Focal muscle spasticity has little impact on muscle power for walking in people with Traumatic Brain Injury.

BACKGROUND: Spasticity is prevalent following Traumatic Brain Injury. 'Focal' muscle spasticity has been defined as spasticity affecting a localised muscle group, but it's impact on gait kinetics remains unclear. The aim of this study was to investigate the relationship between focal muscle spasticity and gait kinetics following Traumatic Brain Injury. METHODS: Ninety-three participants attending physiotherapy for mobility limitations following Traumatic Brain Injury were invited to participate in the study. Participants underwent clinical gait analysis and were grouped depending on the presence or absence of focal muscle spasticity. Kinetic data was obtained for each sub-group, and participants were compared to healthy controls. FINDINGS: Hip extensor power generation at initial contact, hip flexor power generation at terminal stance, and knee extensor power absorption at terminal stance were all significantly increased, and ankle power generation was significantly reduced at push-off when comparing Traumatic Brain Injury to healthy control populations. There were only two significant differences between participants with and without focal muscle spasticity, hip extensor power generation at initial contact was increased (1.53 vs 1.03 W/kg, P < .05) for those with focal hamstring spasticity, and knee extensor power absorption in early stance was reduced (-0.28 vs -0.64 W/kg, P < .05) for those with focal rectus femoris spasticity. However, these results should be interpreted with caution as the sub-group of participants with focal hamstring and rectus femoris spasticity was small. INTERPRETATION: Focal muscle spasticity had little association with abnormal gait kinetics in this cohort of independently ambulant people with Traumatic Brain Injury.

Human femur morphology and histology variation with ancestry and behaviour in an ancient sample from Vietnam.

BACKGROUND: There is a genetic component to the minimum effective strain (MES)-a threshold which determines when bone will adapt to function-which suggests ancestry should play a role in bone (re)modelling. Further elucidating this is difficult in living human populations because of the high global genetic admixture. We examined femora from an anthropological skeletal assemblage (Mán Bac, Vietnam) representing distinct ancestral groups. We tested whether femur morphological and histological markers of modelling and remodelling differed between ancestries despite their similar lifestyles. METHODS: Static histomorphometry data collected from subperiosteal cortical bone of the femoral midshaft, and gross morphometric measures of femur robusticity, were studied in 17 individuals from the Mán Bac collection dated to 1906-1523 cal. BC. This assemblage represents agricultural migrants with affinity to East Asian groups, who integrated with the local hunter-gatherers with affinity to Australo-Papuan groups during the mid-Holocene. Femur robusticity and histology data were compared between groups of 'Migrant' (n = 8), 'Admixed' (n = 4), and 'Local' (n = 5). RESULTS: Local individuals had more robust femoral diaphyses with greater secondary osteon densities, and relatively large secondary osteon and Haversian canal parameters than the migrants. The Migrant group showed gracile femoral shafts with the least dense bone made up of small secondary osteons and Haversian canals. The Admixed individuals fell between the Migrant and Local categories in terms of their femoral data. However, we also found that measures of how densely bone is remodelled per unit area were in a tight range across all three ancestries. CONCLUSIONS: Bone modelling and remodelling markers varied with ancestral histories in our sample. This suggests that there is an ancestry related predisposition to bone optimising its metabolic expenditure likely in relation to the MES. Our results stress the need to incorporate population genetic history into hierarchical bone analyses. Understanding ancestry effects on bone morphology has implications for interpreting biomechanical loading history in past and modern human populations.

Female bone physiology resilience in a past Polynesian Outlier community.

Remodelling is a fundamental biological process involved in the maintenance of bone physiology and function. We know that a range of health and lifestyle factors can impact this process in living and past societies, but there is a notable gap in bone remodelling data for populations from the Pacific Islands. We conducted the first examination of femoral cortical histology in 69 individuals from ca. 440-150 BP Taumako in Solomon Islands, a remote 'Polynesian Outlier' island in Melanesia. We tested whether bone remodelling indicators differed between age groups, and biological sex validated using ancient DNA. Bone vascular canal and osteon size, vascular porosity, and localised osteon densities, corrected by femoral robusticity indices were examined. Females had statistically significantly higher vascular porosities when compared to males, but osteon densities and ratios of canal-osteon (~ 8%) did not differ between the sexes. Our results indicate that, compared to males, localised femoral bone tissue of the Taumako females did not drastically decline with age, contrary to what is often observed in modern populations. However, our results match findings in other archaeological samples-a testament to past female bone physiology resilience, also now observed in the Pacific region.

Lateral Centre of Mass Displacement can predict running in adults with traumatic brain injury.

BACKGROUND: Running is an important skill that improves a person's ability to participate in community-based social, leisure and work activities, and therefore improve quality of life. Following traumatic brain injury, many ambulant people are unable to run. Whilst established for walking, the physical impairments that limit running following traumatic brain injury remain unknown. Therefore, the primary aim of this study was to identify which physical impairments contribute to a person's ability to run post traumatic brain injury. METHODS: In this study, 88 adults with traumatic brain injury were included. Runners and non-runners were compared regarding their clinical assessment of physical impairments, including postural control, focal muscle spasticity, muscle strength, self-selected walking speed and ability to run. Participants also completed a three-dimensional quantitative gait analysis to assess motor skill using the Gait Profile Score. Logistic regression was applied to identify the most important predictors for the ability to run. FINDINGS: Significant differences between runners and non-runners were found for postural control, motor control and strength. Dynamic postural control, measured by lateral center of mass displacement, was the best predictor of running, with every centimeter increase in lateral center of mass movement during walking associated with a 30% reduction in the chance of being able to run. INTERPRETATION: Lateral center of mass displacement should be considered when selecting interventions for ambulant patients with the goal to run. Although postural control, motor control and muscle strength were all different between runners and non-runners, they did not contribute to a person's ability to run.

Forager and farmer evolutionary adaptations to malaria evidenced by 7000 years of thalassemia in Southeast Asia.

Thalassemias are inherited blood disorders that are found in high prevalences in the Mediterranean, Southeast Asia and the Pacific. These diseases provide varying levels of resistance to malaria and are proposed to have emerged as an adaptive response to malaria in these regions. The transition to agriculture in the Holocene has been suggested to have influenced the selection for thalassemia in the Mediterranean as land clearance for farming encouraged interaction between Anopheles mosquitos, the vectors for malaria, and human groups. Here we document macroscopic and microscopic skeletal evidence for the presence of thalassemia in both hunter-gatherer (Con Co Ngua) and early agricultural (Man Bac) populations in northern Vietnam. Firstly, our findings demonstrate that thalassemia emerged prior to the transition to agriculture in Mainland Southeast Asia, from at least the early seventh millennium BP, contradicting a long-held assumption that agriculture was the main driver for an increase in malaria in Southeast Asia. Secondly, we describe evidence for significant malarial burden in the region during early agriculture. We argue that the introduction of farming into the region was not the initial driver of the selection for thalassemia, as it may have been in other regions of the world.

Using Tree Rings to Track Atmospheric Mercury Pollution in Australia: The Legacy of Mining in Tasmania.

Historical records of mercury (Hg) deposition in lake sediments have commonly been used to monitor historic atmospheric concentrations. In the Australian environment, however, freshwater lakes are limited, restricting the region for which depositional archives of Hg can be derived. In this study we show that dendrochemistry can provide a record of atmospheric concentrations at very high resolution. We measured Hg concentrations in growth rings of two tree species from a site in western in Tasmania-Huon Pine ( Lagarostrobus franklinii) and Celery Top Pine ( Phyllocladus aspleniifolius). This region has been heavily mined over the past 150 years. Although much previous work has linked atmospheric Hg to gold mining, the evidence in this study suggests that copper smelters in Queenstown and Zeehan, not gold mining activities, were the main sources of Hg emissions to the atmosphere in this location. Huon Pine had significantly higher background Hg concentrations ( x̅ = 5.62 ng/g) than Celery Top Pine ( x̅ = 2.95 ng/g). No significant increase in Hg concentration during the peak copper smelting phase (1896 to 1935) was observed in Celery Top Pine, while a significant 1.4 fold-increase was observed in Huon Pine. Our results show that of species examined across the globe, Huon Pine is one of the most efficient bioaccumulators of Hg, making it a good proxy for tracking historical Hg emissions in western Tasmania. This ability to measure Hg in the environment is essential if Australia ratifies the Minamata Convention.