Matthew J. McAllister’s research while affiliated with Texas State University and other places

Objective The present study examined novel and classic CVD risk factors among career firefighters to understand better the associations between physiological stress, oxidative stress, inflammation biomarkers, and CVD risk. Methods Associations between muscular and cardiorespiratory fitness (CRF) measures, body composition, physiological stress, and novel/classic CVD risk factors were assessed among 97 career male firefighters. Results Muscular fitness/CRF, adiposity, body composition, and blood lipids were associated with CVD risk as measured by biomarkers for insulin resistance, inflammation, and oxidative stress. No associations between physiological stress biomarkers and CVD risk factors were found. Conclusions Firefighters should improve their muscular fitness/CRF and body composition to reduce CVD risk.

Objective Law enforcement officers (LEOs) face numerous stressors that exacerbate cardiometabolic disease (CMD) risk. The current study examined novel and classic risk factors among a cohort of LEOs to better understand relationships between biomarkers of stress, oxidative stress, inflammation, and CMD risk. Methods Associations between measures of cardiorespiratory and muscular fitness, body composition, and cardiometabolic health with novel/classic CMD risk factors were assessed among 66 male LEOs. Results Muscular fitness and cardiorespiratory fitness were significantly associated with reduced insulin resistance. Moreover, higher fat mass and body fat percentages were significantly associated with increased markers of inflammation and insulin resistance. Conclusions Maintaining high cardiorespiratory and muscular fitness levels and improving body composition profiles can ameliorate cardiometabolic health.

Previous reports suggest that the menstrual cycle (MC) phases can impact cortisol concentrations. However, research is needed on whether the MC impacts other markers of stress and immune function. It has also been shown that some biomarkers are impacted by time of day, although differences between morning (AM) and afternoon (PM) biomarkers have not been studied over the course of the MC. This study assessed the effect of MC phases and time of day on salivary stress biomarkers [salivary α-amylase (sAA), secretory immunoglobulin A (SIgA)], progesterone, resting blood pressure and resting heart rate (RHR). A single-group repeated measure design was employed in which seventeen participants (n = 17) monitored their MC for two months while attending eight experimental sessions which included both AM and PM sessions during each predicted 1) menses, 2) follicular, 3) ovulatory and 4) luteal phases. Resting blood pressures, heart rates, body composition parameters (assessed via bioelectrical impedance analysis), sAA and SIgA concentrations were assessed. No time of day x MC phase interactions (p > 0.05) were noted for sAA or SIgA, resting blood pressure, heart rate, or body composition parameters. However, sAA and RHR were significantly higher in the PM, while SIgA was significantly higher in the AM. These data suggest that the MC phases do not impact sAA or SIgA, resting blood pressure, heart rates, or body composition parameters. However, time-of-day impacts RHR and concentrations of sAA and SIgA. These findings provide implications for female participants in research dealing with these biomarkers.

Ingestion of L-theanine and L-tyrosine has been shown to reduce salivary stress biomarkers and improve aspects of cognitive performance in response to stress. However, there have been no studies to concurrently examine the impact of both L-theanine and L-tyrosine ingestion during a mental stress challenge (MSC) involving a brief cognitive challenge and a virtual reality based active shooter training drill. Thus, the purpose of this study was to determine the impact of ingestion of L-theanine and L-tyrosine on markers of stress and cognitive performance in response to a virtual reality active shooter drill and cognitive challenge. The cognitive challenge involved a Stroop challenge and mental arithmetic. Eighty subjects (age = 21 ± 2.6 yrs; male = 46; female = 34) were randomly assigned L-tyrosine (n = 28; 2000 mg), L-theanine (n = 25; 200 mg), or placebo (n = 27) prior to MSC exposure. Saliva samples, state-anxiety inventory (SAI) scales, and heart rate (HR) were collected before and after exposure to the MSC. Saliva was analyzed for stress markers α-amylase (sAA) and secretory immunoglobulin A (SIgA). The MSC resulted in significant increases in sAA, SIgA, HR, and SAI. Ingestion of L-theanine and L-tyrosine did not impact markers of stress. However, the L-tyrosine treatment demonstrated significantly lower missed responses compared to the placebo treatment group during the Stroop challenge. These data demonstrate that ingestion of L-theanine or L-tyrosine does not impact markers of stress in response to a MSC but may impact cognitive performance. This study was pre-registered as a clinical trial ("Impact of supplements on stress markers”: NCT05592561).