Development of a Prediction Model for Stress Fracture During an Intensive Physical Training Program:The Royal Marines Commandos

Background Stress fractures (SF) are one of the more severe overuse injuries in military training and therefore knowledge of potential risk factors is needed to assist in developing mitigating strategies. Purpose To develop a prediction model for risk of SF in Royal Marines (RM) recruits during an arduous military training program. Study Design Cohort study Methods 1,082 recruits (age range: 16-33 years) enrolled between September 2009 and July 2010, were prospectively followed through the 32-week RM training program. SF diagnosis was confirmed from a positive X-Ray or Magnetic Resonance Imaging (MRI) scan. Potential risk factors assessed at week-1 included recruit characteristics, anthropometric assessment, dietary supplement use, lifestyle habits, fitness assessment, blood samples, 25(OH)D, bone strength as measured by heel Broadband Ultrasound Attention (BUA), history of physical activity, and previous and current food intake. A logistic least absolute shrinkage selection operator (LASSO) regression with 10-fold cross-validation method was used to select potential predictors among 47 candidate variables. Model performance was assessed using measures of discrimination (c-index) and calibration. Bootstrapping was used for internal validation of the developed model and to quantify optimism. Results A total of 86 (8%) volunteer recruits presented with at least one SF during training. Twelve variables were identified as the most important risk factors of SF. Variables strongly associated with SF were age, body weight, pre-training weight bearing (WB) exercise, pre-training cycling and childhood intake of milk and milk products. The c-index for the prediction model was 0.73 (optimism-corrected c-index 0.68), which represents the model performance in future volunteers. Although 25(OH)D and VO2max had only a borderline statistical significant association with SF, the inclusion of these factors improved the performance of the model. Conclusion These findings will assist in identifying recruits at greater risk of SF during training, and support interventions to mitigate this injury risk. However, external validation of the model is still required.</p

Abrasive wear behaviour of conventional and large-particle tungsten carbide-based cermet coatings as a function of abrasive size and type

Abrasive wear behaviour of materials can be assessed using a wide variety of testing methods, and the relative performance of materials will tend to depend upon the testing procedure employed. In this work, two cermet type coatings have been examined, namely (i) a conventional tungsten carbide-cobalt thermally sprayed coating with a carbide size of between ∼0.3 – 5 μm and (ii) a tungsten carbide-nickel alloy weld overlay with large spherical carbides of the order of ∼50 – 140 μm in diameter (DuraStell). The wear behaviour of these two materials has been examined by the use of two abrasion tests, namely the micro-scale abrasion test using both silica and alumina abrasives (typically 2-10 μm in size), and the dry sand-rubber wheel test (ASTM G65), again with both silica and alumina abrasives (typically 180 – 300 μm in size). It was found that when the abrasive particles were of the same scale or larger than the mean free path between the hard phase particles, then the matrix phase was well protected by the hard phases. Testing (in both test types) with alumina abrasives resulted in wear of both the hard carbide phases and the matrix phases in both the thermally sprayed coating and the weld overlay, with the thermally sprayed coating exhibiting lower wear rates. The wear behaviour of the materials with the more industrially relevant silica abrasive was more complex; the thermally sprayed coating exhibited a lower wear rate than the weld overlay with the fine abrasive in the micro-scale abrasion test due to effective shielding of the matrix from abrasive action due to the fine reinforcement particle size. In contrast, with the coarser silica abrasive in the dry sand-rubber wheel test, the weld overlay with the large carbides was able to provide matrix protection with low rates of wear, whereas the thermally sprayed coating wore by fracture of the more brittle microstructure. These findings demonstrate the importance of selection of appropriate laboratory test procedures and abrasives to simulate behaviour of materials in service environments

The effects of dietary sodium intake on heat acclimation and thermoregulation during heat exposure

SIGLEAvailable from British Library Document Supply Centre-DSC:DXN016755 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

The effect of sodium balance on sweat sodium secretion and plasma aldosterone concentration

The effect of manipulating sodium intake upon sweat sodium secretion was investigated during heat acclimation. Twenty-five male subjects were confined to an environmental chamber at a temperature of 25 degrees C for 3 days, and then acclimated to heat by a further 5 days at 40 degrees C. The subjects' daily sodium intake was controlled throughout as follows: high (HNa), 348.4 (0.8) mmol x day(-1), n=7; moderate (MNa), 174.1 (0.6) mmol x day(-1), n=9; or low (LNa), 66.3 mmol x day(-1), n=9. Sodium losses were estimated from urinary, faecal and sweat collections using a whole-body washdown method. Plasma aldosterone concentration was also measured from venous blood sampled each morning. Measurements of body temperature and heart rate during the heat exposure phase indicated a degree of heat acclimation. During this heat phase there was a reduction (P &lt; 0.01) in sweat sodium secretion for all three conditions which was greatest for the LNa condition, although this finding was not significant (P &lt; 0.1). In the LNa condition, plasma aldosterone concentration increased (P &lt; 0.05) prior to heat exposure, and the secretion of aldosterone was potentiated (P &lt; 0.01) during the heat exposure in comparison with the MNa condition. In contrast, the HNa diet produced a fall (P &lt; 0.05) in plasma aldosterone concentration prior to heat exposure and an attenuation of aldosterone secretion thereafter. These findings are inconsistent with the hypothesis that retention of sweat sodium is dependent upon a net body sodium deficit, but demonstrate that aldosterone secretion is potentiated under such conditions

Equid herpesviruses 1 and 4 encode functional homologs of the herpes simplex virus type 1 virion transactivator protein, VP16

The herpes simplex virus type 1 (HSV-1) tegument protein VP16 is a potent transcriptional inducer of immediate-early gene expression, comprising an N-terminal domain involved in binding DNA linked to an acidic transactivating C-terminal domain. The gene encoding the counterpart of this protein in equid herpesvirus 4 (EHV-4) was sequenced. Comparisons with VP16 and the homologous proteins of equine herpesvirus 1 (EHV-1) and varicella-zoster virus (VZV) showed that a region in the N-terminal domain involved in formation of a complex with cellular proteins is partially conserved in all four proteins. In contrast, the C terminal regions of the EHV proteins, like that of VZV, are not particularly acidic and are not significantly conserved with respect to the C-terminal region of VP16. Nevertheless, transient expression experiments indicated that the EHV-1 and EHV-4 proteins are able to transactivate HSV-1 and EHV-1 immediate-early promoters in a dose-dependent manner, which suggests that this activity is not dependent on an acidic C-terminal domain

Sequence analysis of HLA-Bw53, a common West African allele, suggests an origin by gene conversion of HLA-B35

In the West African population of the Gambia the class I antigen HLA-Bw53 is found at high frequency. We used the polymerase chain reaction to amplify cDNA from an individual homozygous for this allele and determined the nucleotide sequence of the polymorphic α1 and α2 domains. The HLA-Bw53 sequence is identical to HLA-B35 except for a short sequence at the 3′ end of exon 2 (encoding the α1 domain) which specifies a Bw4 rather than a Bw6 motif. This suggests an origin for HLA-Bw53 involving a gene conversion of HLA-B35 by an allele containing this Bw4 sequence. The α2 domain shared by HLA-Bw53, -B35, and -Bw58 is particularly common in sub-Saharan Africans