zones. The osmotic swelling pressure carried most of the equilibrium load. In the surface zone, where the fibers were loaded in tension, the collagen network carried 20 % of the load for all strain rates. The importance of these fibers was illustrated by artificially modifying the fiber architecture, which reduced the overall stiffness of cartilage in all conditions. In conclusion, although hydraulic pressure dominates the transient behavior during cartilage loading, due to its viscoelastic nature the superficial zone collagen fibers carry a substantial part of the load under transient conditions. This becomes increasingly important with higher strain rates. The interesting and striking new insight from this study suggests that under equilibrium conditions, the swelling pressure generated by the combination of proteoglycans and collagen reinforcement accounts cartilage stiffness for more than 90 % of the loads carried by articular cartilage. This finding is different from the common thought that load is transferred from fluid to solid and is carried by the aggregate modulus of the solid. Rather, it is transformed from hydraulic to osmotic swelling pressure. These results show the importance of considering both (viscoelastic) collagen fibers as well as swelling pressure in studies of the (transient) mechanical behavior of cartilage.

The impact of thoracic load carriage up to 45kg on the cardiopulmonary response to exercise.

The purposes of this experiment were to, first, document the effect of 45-kg thoracic loading on peak exercise responses and, second, the effects of systematic increases in thoracic load on physiological responses to submaximal treadmill walking at a standardized speed and grade. On separate days, 19 males (age 27±5years, height 180.0±7.4cm, mass 86.9±15.1kg) completed randomly ordered graded exercise tests to exhaustion in loaded (45kg) and unloaded conditions. On a third day, each subject completed four randomly ordered, 10-min bouts of treadmill walking at 1.34ms(-1) and 4% grade in the following conditions: unloaded, and with backpacks weighted to 15, 30, and 45kg. With 45-kg thoracic loading, absolute oxygen consumption ([Formula: see text]), minute ventilation, power output, and test duration were significantly decreased at peak exercise. End-inspiratory lung volume and tidal volume were significantly reduced with no changes in end-expiratory lung volume, breathing frequency, and the respiratory exchange ratio. Peak end-tidal carbon dioxide and the ratio of alveolar ventilation to carbon dioxide production were similar between conditions. The reductions in peak physiological responses were greater than expected based on previous research with lighter loads. During submaximal treadmill exercise, [Formula: see text] increased (P<0.05) by 11.0 (unloaded to 15kg), 14.5 (15-30kg), and 18.0% (30-45kg) showing that the increase in exercise [Formula: see text] was not proportional to load mass. These results provide further insight into the specificity of physiological responses to different types of load carriage.

Effects of load mass carried in a backpack upon respiratory muscle fatigue

Purpose: The purpose of this study was to investigate whether loads carried in a backpack, with a load mass ranging from 0 to 20 kg, causes respiratory muscle fatigue. Methods: Eight males performed four randomised load carriage (LC) trials comprising 60 min walking at 6.5 km h−1 wearing a backpack of either 0 (LC0), 10 (LC10), 15 (LC15) or 20 kg (LC20). Inspiratory (PImax) and expiratory (PEmax) mouth pressures were assessed prior to and immediately following each trial. Pulmonary gas exchange, heart rate (HR), blood lactate and glucose concentration and perceptual responses were recorded during the first and final 60 s of each trial. Results: Group mean PImax and PEmax were unchanged following 60-min load carriage in all conditions (p > .05). There was an increase over time in pulmonary gas exchange, HR and perceptions of effort relative to baseline measures during each trial (p < .05) with changes not different between trials (p > .05). Conclusions: These findings indicate that sub-maximal walking with no load or carrying 10, 15 or 20 kg in a backpack for up to 60 min does not cause respiratory muscle fatigue despite causing an increase in physiological, metabolic and perceptual parameters.

Effects of thigh holster use on kinematics and kinetics of active duty police officers

BackgroundBody armour, duty belts and belt mounted holsters are standard equipment used by the Swedish police and have been shown to affect performance of police specific tasks, to decrease mobility and to potentially influence back pain. This study aimed to investigate the effects on gait kinematics and kinetics associated with use of an alternate load carriage system incorporating a thigh holster. MethodsKinematic, kinetic and temporospatial data were collected using three dimensional gait analysis. Walking tests were conducted with nineteen active duty police officers under three different load carriage conditions: a) body armour and duty belt, b) load bearing vest, body armour and thigh holster and c) no equipment (control). FindingsNo significant differences between testing conditions were found for temporospatial parameters. Range of trunk rotation was reduced for both load carriage conditions compared to the control condition (p<0.017). Range of hip rotation was more similar to the control condition when wearing thigh holster rather than the belt mounted hip holster (p<0.017). Moments and powers for both left and right ankles were significantly greater for both of the load carriage conditions compared to the control condition (p<0.017). InterpretationThis study confirms that occupational loads carried by police have a significant effect on gait kinematics and kinetics. Although small differences were observed between the two load carriage conditions investigated in this study, results do not overwhelmingly support selection of one design over the other.

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

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

Effects of exercise mode, energy, and macronutrient interventions on inflammation during military training.

Load carriage (LC) exercise may exacerbate inflammation during training. Nutritional supplementation may mitigate this response by sparing endogenous carbohydrate stores, enhancing glycogen repletion, and attenuating negative energy balance. Two studies were conducted to assess inflammatory responses to acute LC and training, with or without nutritional supplementation. Study 1: 40 adults fed eucaloric diets performed 90‐min of either LC (treadmill, mean ± SD 24 ± 3 kg LC) or cycle ergometry (CE) matched for intensity (2.2 ± 0.1 VO2peak L min−1) during which combined 10 g protein/46 g carbohydrate (223 kcal) or non‐nutritive (22 kcal) control drinks were consumed. Study 2: 73 Soldiers received either combat rations alone or supplemented with 1000 kcal day−1 from 20 g protein‐ or 48 g carbohydrate‐based bars during a 4‐day, 51 km ski march (~45 kg LC, energy expenditure 6155 ± 515 kcal day−1 and intake 2866 ± 616 kcal day−1). IL‐6, hepcidin, and ferritin were measured at baseline, 3‐h post exercise (PE), 24‐h PE, 48‐h PE, and 72‐h PE in study 1, and before (PRE) and after (POST) the 4‐d ski march in study 2. Study 1: IL‐6 was higher 3‐h and 24‐h post exercise (PE) for CE only (mode × time, P < 0.05), hepcidin increased 3‐h PE and recovered by 48‐h, and ferritin peaked 24‐h and remained elevated 72‐h PE (P < 0.05), regardless of mode and diet. Study 2: IL‐6, hepcidin and ferritin were higher (P < 0.05) after training, regardless of group assignment. Energy expenditure (r = 0.40), intake (r = −0.26), and balance (r = −0.43) were associated (P < 0.05) with hepcidin after training. Inflammation after acute LC and CE was similar and not affected by supplemental nutrition during energy balance. The magnitude of hepcidin response was inversely related to energy balance suggesting that eating enough to balance energy expenditure might attenuate the inflammatory response to military training.

Load carriage, human performance, and employment standards.

The focus of this review is on the physiological considerations necessary for developing employment standards within occupations that have a heavy reliance on load carriage. Employees within military, fire fighting, law enforcement, and search and rescue occupations regularly work with heavy loads. For example, soldiers often carry loads >50 kg, whilst structural firefighters wear 20-25 kg of protective clothing and equipment, in addition to carrying external loads. It has long been known that heavy loads modify gait, mobility, metabolic rate, and efficiency, while concurrently elevating the risk of muscle fatigue and injury. In addition, load carriage often occurs within environmentally stressful conditions, with protective ensembles adding to the thermal burden of the workplace. Indeed, physiological strain relates not just to the mass and dimensions of carried objects, but to how those loads are positioned on and around the body. Yet heavy loads must be borne by men and women of varying body size, and with the expectation that operational capability will not be impinged. This presents a recruitment conundrum. How do employers identify capable and injury-resistant individuals while simultaneously avoiding discriminatory selection practices? In this communication, the relevant metabolic, cardiopulmonary, and thermoregulatory consequences of loaded work are reviewed, along with concomitant impediments to physical endurance and mobility. Also emphasised is the importance of including occupation-specific clothing, protective equipment, and loads during work-performance testing. Finally, recommendations are presented for how to address these issues when evaluating readiness for duty.

Towards best practice in physical and physiological employment standards.

While the scope of the term physical employment standards is wide, the principal focus of this paper is on standards related to physiological evaluation of readiness for work. Common applications of such employment standards for work are in public safety and emergency response occupations (e.g., police, firefighting, military), and there is an ever-present need to maximize the scientific quality of this research. Historically, most of these occupations are male-dominated, which leads to potential sex bias during physical demands analysis and determining performance thresholds. It is often assumed that older workers advance to positions with lower physical demand. However, this is not always true, which raises concerns about the long-term maintenance of physiological readiness. Traditionally, little attention has been paid to the inevitable margin of uncertainty that exists around cut-scores. Establishing confidence intervals around the cut-score can reduce for this uncertainty. It may also be necessary to consider the effects of practise and biological variability on test scores. Most tests of readiness for work are conducted under near perfect conditions, while many emergency responses take place under far more demanding and unpredictable conditions. The potential impact of protective clothing, respiratory protection, load carriage, environmental conditions, nutrition, fatigue, sensory deprivation, and stress should also be considered when evaluating readiness for work. In this paper, we seek to establish uniformity in terminology in this field, identify key areas of concern, provide recommendations to improve both scientific and professional practice, and identify priorities for future research.

Performance of a lateral pelvic cluster technical system in evaluating running kinematics

Valid measurement of pelvic and hip angles during posterior load carriage gait task requires placement of pelvic markers which will not be occluded or physically displaced by the load. One solution is the use of pure lateral pelvic clusters to track the pelvis segment. However, the validity of this method has not been compared against pelvic marker systems recommended by the International Society of Biomechanics (ISB) during high impact tasks, such as running. The purpose of this study was to validate the lateral tracking pelvic clusters against the ISB pelvis during running. Six participants performed overground running at a self-selected running speed with shoes. Three dimensional motion capture and synchronised in-ground force plates were used to determine lower limb joint angles and gait events respectively. Two biomechanical models were used to derive pelvic segment and hip joint angles. The ISB pelvis used the anterior and posterior iliac spines as anatomical and tracking markers, whilst the other model used lateral pelvic clusters as tracking markers. The between participant averaged coefficient of multiple correlation suggested good to excellent agreement between the angle waveforms generated from the two marker protocols. In addition, both marker protocols had similar sensitivity in detecting three dimensional pelvic and hip joint angles during the stance phase. This study suggests that in the event posterior load carriage is involved in running gait, pelvic and hip kinematics can be measured by the use of lateral pelvic clusters.

Reducing Dynamic Loads From a Backpack During Load Carriage Using an Upper Body Assistive Device

This paper presents studies of an upper body assistive device designed to aid human load carriage. The two primary functions of the device are: (i) distributing the backpack load between the shoulders and the waist and (ii) reducing the dynamic load of a backpack on the human body during walking. These functions are targeted to relieve stress applied on the shoulders and the back, and also reduce the dynamic loads transferred to the lower limbs during walking. These functions are achieved by incorporating two modules—passive and active—within a custom fitted shirt integrated with motion/force sensors, actuators, and a real-time controller. The relevant modeling and controller design are presented for dynamic load compensation. Preliminary evaluation of the device was first performed on a single subject, followed by a pilot study with ten healthy subjects walking on a treadmill with a backpack. Results show that the device can effectively transfer the load from the shoulders to the waist and also reduce the dynamic loads induced by the backpack during walking. Reduction in peak and total normal ground reaction forces, leg muscle activations, and oxygen consumptions was observed with the device. This suggests that the device can potentially reduce the risk of musculoskeletal injuries and fatigue on the lower limbs associated with carrying heavy loads and provide some metabolic benefits.

Predicting Soldier Load Carriage Performance

Completing a load carriage (LC) task is the best method for assessing a recruit’s potential to perform this critical Soldiering task, but the use of physical fitness tests (PFTs) to predict their potential is more time efficient and may mitigate injury risk. PURPOSE: To determine the relationship between PFTs and walking LC performance. METHODS: While wearing ~46.7 kg load, 553 male and 230 female Soldiers performed a 4-mile LC on flat terrain. Soldiers also performed 14 PFTs while wearing shorts, t-shirts and athletic shoes including: 1-minute push-ups, Handgrip, 2-minute Arm Ergometer (AE), 38 cm Upright Pull (UP), Isometric Bicep Curl (IBC), Medicine Ball Put (MBP), Dumbbell Squat Lift (SL), Standing Long Jump (LJ), 300 m Sprint (SP), Illinois Agility test (IA), Beep Test (BT), 9 kg Powerball Throw (PBT), 20 m Sled Drag (RP), and 1-minute sit-ups. RESULTS: Time to complete LC was 75.7 ± 7.6 min (mean ± SD). All PFTs were significantly correlated (Pearson’s r) with LC time: push-ups, -0.49; HG, -0.49; AE, -0.54; UP, -0.52; IBC, -0.53; MBP, -0.56; SL, -0.54; SP, 0.53; IA, 0.35; LJ, -0.45; BT, -0.46; PBT, -0.56; RP, -0.55; sit-ups, -0.18. A stepwise multiple regression was used to develop the following equation (SEE = 8:27 min:sec): LC(min)=119.197 – 1.727 (MBP m) – 0.132 (BT s) – 0.109 (SL kg) – 0.034 (AE rev/min) – 4.344 (RP m/sec). The equation explained 43% of the variability (R2) of LC times (p < 0.01). CONCLUSIONS: A Soldier’s potential to complete the LC can be predicted by a model using 5 PFTs. Using these simple PFTs to assess an individual’s performance on a physically demanding task would be more time efficient and may decrease injury risks. The views expressed in this abstract are those of the authors and do not reflect the official policy of the Department of Army, Department of Defense, or the U.S. Government.

Influence of Load Carriage on High-Intensity Running Performance Estimation.

Load carriage is a necessary burden for tactical athletes. A combination of training modes, including aerobic conditioning and progressive load carriage, may lead to improved performance. The critical speed (CS) concept enables the practitioner to prescribe high-intensity interval training (HIIT) time limits (TLIMs) from a single 3-minute all-out exercise test (3 MT). We sought to examine the effect of a standard load carriage (18.86 kg) on CS and the finite running capacity > CS (D'). A group of trained subjects (age: 26 ± 5 years, height: 181 ± 4 cm, body mass [BM]: 90 ± 14 kg) completed a loaded and unloaded (UL) 3 MT. The CS was reduced by 0.66 ± 0.24 m·s (p < 0.01) in the loaded condition. There was a small nonsignificant increase in D' (21.25 ± 39.53 m, p = 0.07). The higher the % load carriage relative to BM is, the greater decline in CS (r = 0.83, p < 0.01). A revised CS with load carriage from the UL 3 MT may be calculated using: adjusted CS = original CS + ([-0.0638 × %load]) + 0.6982. Our results indicate that revised CS and TLIMs for fixed distance, fixed time, or fixed speed HIIT prescriptions may be derived from a UL 3 MT. Such calculations would enable more expeditious training for tactical athletes. We recommend further research involving implementation of HIIT using this new method.

Functional Inspiratory Muscle Training (IMT) Improves Load Carriage Performance Greater than Traditional IMT Techniques

The addition of thoracic loads is common in occupational groups such as the military. The positioning upon the thorax poses a unique challenge to breathing mechanics and causes respiratory muscle fatigue (RMF) following exercise. IMT techniques provide a positive impact to exercise performance as well as attenuating RMF in both health and athletic populations. However in occupational groups, despite increased inspiratory muscle strength and performance, IMT has failed to attenuate RMF, potentially limiting the performance enhancement of IMT. It has been suggested that functional inspiratory muscle training (IMTF) may elicit adaptations above that of traditional IMT techniques as it targets the inspiratory muscles throughout the length-tension range adopted during exercise. PURPOSE: To investigate the use IMTF techniques on performance in exercise tasks with thoracic load carriage. METHODS: All participants (n=17) completed 4-week foundation IMT using a Powerbreathe device (2 x 30 breaths, daily at 50% maximal inspiratory pressure (MIP), either side of a pre-loaded time-trial (LCTT) while carrying a 25 kg thoracic load. Participants were randomly assigned to either IMTF (n=9) or a maintenance group (CON, n=8) and completed 4 additional weeks of training. IMTF consisted of 3 sessions per week whilst simultaneously breathing through the training device at 50% MIP and conducting 4 predetermined core exercises. CON, comprised of 30 breaths at 50% MIP, 3 times weekly. RESULTS: Baseline LCTT was 15.93 ± 2.30 and improved to 14.73 ± 2.40 min post 4 week IMT LCTT (P &lt0.01). Post IMTF, LCTT further improved (13.59 ± 2.33 min, P &lt0.05). Relative to baseline (151 ± 36 cmH2O), MIP was greater post IMT (172 ± 39 cmH2O, P<0.05) but was similar post IMTF (179 ± 25 cmH2O, P >0.05) and CON (P>0.05). The post exercise reduction in MIP in all trials remained unchanged. CONCLUSION: IMT improves MIP and exercise performance with thoracic load carriage and the improvement is enhanced by incorporating a period of IMTF, which provides an additional ergogenic effect to exercise performance. This appears to be the result of improved coordination between core and respiratory muscle groups that are tasked heavily via load carriage exercise and IMTF. However, it did not attenuate respiratory muscle fatigue after load carriage activities.

High Load And Intensity But Low Volume

PURPOSE: To determine the efficacy of a high load and intensity experimental physical training regimen to improve recruit performance within the Australian Army. METHODS: Military recruits were assigned to either a 12-week Experimental (EXP n = 68, 21.7 ± 4.2 y), Military (MIL n = 60, 21.1 ± 4.1 y) or civilians act as a control group (CON n = 11, 25.5 ± 4.5 y) and were assessed at Weeks 1, 6 and 12, in military tests for 3.2 km 22 kg load carriage, 1RM 1.5m box lift, 20 m multistage fitness test and 2 min push-up test. A random sub-sample of recruits (EXP n = 33; MIL n = 38) also performed physiological tests (DEXA, V [Combining Dot Above]O2peak, 1RM squat and bench press, vertical jump and 30 s Wingate). Total training time (41 hours) and frequency (41) was match between EXP and MIL. However, compared to MIL the EXP had 50% lower physical activity count (triaxial accelerometer), but higher heart rate reserve (heart rate monitor, EXP >70%, MIL 15RM). Significant interactions (P<0.05) are reported as the mean change between Weeks 1 and 12, ± SD. RESULTS: No changes were observed for CON. EXP significantly reduced total body fat (EXP -2.7 ± 2.2 kg, MIL -1.7 ± 2.2 kg) whilst total lean mass was observed to increase in both groups (EXP 2.1 ± 1.9 kg, MIL 2.4 ± 2.2 kg). EXP showed superior improvement in load carriage time (EXP -155.1 ± 122.4 s, MIL -104.1 ± 123.6 s), 1RM box lift (EXP 4.8 ± 6.0 kg, MIL 1.0 ± 5.5 kg), 20 m multistage fitness test (EXP 5.3 ± 4.1 mL.kg-1.min-1, MIL 3.4 ± 4.0 mL.kg-1.min-1), 2-min push-up (EXP 10.8 ± 7.1 reps, MIL 8.0 ± 7.4 reps), 1RM bench press (EXP 18.0 ± 6.7 kg, MIL 9.2 ± 18.6 kg), 1RM squat (EXP 27.8 ± 10.5 kg, MIL -6.1 ± 27.6 kg) and V [Combining Dot Above]O2peak (EXP 2.7 ± 4.1 mL.kg-1.min-1, MIL -1.2 ± 6.3 mL.kg-1.min-1). MIL had a significantly greater decline in vertical jump power (EXP -36.8 ± 128.7 W, MIL -72.1 ± 139.4 W). In contrast, 30 s mean power declined in both groups after training (EXP -24.5 ± 53.7 W, MIL -25.0 ± 107.7 W). CONCLUSION: Despite a significant reduction in training volume, recruit performance in basic military, occupational and physiological tests of physical fitness were superior. Our results suggest that high resistance training loads and exercise endurance intensity can be successfully implemented within a mass military recruit training environment. Supported by a UOW/DST Group doctoral scholarship

Inflammation And Hepcidin Responses To Nutritional Supplementation During Load Carriage And Short-term Military Training

Inflammation And Hepcidin Responses To Nutritional Supplementation During Load Carriage And Short-term Military Training

Impact of Redistributing Torso-borne Loads on Soldier Muscular Cost

Previous studies have identified significant reductions in lumbar strength measures following prolonged torso-borne load carriage. A proposed solution to mitigate the negative impact of bearing mass on the shoulders and upper back is to utilize a device designed to redistribute the load to the pelvic region. PURPOSE: To assess the impact of redistributing torso-borne military loads from the shoulders to the pelvic region with a load distribution device (LDD) on lumbar muscle strength of the load carrier after a prolonged march. METHODS: Fourteen Soldiers conducted 2-h prolonged marches at 1.34 m·s-1 under two conditions: a baseline condition consisting of a 29.7-kg fighting load with no redistribution and a condition utilizing the LDD to alter the distribution of the fighting load to a high level (70-90%) of shoulder offloading. Flexible pressure sensors were placed on the shoulders to establish and verify the level of offloading relative to the baseline condition. Isokinetic lumbar muscle flexion and extension data were collected immediately before and after the marches for 5 maximal muscle contractions at 20°·s-1. Total work (N·m) and average power (W) were calculated over the 5 repetitions and the delta (pre- minus post-march) was determined. A one-way, repeated measures ANOVA (p < 0.05) was performed to assess the effects of redistributing the torso-borne load on lumbar total work delta and average power delta. RESULTS: Lumbar pre- minus post-march muscle strength scores revealed significant differences in isokinetic lumbar flexion, reflecting smaller decreases in both total work performed (2.3 N·m, p=0.012) and average power generated (0.274 W, p=0.046) after the prolonged march for the high offloading condition versus the no offloading condition. No statistical differences were found for lumbar extension. CONCLUSIONS: Redistributing load from the shoulders to the pelvic region with an LDD reduces the muscular cost of the lumbar flexor muscles associated with prolonged load carriage. Preserving this localized strength may improve Soldier mission effectiveness following long marches. Supported by NSRDEC.

Tibia Bone Strain Distribution during Incremented Load Carriage

Tibia Bone Strain Distribution during Incremented Load Carriage

The Pandolf load carriage equation is a poor predictor of metabolic rate while wearing explosive ordnance disposal protective clothing

This investigation aimed to quantify metabolic rate when wearing an explosive ordnance disposal (EOD) ensemble (~33kg) during standing and locomotion; and determine whether the Pandolf load carriage equation accurately predicts metabolic rate when wearing an EOD ensemble during standing and locomotion. Ten males completed 8 trials with metabolic rate measured through indirect calorimetry. Walking in EOD at 2.5, 4.0 and 5.5km·h−1 was significantly (p < 0.05) greater than matched trials without the EOD ensemble by 49% (127W), 65% (213W) and 78% (345W), respectively. Mean bias (95% limits of agreement) between predicted and measured metabolism during standing, 2.5, 4 and 5.5km·h−1 were 47W (19 to 75W); −111W (−172 to −49W); −122W (−189 to −54W) and −158W (−245 to −72W), respectively. The Pandolf equation significantly underestimated measured metabolic rate during locomotion. These findings have practical implications for EOD technicians during training and operation and should be considered when developing maximum workload duration models and work-rest schedules.Practitioner Summary: Using a rigorous methodological design we quantified metabolic rate of wearing EOD clothing during locomotion. For the first time we demonstrated that metabolic rate when wearing this ensemble is greater than that predicted by the Pandolf equation. These original findings have significant implications for EOD training and operation.