A systematic literature review of evidence for the use of assistive exoskeletons in defence and security use cases

Advances in assistive exoskeleton technology, and a boom in related scientific literature, prompted a need to review the potential use of exoskeletons in defence and security. A systematic review examined the evidence for successful augmentation of human performance in activities deemed most relevant to military tasks. Categories of activities were determined a priori through literature scoping and Human Factors workshops with military stakeholders. Workshops identified promising opportunities and risks for integration of exoskeletons into military use cases. The review revealed promising evidence for exoskeletons' capacity to assist with load carriage, manual lifting, and working with tools. However, the review also revealed significant gaps in exoskeleton capabilities and likely performance levels required in the use case scenarios. Consequently, it was recommended that a future roadmap for introducing exoskeletons to military environments requires development of performance criteria for exoskeletons that can be used to implement a human-centred approach to research and development.

Do non-rearfoot runners experience greater second metatarsal stresses than rearfoot runners?

Stress fracture of the second metatarsal is a common and problematic injury for runners. The choice of foot strike pattern is known to affect external kinetics and kinematics but its effect on internal loading of the metatarsals is not well understood. Models of various complexities can be used to investigate the effects of running characteristics on metatarsal stresses. This study aimed to compare second metatarsal stress between habitual rearfoot and non-rearfoot strikers during barefoot running, using a novel participant-specific finite element model, including accurate metatarsal and soft tissue geometry. Synchronised force and kinematic data were collected during barefoot overground running from 20 participants (12 rearfoot strikers). Stresses were calculated using a previously evaluated and published 3D finite element model. Non-rearfoot strikers demonstrated greater external loading and joint contact forces than rearfoot runners, but there were no differences in stresses between groups. Additionally, the study allowed for a qualitative assessment of bone geometries and stresses. No correlation was found between bone volume and stresses, however, there was found to be a large variation in metatarsal shapes, possibly accounting for the lack of difference in stresses. This emphasises the importance of bone geometry when estimating bone stress and supports the suggestion that external forces should not be assumed to be representative of internal loading.

Biomechanical Basis of Predicting and Preventing Lower Limb Stress Fractures During Arduous Training

PURPOSE OF REVIEW

Stress fractures at weight-bearing sites, particularly the tibia, are common in military recruits and athletes. This review presents recent findings from human imaging and biomechanics studies aimed at predicting and preventing stress fractures.

RECENT FINDINGS

Peripheral quantitative computed tomography (pQCT) provides evidence that cortical bone geometry (tibial width and area) is associated with tibial stress fracture risk during weight-bearing exercise. The contribution of bone trabecular microarchitecture, cortical porosity, and bone material properties in the pathophysiology of stress fractures is less clear, but high-resolution pQCT and new techniques such as impact microindentation may improve our understanding of the role of microarchitecture and material properties in stress fracture prediction. Military studies demonstrate osteogenic outcomes from high impact, repetitive tibial loading during training. Kinetic and kinematic characteristics may influence stress fracture risk, but there is no evidence that interventions to modify biomechanics can reduce the incidence of stress fracture. Strategies to promote adaptive bone formation, in combination with improved techniques to assess bone strength, present exciting opportunities for future research to prevent stress fractures.

Physiological demands of running at 2-hour marathon race pace

The requirements of running a 2-h marathon have been extensively debated but the actual physiological demands of running at ∼21.1 km/h have never been reported. We therefore conducted laboratory-based physiological evaluations and measured running economy (O₂ cost) while running outdoors at ∼21.1 km/h, in world-class distance runners as part of Nike's "Breaking 2" marathon project. On separate days, 16 world-class male distance runners (age, 29 ± 4 yr; height, 1.72 ± 0.04 m; mass, 58.9 ± 3.3 kg) completed an incremental treadmill test for the assessment of V̇O_2peak, O₂ cost of submaximal running, lactate threshold and lactate turn-point, and a track test during which they ran continuously at 21.1 km/h. The laboratory-determined V̇O_2peak was 71.0 ± 5.7 mL/kg/min with lactate threshold and lactate turn-point occurring at 18.9 ± 0.4 and 20.2 ± 0.6 km/h, corresponding to 83 ± 5% and 92 ± 3% V̇O_2peak, respectively. Seven athletes were able to attain a steady-state V̇O₂ when running outdoors at 21.1 km/h. The mean O₂ cost for these athletes was 191 ± 19 mL/kg/km such that running at 21.1 km/h required an absolute V̇O₂ of ∼4.0 L/min and represented 94 ± 3% V̇O_2peak. We report novel data on the O₂ cost of running outdoors at 21.1 km/h, which enables better modeling of possible marathon performances by elite athletes. Using the value for O₂ cost measured in this study, a sub 2-h marathon would require a 59 kg runner to sustain a V̇O₂ of approximately 4.0 L/min or 67 mL/kg/min.NEW & NOTEWORTHY We report the physiological characteristics and O₂ cost of running overground at ∼21.1 km/h in a cohort of the world's best male distance runners. We provide new information on the absolute and relative O₂ uptake required to run at 2-h marathon pace.

Tibial stress during running following a repeated calf-raise protocol

Tibial stress fractures are a problematic injury among runners. Increased loading of the tibia has been observed following prolonged weight-bearing activity and is suggested to be the result of reduced activity of the plantar flexor muscles. The musculature that spans the tibia contributes to bending of the bone and influences the magnitude of stress on the tibia during running. Participant-specific models of the tibia can be used as a non-invasive estimate of tibial stress. This study aimed to quantify tibial stress during running using participant-specific bone geometry and to compare tibial stress before and after a protocol of repeated muscular contractions of the plantar flexor muscle group. Fourteen participants who run recreationally were included in the final analysis of the study. Synchronized force and kinematic data were collected during overground running before and after an exhaustive, weighted calf-raise protocol. Bending moments and stress at the distal third of the tibia were estimated using beam theory combined with inverse dynamics and musculoskeletal modeling. Bone geometry was obtained from magnetic resonance images. There was no difference in stress at the anterior, posterior, medial, or lateral peripheries of the tibia after the calf-raise protocol compared with before. These findings suggest that an exhaustive, repeated calf-raise protocol did not alter tibial stress during running.

Footwear Matters: Influence of Footwear and Foot Strike on Load Rates during Running

INTRODUCTION

Running with a forefoot strike (FFS) pattern has been suggested to reduce the risk of overuse running injuries, due to a reduced vertical load rate compared with rearfoot strike (RFS) running. However, resultant load rate has been reported to be similar between foot strikes when running in traditional shoes, leading to questions regarding the value of running with a FFS. The influence of minimal footwear on the resultant load rate has not been considered. This study aimed to compare component and resultant instantaneous loading rate (ILR) between runners with different foot strike patterns in their habitual footwear conditions.

METHODS

Twenty-nine injury-free participants (22 men, seven women) ran at 3.13 m·s along a 30-m runway, with their habitual foot strike and footwear condition. Ground reaction force data were collected. Peak ILR values were compared between three conditions; those who habitually run with an RFS in standard shoes, with an FFS in standard shoes, and with an FFS in minimal shoes.

RESULTS

Peak resultant, vertical, lateral, and medial ILR were lower (P < 0.001) when running in minimal shoes with an FFS than in standard shoes with either foot strike. When running with an FFS, peak posterior ILR were lower (P < 0.001) in minimal than standard shoes.

CONCLUSIONS

When running in a standard shoe, peak resultant and component ILR were similar between footstrike patterns. However, load rates were lower when running in minimal shoes with a FFS, compared with running in standard shoes with either foot strike. Therefore, it appears that footwear alters the load rates during running, even with similar foot strike patterns.

Why forefoot striking in minimal shoes might positively change the course of running injuries

It is believed that human ancestors evolved the ability to run bipedally approximately 2 million years ago. This form of locomotion may have been important to our survival and likely has influenced the evolution of our body form. As our bodies have adapted to run, it seems unusual that up to 79% of modern day runners are injured annually. The etiology of these injuries is clearly multifactorial. However, 1 aspect of running that has significantly changed over the past 50 years is the footwear we use. Modern running shoes have become increasingly cushioned and supportive, and have changed the way we run. In particular, they have altered our footstrike pattern from a predominantly forefoot strike (FFS) landing to a predominantly rearfoot strike (RFS) landing. This change alters the way in which the body is loaded and may be contributing to the high rate of injuries runners experience while engaged in an activity for which they were adapted. In this paper, we will examine the benefits of barefoot running (typically an FFS pattern), and compare the lower extremity mechanics between FFS and RFS. The implications of these mechanical differences, in terms of injury, will be discussed. We will then provide evidence to support our contention that FFS provides an optimal mechanical environment for specific foot and ankle structures, such as the heel pad, the plantar fascia, and the Achilles tendon. The importance of footwear will then be addressed, highlighting its interaction with strike pattern on mechanics. This analysis will underscore why footwear matters when assessing mechanics. Finally, proper preparation and safe transition to an FFS pattern in minimal shoes will be emphasized. Through the discussion of the current literature, we will develop a justification for returning to running in the way for which we were adapted to reduce running-related injuries.

Ectopic splenic tissue failed to prevent fatal pneumococcal septicaemia after splenectomy for trauma

Despite heterotopic splenic tissue, fatal fulminating pneumococcal septicaemia occurred in 2 patients who had had splenectomy for trauma. A girl aged 12 who died 8 years after splenectomy had over a hundred nodules, the largest weighing 3 g. A man of 19 who died 9 years after splenectomy had splenic tissue weighing 92 g. The presence of splenic tissue did not itself protect these patients from overwhelming infection and its ectopic situation with the consequent alteration in blood-supply may be of greater importance than the amount of splenic tissue present.

Rupture of the jejunum due to faulty infant-feeding techniques

An eight-month old infant, thought to have died of gastroenteritis, was found to have general peritonitis, due to rupture of the proximal jejunum. This and other injuries, initially suspected of being non-accidental, were due to the father's practice of forcible compression of the upper abdomen after feeds, to make the baby bring up bile, as well as wind, before being put down. Full investigation led to the conclusion that there had been no conscious intention of hurting the infant and that the injuries were not non-accidental in the accepted sense. One more condition must be added to the differential diagnosis of abdominal upsets in infants.

The first thought of the pathologist who discovers unsuspected skeletal or visceral injuries at the autopsy of an infant must be that their probable cause was non-accidental injury. Any other explanation must satisfy full police investigations and will rarely be acceptable. A case is reported in which the authorities were satisfied that the injuries were the result of a misconceived practice associated with infantfeeding and were inflicted with no concious intention of harming the infant.

Carboxyhaemoglobin dissociation in the cadaver following attempted resuscitation

A series of 300 cases of fatal carbon-monoxide poisoning showed wide variations in carboxyhaemoglobin saturation. Levels below 50% in 24 subjects under the age of 70 were probably falsely low following attempted resuscitation on the way to hospital. Artificial respiration, especially with oxygen-rich gas, causes dissociation of carboxyhaemoglobin in the lungs of the cadaver while movement of blood into and out of the lungs, with mixing, lowers the saturation levels in the neighbouring large veins. In four cases subclavian blood showed saturation levels much lower than blood from sites further from the lungs. Blood should be taken from the femoral vein to get true readings.