Christopher Garry Irwin

Griffith University · School of Allied Health Sciences

The aim of this study was to systematically review prior research investigating the effects of contact/collision sport participation on neurometabolite levels in the absence of concussion. Four online databases were searched to identify studies that measured neurometabolite levels in contact/collision sport athletes (without concussion) using proto...

Infant sleep problems have been associated with a myriad of adverse child and parent outcomes, yet whether these problems may pose a risk for parents on the road has received little research attention. This study sought to test whether mothers of infants with insomnia are at an elevated risk for vehicular crashes, by comparing their objectively mea...

Introduction Sleep quality and quantity is impacted by age, with women more susceptible to these age-related changes. Poor sleep in older adults is linked to adverse health outcomes and a greater risk of all-cause mortality. Given the ageing population in Australia, strategies to improve sleep in older adults is critical. Diet is a modifiable lifes...

Issues Young adults (aged 18–24 years) are more likely to binge drink than any other age group in Australia. These behaviours expose young adults to possible adverse events, with potential for acute harms. Approach A behavioural framework (capability, opportunity, motivation—behaviour [COM‐B model]) was used to explore factors that influence the d...

Objective This study examined adherence to dietary guidelines and symptoms of sleep problems (e.g., taking a long time to fall sleep or waking up early) and their associations in a sample of older Australian women (68-73 years of age). Design This was a population-based cross-sectional study. Adherence to the dietary guidelines was measured using...

Issue addressed: Early childhood education and care (ECEC) settings are ideal environments to optimise nutrition and positively influence children's food behaviours. However, recent research has identified the need to improve nutrition policies, food provision, and mealtime environments in Australian ECEC settings. This study explored the percepti...

Objectives: Low-alcohol beverages (LABs) are becoming increasingly popular and more accepted in Australia. However, the extent to which these products are accessible in licensed venues remains unknown. This investigation aimed to explore the availability, visibility, advertising, and promotion of LAB products at licensed venues. Study type: A cros...

Objective: Diet-related apps and websites are developed to help improve dietary intake. The aim of this study is to explore the use and acceptability of diet-related apps and websites in Australia. Methods: In a cross-sectional study, 241 participants (mean age = 40.6 years) completed an online survey about demographic characteristics, lifestyle...

Background Cannabidiol (CBD) has demonstrated anti-inflammatory, analgesic, anxiolytic and neuroprotective effects that have the potential to benefit athletes. This pilot study investigated the effects of acute, oral CBD treatment on physiological and psychological responses to aerobic exercise to determine its practical utility within the sporting...

Coaches are important figures of influence with potential to create environments that influence athlete health and performance outcomes. Ideally, coaches provide supportive environments that lead to performance optimisation and long-term health. Coaches who employ language and behaviours that overemphasise body composition and/or provide misinforme...

Introduction There is a clear need for novel interventions for insomnia disorder. Growing evidence suggests a role of the endogenous cannabinoid system in regulating circadian sleep-wake cycles, highlighting a potential avenue for novel therapeutics. Cannabinol (CBN), a trace cannabinoid formed through oxidation of delta-9-tetrahydrocannbinol (THC)...

In this study we investigated the effects of variously derived sources of low-dose caffeine on mood/arousal and cognitive performance. Twenty-two participants (15 men, 7 women; M age: 28.2, SD = 9.0 years) undertook five randomized, crossover trials in which they consumed either a water control (CON) or 80 mg of caffeine from one of four sources (c...

Bioelectrical impedance analysis (BIA) is an objective hydration and body composition assessment method recommended for use in haemodialysis patients. Limited research exists on the acceptability and utility of BIA in clinical practice. This qualitative study explored patient and staff acceptability and perceived value of BIA in an outpatient haemo...

Background Sleep loss may influence subsequent physical performance. Quantifying the impact of sleep loss on physical performance is critical for individuals involved in athletic pursuits. Design Systematic review and meta-analysis. Search and Inclusion Studies were identified via the Web of Science, Scopus, and PsycINFO online databases. Investi...

Background Cannabidiol (CBD), a major cannabinoid of Cannabis sativa, is widely consumed in prescription and non-prescription products. While CBD is generally considered ‘non-intoxicating’, its effects on safety-sensitive tasks are still under scrutiny. Aim We investigated the effects of CBD on driving performance. Methods Healthy adults ( n = 17...

BACKGROUND Poor diet is a contributing factor to the risk and burden of noncommunicable diseases. Diet apps and websites are developed to help improve dietary intake. OBJECTIVE The aim of this study is to explore the use and acceptability of diet apps and associated websites in Australia. METHODS In a cross-sectional study, 241 participants (mean...

Cardiovascular disease (CVD) poses a serious health and economic burden worldwide. Modifiable lifestyle factors are a focus of research into reducing the burden of CVD, with diet as one of the most investigated factors. Specifically, the timing and regularity of food intake is an emerging research area, with approaches such as time-restricted eatin...

Context Prolonged high salt (sodium) intake can increase the risk of hypertension and cardiovascular disease. Behavioral interventions may help reduce sodium intake at the population level. Objective The effectiveness of behavior change interventions to reduce sodium intake in adults was investigated in this systematic review and meta-analysis. D...

Blood and oral fluid Δ⁹-tetrahydrocannabinol (THC) concentrations are often used to identify cannabis-impaired drivers. We used meta-analytic techniques to characterise the relationships between biomarkers of cannabis use, subjective intoxication, and impairment of driving and driving-related cognitive skills. Twenty-eight publications and 822 driv...

Older adults experience reduced sleep quality and quantity more frequently than younger adults. Inadequate sleep in older adults has been linked to several adverse outcomes such as poor psychological and physical health, cognitive impairments, increased risk of falls, lower quality of life, and greater risk of all-cause and cardiovascular mortality...

Purpose of Review Older adults more frequently experience reduced sleep quality and quantity compared to younger adults. Diet is one modifiable lifestyle factor that may influence sleep outcomes in older adults. The purpose of this review is to synthesise the current literature investigating the impact of diet, including foods and nutrients, on the...

Many jurisdictions use point‐of‐collection (POC) oral fluid testing devices to identify driving under the influence of cannabis, indexed by the presence of Δ9‐tetrahydrocannabinol (THC), an intoxicating cannabinoid, in oral fluid. While use of the non‐intoxicating cannabinoid, cannabidiol (CBD), is not prohibited among drivers, it is unclear whethe...

The aim of this study was to determine the influence of training volume alterations on diversity and composition of the gut microbiome in a free-living cohort of middle-distance runners. Fourteen highly-trained middle-distance runners (n=8 men; V˙O2peak = 70.1 ± 4.3 ml·kg·min⁻¹; n=6 women, V˙O2peak: 59.0 ± 3.2 ml·kg·min⁻¹) completed three weeks of...

This study examined the impact of varying the holding time following an ad libitum laboratory breakfast on acute dietary behaviour and subsequent intake. Twenty-four participants (20 females (age: 23.4 ± 6.3 years; body mass index: 23.9 ± 3.9 kg·m –2 , mean ± SD)) completed 3 trials following a quasi-randomised, crossover design. Each trial (7-day...

This study aimed to determine if belief in caffeine's ergogenic potential influences choice reaction time (CRT) and/or running performance. Twenty‐nine healthy individuals (23.7 ± 5 years, 16 males) completed two trials (one week apart). Before the trials, participants indicated their “belief” in caffeine's ergogenic effects and previous “experienc...

Aim: Nursing students experience high levels of stress, anxiety and depression. This study examined associations between health behaviors and stress, anxiety and depression in Australian nursing students. Design: this was a cross-sectional study. Methods: Participants completed an online survey providing demographic information and responses t...

Health‐related quality of life (HRQoL) is being increasingly studied as an indicator of wellbeing. This study evaluated the HRQoL of nursing students and relationships between lifestyle behaviours including smoking, diet, alcohol intake and physical activity. A cross‐sectional study was conducted in 2018 using the Short Form 12V2 to measure the HRQ...

Developmental vulnerability in children often impacts social, educational, and health outcomes that then determine a child’s developmental trajectory into adolescence and adulthood. It is widely accepted that early detection of vulnerability and implementation of targeted educational support can optimise children’s outcomes, particularly when imple...

The aim of this scoping review was to describe the extent to which RED-S education is incorporated into the coach accreditation pathways of endurance sporting organizations. Five national sporting organizations (Cycling Australia, Athletics Australia, Swimming Australia, Triathlon Australia, and Rowing Australia) were contacted to participate. Firs...

Aim: University students often cite increased monetary cost as a major barrier to improved eating behaviours. Here, we examine food expenditure behaviours in a sample of Australian university students. Methods: Students (n = 147) collected and analysed a 24-hour food record to determine their food group and nutrient intakes, then costed the food...

Background Rapid restoration of muscle glycogen stores is imperative for athletes undertaking consecutive strenuous exercise sessions with limited recovery time (e.g. ≤ 8 h). Strategies to optimise muscle glycogen re-synthesis in this situation are essential. This two-part systematic review and meta-analysis investigated the effect of consuming car...

The increasing legal availability of cannabis has important implications for road safety. This systematic review characterised the acute effects of Δ⁹-THC on driving performance and driving-related cognitive skills, with a particular focus on the duration of Δ⁹-THC-induced impairment. Eighty publications and 1534 outcomes were reviewed. Several mea...

It is the position of Sports Dietitians Australia (SDA) that exercise in hot and/or humid environments, or with significant clothing and/or equipment that prevents body heat loss (i.e., exertional heat stress), provides significant challenges to an athlete’s nutritional status, health, and performance. Exertional heat stress, especially when prolon...

Objective Research into cognitive performance during a hangover has produced equivocal findings. This study investigated the reliability of inducing hangover symptoms and effects on cognitive performance (including applied tasks) under standardised conditions. Method Twenty‐one participants (13 M; 24 ± 3 years) completed two identical trials, invo...

The cognitive effects of acute aerobic exercise were investigated in endurance-trained individuals. On two occasions, 21 cyclists; 11 male (VO2max: 57 ± 9 mL·kg⁻¹·min⁻¹) and 10 female (VO2max: 51 ± 9 mL·kg⁻¹·min⁻¹), completed 45 min of fixed, moderate-intensity (discontinuous) cycling followed by an incremental ride to exhaustion. Cognitive functio...

The aim of this study was to identify markers of training stress and characteristics of middle-distance runners related to the incidence of overreaching following overload training. Twenty-four highly-trained runners (n=16 male; VO 2peak =73.3(4.3) mL·kg·min ⁻¹ ; n=8 female, VO 2peak =63.2(3.4) mL·kg·min ⁻¹ ) completed 3 weeks of normal training (N...

Background Nursing students are at risk of inadequate sleep and poor lifestyle behaviours due to academic, clinical and personal stressors faced throughout their training. However, the relationship between lifestyle and sleep in this population is not well understood. Aim The aim of this study was to determine whether inadequate sleep was associat...

Objective Interest in the use of cannabidiol (CBD) is increasing worldwide as its therapeutic effects are established and legal restrictions moderated. Unlike Δ⁹‐tetrahydrocannabinol (Δ⁹‐THC), CBD does not appear to cause cognitive or psychomotor impairment. However, further assessment of its effects on cognitively demanding day‐to‐day activities,...

Cannabidiol (CBD) is a non-intoxicating cannabinoid derived from Cannabis sativa. CBD initially drew scientific interest due to its anticonvulsant properties but increasing evidence of other therapeutic effects has attracted the attention of additional clinical and non-clinical populations, including athletes. Unlike the intoxicating cannabinoid, Δ...

Smoothies are a popular breakfast option. However, liquids may evoke weaker satiation than nutritionally comparable semi-solid and solid foods. This study examined consumption of cereal and milk (CM) or a nutritionally comparable fruit smoothie (FS) for breakfast on subsequent dietary behaviours, in a controlled laboratory setting. Twenty-five part...

Introduction Insomnia is a highly prevalent and costly condition that is associated with increased health risks and healthcare utilisation. Anecdotally, cannabis use is frequently reported by consumers to promote sleep. However, there is limited research on the effects of cannabis on sleep and daytime function in people with insomnia disorder using...

Inadequate sleep (i.e., duration and/or quality) is becoming increasingly recognized as a global public health issue. Interaction via the gut-brain axis suggests that modification of the gut microbial environment via supplementation with live microorganisms (probiotics) or nonviable microorganisms/microbial cell fractions (paraprobiotics) may impro...

Caffeinated products are often consumed as a popular countermeasure to the effects of sleep loss. However, the efficacy of caffeine to exert these effects after consecutive nights of sleep loss is poorly understood. The aim of this study was to investigate the effects of three consecutive nights of restricted sleep and morning caffeine consumption...

Many processes are involved in sleep regulation, including the ingestion of nutrients, suggesting a link between diet and sleep. Aside from studies investigating the effects of tryptophan, previous research on sleep and diet has primarily focused on the effects of sleep deprivation or sleep restriction on diet. Furthermore, previous reviews have in...

In the last decade, there has been greater appreciation of the harmful consequences of Relative Energy Deficiency in Sport (RED-S), particularly in adolescent female athletes. Coaches act as both important moderators in the development of the condition and as identifiers of athletes at risk. Research suggests that coaches lack knowledge on this top...

This study investigated the effect of acute aerobic exercise, dehydration and fluid intake on choice reaction time (CRT) and the ex-Gaussian CRT distribution. On 4 separate occasions, 8 trained females (body mass [BM]: 61.8±10.7 kg; VO 2 max : 46.3±7.5 mL·kg-1 ·min-1) lost 2.0±0.3% BM cycling at ~75% VO 2max (~60 min, 24.2±0.9°C) before commencing...

Caffeine is widely used to counteract the effects of sleep loss. This systematic review and meta-analysis examined the impact of acute caffeine consumption on cognitive, physical, occupational and driving performance in sleep deprived/restricted individuals. 45 publications providing 327 effect estimates (EEs) were included in the review. Caffeine...

This study investigated the effect of drinking rate on fluid retention of milk and water following exercise-induced dehydration. In Part A, 12 male participants lost 1.9% ± 0.3% body mass through cycle exercise on four occasions. Following exercise, plain water or low-fat milk equal to the volume of sweat lost during exercise was provided. Beverage...

Objective: Fatal vision goggles (FVGs) are image-distorting equipment used to simulate alcohol impairment in driver education programs. Unlike alcohol, which disrupts cognitive processes, FVG only induces visual impairment. Performing concurrent cognitive tasks while wearing FVG may reduce the wearer’s attentional resources and provide a better sim...

Background The main psychoactive component of cannabis, delta-9-tetrahydrocannabinol (THC), can impair driving performance. Cannabidiol (CBD), a non-intoxicating cannabis component, is thought to mitigate certain adverse effects of THC. It is possible then that cannabis containing equivalent CBD and THC will differentially affect driving and cognit...

Lack of time, financial issues, and stressful clinical and educational environments in nursing studies promote higher intakes of convenience and fast foods loaded with fat and sugar, which are linked to reduced mental and physical health. In this study, we examined the dietary patterns of nursing students and their associated sociodemographic facto...

Motor racing is a physically and mentally demanding sport, associated with a high degree of risk for drivers. Hence, driving simulation provides a safe alternative to explore the impact acute physiological perturbations (e.g. heat stress or dehydration) on a driver's performance. This study aimed to determine sensitive and reliable simulated drivin...

Motor-racing drivers are often exposed to hot environments and may be susceptible to fluid loss and hydration issues, which could influence driving performance. This study assessed the effect of dehydration and heat stress on performance during a short, simulated motor-racing task. Nine healthy males (age: 26.6 ± 7.5 y, body mass: 78.8 ± 12.5 kg, m...

Objectives: Skin tattoos have been shown to reduce localised sweat rate and increase sweat sodium concentration ([Na+]) when sweating is artificially stimulated. This study investigated whether similar responses are observed with exercise-induced sweating. Design: Unblinded, within-participant control, single trial. Methods: Twenty-two healthy...

This study assessed voluntary dietary intake when different beverages were provided within a recovery area following recreational exercise. Participants completed two 10-km runs 1 week apart. Immediately after the first run, "beer drinkers" (n = 54; mean ± SD: age = 23.9 ± 5.8 years, body mass [BM] = 76 ± 13 kg) randomly received low-alcohol beer (...

Background: Food-based dietary guidelines are designed to support populations to adopt a healthy diet. University students studying nutrition related courses are typically en-route to professional roles that involve advocating a healthy diet. Aim: The present study compared the dietary intake of university students enrolled in a foundation nutri...

Smoothies are popular breakfast foods. This study examined the effect of consuming Cereal & Milk (CM) or a nutritionally-comparable Fruit Smoothie (FS) for breakfast on daily energy intake (EI) in free-living adults and the extent to which individuals compensated for calories ingested in a High Energy Fruit Smoothie (HE). Ten participants (28.4 ± 2...

This study investigated the effect of consuming either water or a carbohydrate (CHO)-electrolyte sports beverage (‘Sports Drink’) ad libitum with food during a 4 h post-exercise recovery period on fluid restoration, nutrient provision and subsequent endurance cycling performance. On two occasions, 16 endurance-trained cyclists; 8 male [M] (age: 31...

Caffeine content of Nespresso Pod. Video summary available (.avi) - play via VLC media player or similar

Background:: Little independent information on the caffeine content of the popular Nespresso® coffee pod range exists. Aim:: To quantify the caffeine content of Nespresso® pod coffees. Methods:: Initially, three serves (ristretto (S), espresso (M), lungo (L)) of two pod varieties (Livanto and Roma) were prepared on three different Nespresso® m...

Purpose: The gut-liver interaction suggests that modification of gut bacterial flora using probiotics and synbiotics may improve liver function. This systematic review and meta-analysis aimed to clarify the effect of probiotics and synbiotics consumption on the serum concentration of liver function enzymes. Methods: PubMed (MEDLINE), Cumulative...

Encapsulated (Pod) coffee is increasingly popular and available in a range of flavor and intensity profiles. This study examined consumption of different coffee Pods on mood and cognitive performance. Thirty-eight participants (n=6 males, 32 females; age: 23.9±5.4 years; weight: 64.3±11.9 kg; BMI: 22.4±2.7 kg·m⁻²; mean±SD) completed 3 trials, consu...

Smoothies are popular dietary products. An online survey of Australian adults (n=833; 79% female) was used to explore patterns of smoothie consumption and individual motives for consuming these beverages. Participants commonly reported consuming fruit (98%), yoghurt (66%), milk (58%), honey (52%), fruit juice (46%), and nutritional supplements (46%...

Purpose: This study investigated the effect of consuming different commercial beverages with food ad libitum post-exercise on fluid, energy and nutrient recovery in trained females. Methods: On 4 separate occasions, 8 females (body mass [BM]: 61.8±10.7 kg; VO2max: 46.3±7.5 mL·kg-1·min-1) lost 2.0±0.3% BM cycling at ~75%VO2max before completing a...

Purpose: Modulating gut bacteria via regular prebiotics/probiotics consumption may improve the metabolism of acute alcohol ingestion. This study investigated the impact of 8-weeks prebiotics/probiotics supplementation on microbiome changes and responses to acute alcohol consumption. Methods: 38 participants (21 females, 23.6 ± 3.4 kg m-2, mean ±...