Objectives Military personnel are required to train and operate in challenging multi-stressor environments, which can affect hormonal levels, and subsequently compromise performance and recovery. The aims of this project were to 1) assess the impact of an eight-day military training exercise on salivary cortisol and testosterone, 2) track the recovery of these hormones during a period of reduced training. Methods This was a prospective study whereby 30 soldiers (n = 27 men, n = 3 women) undergoing the Australian Army combat engineer ‘Initial Employment Training’ course were recruited and tracked over a 16-day study period which included an eight-day military training exercise. Non-stimulated saliva samples were collected at waking, 30 min post waking, and bedtime on days 1, 5, 9, 13, 15; measures of subjective load were collected on the same days. Sleep was measured continuously via actigraphy, across four sequential study periods; 1) baseline (PRE: days 1–4), 2) field training with total sleep deprivation (EX-FIELD: days 5–8), 3) training at simulated base camp with sleep restriction (EX-BASE: days 9–12), and 4) a three-day recovery period (REC: days 13–15). Results Morning cortisol concentrations were lower following EX-FIELD (p<0.05) compared to the end of REC. Training in the field diminished testosterone concentrations (p<0.05), but levels recovered within four days. Bedtime testosterone/cortisol ratios decreased following EX-FIELD and did not return to pre-training levels. Conclusions The sensitivity of testosterone levels and the testosterone/cortisol ratio to the period of field training suggests they may be useful indicators of a soldier’s state of physiological strain, or capacity, however inter-individual differences in response to a multi-stressor environment need to be considered.

IntroductionMilitary personnel train and operate in challenging multistressor environments, which can affect hormonal levels, and subsequently compromise performance and recovery. The aims of this project were to evaluate concentrations of cortisol and testosterone and subjective perceptions of stress and recovery across basic military training (BMT).Methods32 male recruits undergoing BMT were tracked over a 12-week course. Saliva samples were collected weekly, on waking, 30 min postwaking and bedtime. Perceptions of stress and recovery were collected weekly. Daily physical activity (steps) were measured via wrist-mounted accelerometers across BMT. Physical fitness was assessed via the multistage fitness test and push-ups in weeks 2 and 8.ResultsConcentrations of testosterone and cortisol, and the testosterone:cortisol ratio changed significantly across BMT, with variations in responses concurrent with programmatic demands. Perceptions of stress and recovery also fluctuated according to training elements. Recruits averaged 17 027 steps per day between weeks 2 and 12, with week-to-week variations. On average, recruits significantly increased predicted VO2max(3.6 (95% CI 1.0 to 6.1) mL/kg/min) and push-ups (5. 5 (95% CI 1.4 to 9.7) repetitions) between weeks 2 and 8.ConclusionsRecruit stress responses oscillated over BMT in line with programmatic demands indicating that BMT was, at a group level, well-tolerated with no signs of enduring physiological strain or overtraining. The sensitivity of cortisol, testosterone and the testosterone:cortisol ratio to the stressors of military training, suggest they may have a role in monitoring physiological strain in military personnel. Subjective measures may also have utility within a monitoring framework to help ensure adaptive, rather than maladaptive (eg, injury, attrition), outcomes in military recruits.

The zinc finger transcription factor EGR4 has previously been identified as having a critical role in the proliferation of small cell lung cancer. Here, we have identified a novel, shortened splice variant of this transcription factor (EGR4-S) that is regulated by Heat Shock Factor-1 (HSF1). Our findings demonstrate that the shortened variant (EGR4-S) is upregulated with high EGFR, HER2, and H-Rasv12-expressing breast cell lines, and its expression is inhibited in response to HER pathway inhibitors. Protein and mRNA analyses of HER2+ human breast tumours indicated the novel EGR4-S splice variant to be preferentially expressed in tumour tissue and not detectable in patient-matched normal tissue. Knockdown of EGR4-S in the HER2-amplified breast cancer cell line SKBR3 reduced cell growth, suggesting that EGR4-S supports the growth of HER2+ tumour cells. In addition to chemical inhibitors of the HER2 pathway, EGR4-S expression was also found to be suppressed by chemical stressors and the overexpression of HSF1. Under these conditions, reduced EGR4-S levels were associated with the observed lower cell growth rate, but the augmentation of properties associated with higher metastatic potential. Taken together, these findings identify EGR4-S as a potential biomarker for HER2 pathway activation in human tumours that is regulated by HSF1.