Heat exposure as a cause of injury and illness in mine industry workers.

The objective of this study was to explore the association between ambient temperature and injuries and illnesses experienced by mine industry workers. Eleven years of de-identified data from a mine industry company in Australia was explored in regards to injuries and illnesses occurring due to outdoor exposure. Each case was filtered for reported symptoms, and meteorological data to match the location of the mine site and date reported were sourced. Of the 18 931 injuries and illnesses observed over the 11-year period, 151 cases of heat-related illness due to outdoor exposure were reported. Twenty-five conditions/symptoms of heat-illness were found, with the most prevalent being dehydration (n = 81), followed by heat rash (n = 40), dizziness (n = 24), and headache (n = 23). The mean number of symptoms reported by each worker was 2 ± 1. There was a positive correlation between ambient temperature and injuries/illnesses (r2 = 0.89, P < 0.001), where, as temperature increased so did the number of reported heat-related illnesses. Underreporting of heat-related illness and injury in the mining industry is likely, which is a risk to the health and wellbeing of employees. Workers require industry specific training about the severity of heat stress and the associated prevention strategies.

A seasonal comparison of a 14-day swing on cognitive function and psycho-physiological responses in mine service workers.

This study assessed the effect of season on cognitive function and psycho-physiological responses during a 14-day swing in mine-service workers. Cognitive function, thermal sensation and comfort, rating of perceived exertion, fatigue, hydration, core temperature and heart rate were assessed throughout a shift, on three separate days over a swing. Working memory and processing efficiency did not differ between seasons (p > 0.05), however counting and recall latencies improved throughout the swing (p < 0.05). Participants reported greater fatigue post-shift compared to pre-shift (p < 0.05). Thermal sensation, thermal comfort, and hydration were significantly elevated in summer compared to winter (p < 0.05). Specifically, workers were significantly/minimally dehydrated in summer/winter (urinary specific gravity = 1.025 ± 0.007/1.018 ± 0.007). Although cognitive function and thermal strain were not impaired in summer compared to winter, it is essential to reinforce worker's knowledge regarding hydration requirements. Additional education and/or incorporating scheduled rest breaks for hydration should be considered to ensure the health and safety of mine workers.

Symptoms of heat illness and water consumption habits in mine industry workers over the summer months in Australia.

Mine industry workers (n=515) from various locations in Australia completed a questionnaire to assess the prevalence of symptoms associated with heat-related illness and water consumption habits during a summer season. Participants read from a pre-defined list and noted any heat-related symptoms that they had experienced. The most prevalent symptoms experienced were fatigue, headache, sweating, and dark coloured urine, with 77% of respondents reporting at least one symptom. Workers with shorter employment durations had higher rates of reporting multiple symptoms (rates ratios: 1.40-1.72). The most prevalent water consumption amounts over an 11-12 h shift were 2-4 L by 37.3% of total respondents, followed by 1-2 L by 36.5% of respondents. Employers should inform workers about the severe implications of heat-related illnesses, implement regular water breaks, and educate personnel about the importance of water intake. Providing employees with self-check methods of hydration status is recommended to increase awareness of their hydration status.

Seasonal influence on cognitive and psycho-physiological responses to a single 11-h day of work in outdoor mine industry workers.

This study investigated the seasonal effects that working outdoors had on various parameters in mining industry workers over the course of a work-shift. Workers (n = 27) were assessed in summer (33.3 ± 4.2°C, 38 ± 18% RH; n = 13, age = 46 ± 14 y, BMI = 29.1 ± 5.7 kg/m2) and winter (23.6 ± 5.1°C, 39 ± 20% RH; n = 14, age = 44 ± 12 y, BMI = 31.2 ± 4.1 kg/m2). Core temperature and heart-rate were measured continuously (analyzed at five time points), while perceptual measures, cognitive and manual dexterity performance were assessed at various times over an 11-h shift at the start of a 14-day swing. Hydration was assessed (urine specific gravity) pre- and post-shift. Working memory was impaired in summer compared to winter (-10%; p = 0.039), however did not change throughout the shift. Processing efficiency was significantly reduced at 12 pm (-12%; p = 0.005) and 5 pm (-21%; p < 0.001) compared to 9 am, irrespective of season (p > 0.05). Manual dexterity (dominant-hand) improved over the shift (+13%, p = 0.002), but was not different between seasons. Perceived fatigue had no main effect of season or shift. Core temperature, heart-rate, thermal sensation and rating of perceived exertion increased throughout the shift, with only core temperature and thermal sensation showing a seasonal effect (summer: +0.33°C, +18%, respectively; p < 0.002). Notably, 23% of workers in summer and 64% in winter started work significantly dehydrated, with 54% and 64% in summer and winter, respectively, finishing work with significant to serious dehydration. Impairment in working memory in summer combined with high levels of dehydration over the work-shift reinforces the need for workplace education on the importance of hydration and risk of occupation heat stress. Abbreviations: Core temperature: Tc; Fly-in fly-out: FIFO; Ratings of perceived exertion: RPE; Relative humidity: RH; Urinary specific gravity: USG; Wet bulb globe temperature: WBGT.

Comparing thermal strain in outdoor maintenance and indoor service workers in the mining industry during summer.

While working in the heat is a common practice within the Australian mining industry, it can lead to adverse effects on cognitive function, productivity, and physical health. This study aimed to compare the thermal strain experienced by maintenance workers and service workers in the mining industry during summer. Psycho-physiological parameters, manual dexterity, and cognitive function were assessed in maintenance workers (n = 12) and service workers (n = 12) employed at mine site villages in north-west Australia. Maintenance workers had the freedom to self-select their work intensity and predominantly worked outdoors (33.9±4.2°C, 38±18% RH), whereas service workers had to work to a fixed schedule and worked intermittently indoors (∼64% of work shift; 29.5±3.4°C, 48±8% RH) and outdoors (∼36%; 35.4±4.6°C, 47±21% RH). All workers underwent assessment at the beginning (day 2/3), middle (day 7/8), and end of their swing (day 13/14), at various time points throughout their 11-12 h shift. Service workers completed more steps (11282±1794 vs. 7774±2821; p<0.001), experienced a higher heart rate (p = 0.049) and reported higher ratings of perceived exertion (p<0.001), thermal discomfort (p<0.001), thermal sensation (p<0.001), and fatigue (p<0.012) compared to maintenance workers. Urinary specific gravity values were higher (less hydrated) in service workers (1.024±0.007) compared to maintenance workers (1.018±0.006; p = 0.007), with USG being overall higher post- compared to pre-shift (1.022±0.008 vs. 1.020±0.006; p<0.05). Core temperature, working memory capacity, processing speed and manual dexterity did not differ between occupations. Workers in hot environments who cannot self-select their work intensity should be educated about the importance of hydration before, during, and after their work-shifts and provided with more scheduled rest breaks during their shift. Employers should closely monitor workers for symptoms of heat illness, discomfort, and fatigue to ensure the health and safety of the workers.

Impact of living and working in the heat on cognitive and psycho-physiological responses in outdoor fly-in fly-out tradesmen: a mining industry study.

Objective: This study aimed to evaluate complex cognitive function, manual dexterity and psycho-physiological parameters in tradesmen working outdoors in the mining industry during summer and winter. Methods: Twenty-six males working in a mining village in the north-west of Australia were assessed pre- and post-an 11-h shift at the start, middle, and end of a 14-day swing in summer (average daily temperature: 33.9°C, 38% RH; n = 12) and winter (24.3°C, 36% RH; n = 14). Results: Working memory performance did not differ between seasons, over the swing or shift (p ≥ 0.053). Processing efficiency and manual dexterity performance did not differ between seasons (p ≥ 0.243), yet improved over the course of the swing (p ≤ 0.001) and shift (p ≤ 0.001). Core temperature, heart rate, thermal comfort, rating of perceived exertion and thermal sensation were not significantly different between seasons (p ≥ 0.076); however, average shift dehydration was greater in winter compared to summer (1.021 ± 0.005 vs. 1.018 ± 0.006; p = 0.014). Conclusion: The ability to self-regulate the intensity of activity likely helped outdoor workers to thermoregulate effectively, minimising thermal strain during their swings and shifts, in turn explaining unaltered cognitive function and manual dexterity performance between seasons. Regardless of season, workers should receive education on dehydration and workplace risks to protect their health.

Higher operating theatre temperature during burn surgery increases physiological heat strain, subjective workload, and fatigue of surgical staff.

Raising the ambient temperature of the operating theatre is common practice during burn surgeries to maintain the patient's core body temperature; however, the effects of operating in the heat on cognitive performance, manual dexterity, and perceived workload of surgical staff have not been assessed in a real-world context. Therefore, the aim was to assess the real-time impact of heat during burn surgeries on staff's cognitive function, manual dexterity, and perceptual measures (workload, thermal sensation, thermal comfort, perceived exertion, and fatigue) and physiological parameters (core temperature, heart-rate, fluid loss, and dehydration). Ten burn surgery staff members were assessed in CON (24.0±1.1°C, 45±6% relative humidity [RH]) and HOT (30.8±1.6°C, 39±7% RH) burn surgeries (average 150 min duration). Cognitive performance, manual dexterity, and perceptual measures were recorded pre- and post-surgery, while physiological parameters were recorded throughout surgery. HOT conditions did not significantly affect manual dexterity or cognitive function (p > .05), however HOT resulted in heat strain (increased heart-rate, core temperature, and fluid loss: p < .05), and increased subjective workload, discomfort, perceived exertion, and fatigue compared to CON conditions (p < .05). Cognitive function and manual dexterity were maintained in hot conditions, suggesting that operating in approximately 31°C heat is a safe approach for patient treatment. However, job burnout, which is positively correlated with perceived workload, and the impact of cumulative fatigue on the mental health of surgery staff, must be considered in the context of supporting an effective health workforce.

Increased air temperature during repeated-sprint training in hypoxia amplifies changes in muscle oxygenation without decreasing cycling performance.

The present study aims to investigate the acute performance and physiological responses, with specific reference to muscle oxygenation, to ambient air temperature manipulation during repeated-sprint training in hypoxia (RSH). Thirteen male team-sport players completed one familiarisation and three experimental sessions at a simulated altitude of ∼3000 m (FIO2 0.144). Air temperatures utilised across the three experimental sessions were: 20°C, 35°C and 40°C (all 50% relative humidity). Participants performed 3 × 5 × 10-s maximal cycle sprints, with 20-s passive recovery between sprints, and 5 min active recovery between sets. There were no differences between conditions for cycling peak power, mean power, and total work (p>0.05). Peak core temperature (Tc) was not different between conditions (38.11 ± 0.36°C). Vastus lateralis muscle deoxygenation during exercise and reoxygenation during recovery was of greater magnitude in 35°C and 40°C than 20°C (p<0.001 for all). There was no condition × time interaction for Tc, skin temperature, pulse oxygen saturation, heart rate, rating of perceived exertion and thermal sensation (P>0.05). Exercise-induced increases in blood lactate concentration were higher in 35°C and 40°C than 20°C (p=0.010 and p=0.001, respectively). Integrating ambient temperatures up to 40°C into a typical RSH session had no detrimental effect on performance. Additionally, the augmented muscle oxygenation changes experienced during exercise and recovery in temperatures ≥35°C may indicate that the potency of RSH training is increased with additional heat. However, alterations to the training session may be required to generate a sufficient rise in Tc for heat training purposes.Highlights Heat exposure (35-40°C) did not affect mechanical performance during a typical RSH session. This indicates hot ambient temperature can be implemented during RSH, without negative consequence to training output.Hotter ambient conditions (35-40°C) likely result in greater muscle oxygenation changes during both exercise and recovery compared to temperate conditions.Although hotter sessions were perceived as more difficult and more thermally challenging, they did not further elevate Tc beyond that of temperate conditions. Accordingly, if intended to be used for heat acclimation purposes, alterations to the session may be required to increase heat load.

Repeated-sprint training in heat and hypoxia: Acute responses to manipulating exercise-to-rest ratio.

The aim of this study was to investigate acute performance and physiological responses to the manipulation of exercise-to-rest ratio (E:R) during repeated-sprint hypoxic training (RSH) in hot conditions. Twelve male team-sport players completed two experimental sessions at a simulated altitude of ∼3000 m (FIO2 0.144), air temperature of 40°C and relative humidity of 50%. Exercise involved either 3 × 5 × 10-s (E:R1:2) or 3 × 10 × 5-s (E:R1:4) maximal cycling sprints interspersed with active recoveries at 120W (20-s between sprints, 2.5 and 5-min between sets for E:R1:2 and E:R1:4 respectively). Sessions were matched for overall sprint and total session duration (47.5-min). Peak and mean power output, and total work were greater in E:R1:4 than E:R1:2 (p < 0.05). Peak core temperature was significantly higher in E:R1:4 than E:R1:2 (38.44 ± 0.33 vs. 38.20 ± 0.35°C, p = 0.028). Muscle deoxygenation magnitude during sprints was greater in E:R1:2 (28.2 ± 1.6 vs. 22.4 ± 4.6%, p < 0.001), while muscle reoxygenation did not differ between conditions (p > 0.05). These results indicate E:R1:4 increased mechanical power output and core temperature compared to E:R1:2. Both protocols had different effects on measures of muscle oxygenation, with E:R1:2 generating greater muscle oxygen extraction and E:R1:4 producing more muscle oxygenation flux, which are both important signals for peripheral adaptation. We conclude that the E:R manipulation during RSH in the heat might be used to target different physiological and performance outcomes, with these findings forming a strong base for future mechanistic investigation.Highlights During a typical repeated-sprint training session conducted in hot and hypoxic conditions, an exercise-to-rest ratio of 1:4 during sprint efforts displayed an increased mechanical power output compared to an exercise-to-rest ratio of 1:2. This represents a potentially useful increase in training stimulus.An exercise-to-rest ratio of 1:2 generated greater muscle oxygen extraction, while an exercise-to-rest ratio of 1:4 resulted in more muscle oxygenation flux and a higher core temperature, indicating key markers of environment-related physiological strain were varied between conditions.Exercise-to-rest ratio manipulation may be used to target different physiological and performance outcomes when prescribing repeated-sprint training in hot and hypoxic conditions.

Taking the plunge: When is best for hot water immersion to complement exercise in heat and hypoxia.

This investigation assessed the psycho-physiological and performance effects of hot water immersion (HWI) implemented either before or after a repeated-sprint training in hypoxia (RSH) session conducted in the heat. Ten participants completed three RSH trials (3 × 10 × 5-s sprints), conducted at 40°C and simulated altitude of 3000 m. A 30-min monitoring period preceded and followed all exercise sessions. In PRE, the pre-exercise period was HWI, and the post-exercise period was seated rest in temperate conditions. This combination was reversed in POST. In CON, participants were seated in temperate conditions for both periods. Compared to CON, PRE elicited a reduction in power output during each repeated-sprint set (14.8-16.2%, all p < 0.001), and a significantly higher core temperature (Tc) during the pre-exercise period and throughout the exercise session (p < 0.001 and p = 0.025, respectively). In POST, power output and Tc until the end of exercise were similar to CON, with Tc higher at the conclusion of the post-exercise period (p < 0.001). Time across the entire protocol spent ≥38.5°C Tc was significantly longer in PRE (48.1 ± 22.5 min) than POST (31.0 ± 11.3 min, p = 0.05) and CON (15.8 ± 16.3 min, p < 0.001). Employing HWI following RSH conducted in the heat provides effective outcomes regarding physiological strain and cycling performance when compared to pre-exercise or no HWI.

Heat Added to Repeated-Sprint Training in Hypoxia Does Not Affect Cycling Performance.

PURPOSE: This study aimed to assess the influence of graded air temperatures during repeated-sprint training in hypoxia (RSH) on performance and physiological responses. METHODS: Ten well-trained athletes completed one familiarization and 4 experimental sessions at a simulated altitude of 3000 m (0.144 FIO2) above sea level. Air temperatures utilized across the 4 experimental sessions were 20°C, 25°C, 30°C, and 35°C (all 50% relative humidity). The participants performed 3 sets of 5 × 10 seconds "all-out" cycle sprints, with 20 seconds of active recovery between sprints and 5 minutes of active recovery between sets (recovery intensity = 120 W). Core temperature, skin temperature, pulse oxygen saturation, heart rate, rating of perceived exertion, and thermal sensation were collected. RESULTS: There were no differences between conditions for peak power, mean power, and total work in each set (P > .05). There were no condition × time interaction effects for any variables tested. The peak core temperature was highest at 30°C (38.06°C [0.31°C]). Overall, the pulse oxygen saturation was higher at 35°C than at 20°C (P < .001; d < 0.8), 25°C (P < .001; d = 1.12 ± 0.54, large), and 30°C (P < .001; d = 0.84 ± 0.53, large). CONCLUSION: Manipulating air temperature between 20°C and 35°C had no effect on performance or core temperature during a typical RSH session. However, the pulse oxygen saturation was preserved at 35°C, which may not be a desirable outcome for RSH interventions. The application of increased levels of ambient heat may require a different approach if augmenting the RSH stimulus is the desired outcome.

Cardiovascular Testing Detects Underlying Dysfunction in Childhood Leukemia Survivors.

PURPOSE: Childhood leukemia survivors commonly develop late-onset cardiovascular disease after treatment with anthracyclines. Resting echocardiogram is the standard procedure for monitoring cardiac health but this method may not be sensitive enough to detect subclinical injury. Exercise echocardiography may provide a viable alternative. METHODS: Nineteen (9 males; age, 19 ± 3 yr) anthracycline-treated survivors of childhood leukemia and 17 (8 males) healthy individuals of similar age (22 ± 2 yr) were recruited. All survivors had normal resting echocardiography upon recruitment. Exercise echocardiography was performed using contemporary imaging techniques. Flow-mediated dilation (FMD), body composition, and cardiorespiratory fitness (V˙O2peak) were assessed to determine predisposition to additional disease. RESULTS: Mitral valve peak flow velocity in late diastole (interaction, P = 0.007) increased from rest in survivors (P = 0.023) and controls (P = 0.020) immediately postexercise but did not recover again in the survivors (exercise-recovery, P = 0.784) after recuperation. Consequently, E/A ratio (interaction, P < 0.001) was lower in the survivors at recovery (P < 0.001). Survivors had reduced FMD (7.88 ± 1.70 vs 9.65 ± 2.83; P = 0.030), maximal and recovery HR (P = 0.001; P < 0.001), minute ventilation (P < 0.001), and V˙O2peak (absolute, 2.64 ± 0.62 vs 3.14 ± 0.74 L·min, P = 0.034; relative, 36.78 ± 11.49 vs 45.14 ± 6.80 mL·kg·min; P = 0.013) compared with controls. They also had higher total body fat (percentage, P = 0.034; mass, P = 0.024) and fat mass in the central (P = 0.050), peripheral (P = 0.039) and visceral (P < 0.001) regions. Survivors matched controls with regard to height (173.0 ± 7.8 cm vs 173.8 ± 9.1 cm; P = 0.796), body mass (76.16 ± 19.05 kg vs 70.07 ± 13.96 kg; P = 0.287) and body mass index (25.2 ± 5.1 vs 22.9 ± 2.7; P = 0.109). CONCLUSIONS: Exercise echocardiography unmasked subclinical diastolic dysfunction that may indicate late anthracycline toxicity in apparently healthy survivors of childhood leukemia. Presence of secondary risk factors indicates increased predisposition to comorbidities and highlights the importance of assessing cardiovascular health during follow-up.

Early markers of cardiovascular injury in childhood leukaemia survivors treated with anthracycline chemotherapy.

BACKGROUND: Cardiovascular disease (CVD) is the leading non-malignant cause of death in childhood cancer survivors. Heightened risk of CVD is often attributable to treatment with anthracycline chemotherapy. Anthracycline-mediated cardiac injury may lie latent for years following cessation of treatment and is therefore often not detected until disease is advanced and aggressive therapy is required. Symptomatic CVD may be preceded by subclinical cardiac and vascular dysfunction. This study aimed to determine whether such dysfunction could be detected in healthy, anthracycline-treated survivors of childhood leukaemia. METHODS: Cardiac magnetic resonance imaging (cMRI) with late gadolinium enhancement and endothelial function were used to characterise pre-clinical stages of CVD. Twenty-two long-term (>5 years survival; age 21 ± 3 years) childhood leukaemia survivors were assessed. All survivors were asymptomatic and had normal resting echocardiography. To exclude potential confounding effects of radiotherapy, no survivors had received this treatment. Twenty-two similarly aged (25 ± 3 years) gender-matched controls were recruited for comparison. RESULTS: Left ventricular ejection fraction was lower in the survivors (55.0 ± 4.6%) compared to the controls (59.4 ± 6.2%; p = 0.010). Further, five survivors (23%) had clinically reduced (<50%) left ventricular ejection fraction. Normalised left ventricular end systolic volume was augmented in survivors (40.0 ± 9.1 mL·m2 vs. 34.5 ± 7.5 mL·m2; p = 0.038). Cardiac MRI did not show any late gadolinium enhancement. High resolution, ultrasound-derived flow mediated dilation was impaired in survivors (6.7 ± 2.1% vs. 8.60 ± 1.91%, p = 0.005). CONCLUSIONS: We detected subclinical changes in cardiovascular structure and function indicative of early disease in anthracycline-treated childhood leukaemia survivors with normal echocardiography. Early detection and characterisation of underlying disease allows for timely intervention and improved outcomes in this at-risk population.

Continuous and intermittent heat acclimation and decay in team sport athletes.

The aim of this study was to compare the impact of continuous (CON) and intermittent (INT) heat acclimation protocols on repeat-sprint performance, and to also assess the degree of performance decay following acclimation. Using a pair-matched, between subjects design, 16 trained male team sport athletes were allocated to either INT (8 sessions over 15 days) or CON acclimation (8 sessions over 8 days) groups. Participants performed a heat tolerance test (HTT) involving 60-min of repeat-sprint cycling with a 10-min half time break (in 35.3 ± 0.7°C, 60.1 ± 4.0%; RH) two days pre- (pre-HTT) and post-acclimation (post-HTT1). Decay was investigated with two further HTT's completed over the next two weeks (post-HTT2 and post-HTT3). Results showed the post-HTT1 performance variables [mean power (pre-HTT; INT = 1002.07 ± 173.74, CON = 1057.10 ± 180.07 / post-HTT1; INT = 1097.11 ± 186.85, CON = 1163.77 ± 184.65 W), mean power (W.kg-1), total work (kJ) and work (J.kg-1)] were greater than pre-HHT (p < 0.001) after acclimation, with no differences between INT and CON. No differences in final core and mean skin temperatures or heart rate existed after INT or CON acclimation, however 30 min measures for thermal sensation, perceived thirst and ratings of perceived exertion (as well as the final measure) were lower in post-HTT1 (p < 0.05) in CON. Performance and thermoregulatory responses in post-HTT2 and 3 were similar to post-HTT1 in both INT and CON. These results indicate that prolonged repeat-sprint exercise in the heat is improved after acclimation involving short, high-intensity cycling sessions using either CON or INT protocols, with performance well-maintained over the subsequent 2 weeks, despite removal of the heat stimulus.

Exercise training improves vascular function and secondary health measures in survivors of pediatric oncology related cerebral insult.

Adolescent and young adult (AYA) survivors of pediatric oncology related cerebral insult are vulnerable to numerous treatment-induced deficits that significantly enhance cardiovascular disease risk. Regular exercise improves endothelial function, fitness, body composition and musculoskeletal function which may reduce predisposition for cardiovascular disease. Here we assessed the feasibility and effectiveness of a 24-week exercise intervention on cardiovascular, physical and metabolic outcomes in this population. Thirteen survivors (6 male, 7 female; median age 19 y (range 16-23 y) were recruited to participate in a 48-week study consisting of a 24-week control period (regular care) followed by a 24-week exercise intervention. Outcome measures were collected at entry (week 0) and following regular care (24-week) and exercise (48-week). Assessed variables included endothelial function (flow mediated dilation, FMD), blood pressure, heart rate (HR), aerobic capacity, anthropometry, body composition, muscular strength (3 repetition maximum testing), muscular endurance (repetitions/min) and physical activity levels (accelerometry). Compared to baseline, delta diameter (p = 0.008) and FMD (p = 0.029) of the brachial artery increased following exercise. Bicep-curl strength also increased following exercise compared to baseline (p = 0.019), while submaximal (6 min mark) measures of ventilation (p = 0.012), rating of perceived exertion (p = 0.012), HR (p = 0.001), absolute (p = 0.000) and relative (p = 0.000) aerobic capacity decreased. Breaks in sedentary time increased (p = 0.043) following exercise compared to regular care. Although the sample was small and heterogeneous, this study demonstrates that exercise is achievable and has positive effects on vascular function, submaximal fitness, local strength and physical activity in a population of AYA survivors of pediatric oncology related cerebral insult.

Maternal circulating adipokine profile and insulin resistance in women at high risk of developing gestational diabetes mellitus.

BACKGROUND: Cytokines produced by adipose and placental tissues (adipokines) have been implicated in the development of gestational diabetes mellitus (GDM). There is, however, limited research regarding the relationship between advancing pregnancy, maternal adipokine profile, insulin resistance and the development of GDM. Furthermore, no studies have investigated these parameters in women with a history of GDM who are at the highest risk of recurrence. This study examined the circulating concentrations of a number of adipokines associated with insulin resistance at two points in pregnancy, and determined whether they were altered in women who developed GDM. METHODS: Non-diabetic women with a history of GDM in a previous pregnancy (n=123) had blood drawn at 14 and 28weeks of pregnancy for GDM diagnosis, together with assessment of a range of adipokine concentrations by multiplex assay (fatty acid-binding protein 4 [FABP4], leptin, chemerin, adiponectin and resistin). RESULTS: With advancing pregnancy, maternal adiponectin concentrations decreased, while leptin and resistin levels increased (p<0.05). In women who developed GDM at 28weeks of pregnancy (42%), fasting and postprandial glucose levels were already significantly elevated by 14weeks (p<0.05), while adiponectin concentrations were lower (p<0.05). Adiponectin remained lower at the time of GDM diagnosis (p<0.05), while the other adipokines were similar between groups at each timepoint. CONCLUSION: Maternal glucose and adipokine profile is altered early in pregnancy in women with a history of GDM who subsequently develop recurrent disease.

Fitness, body composition and vascular health in adolescent and young adult survivors of paediatric brain cancer and cranial radiotherapy.

Background Survivors of paediatric brain cancer and/or cranial radiotherapy (CRT) are at an increased risk of developing serious comorbidities. Established risk factors for chronic disease include central obesity, endothelial abnormalities and diminished fitness. Objectives Here we characterised anthropometry, body composition, bone mineral density (BMD), heart rate (HR), blood pressure (BP), endothelial function, muscular strength and endurance and aerobic fitness in adolescent and young adult (AYA) survivors. Methods Twenty survivors (10 male, 10 female; 20 ± 2 years) were compared with 19 matched controls. Muscular strength was assessed using three repetition maximum tests, while muscular endurance was determined as number of repetitions performed per minute. Peak oxygen uptake (VO2 peak) was assessed on a treadmill using a modified chronotropic protocol. Anthropometric measurements, HR and BP were taken using standard clinical protocols, while body composition and BMD were determined using dual X-ray absorptiometry (DXA). Endothelial function was measured using the flow mediated dilation technique. Results Survivors demonstrated deficits in muscular strength (latissimus dorsi pull-down, p = 0.020; bicep curl, p = 0.009), muscular endurance (squats, p = 0.012; sit-ups, p = 0.030; push-ups, p = 0.013), minute ventilation at peak exericse (p = 0.002) and VO2peak (L/min, p = 0.002; mL/kg/min, p = 0.008; mL/kg LBM/min, p = 0.010). Additionally, survivors had greater waist-to-hip ratios (p = 0.032), resting HR (p = 0.048) and higher percentage of total body (p = 0.017), central (p = 0.009) and peripheral (p = 0.032) fat. Lean body mass (p = 0.004) and BMD (p = 0.005) were lower in the survivor group. Conclusion AYA survivors of paediatric brain cancer and/or CRT exhibit altered body composition, increased resting HR and reduced BMD, muscular strength, muscular endurance and cardiorespiratory fitness compared to controls.

The Effects of Crushed Ice Ingestion Prior to Steady State Exercise in the Heat.

This study examined the physiological effects of crushed ice ingestion before steady state exercise in the heat. Ten healthy males with age (23 ± 3 y), height (176.9 ± 8.7 cm), body-mass (73.5 ± 8.0 kg), VO2peak (48.5 ± 3.6 mL∙kg∙min-1) participated in the study. Participants completed 60 min of cycling at 55% of their VO2peak preceded by 30 min of precooling whereby 7 g∙kg-1 of thermoneutral water (CON) or crushed ice (ICE) was ingested. The reduction in Tc at the conclusion of precooling was greater in ICE (-0.9 ± 0.3 °C) compared with CON (-0.2 ± 0.2 °C) (p ≤ .05). Heat storage capacity was greater in ICE compared with CON after precooling (ICE -29.3 ± 4.8 W∙m-2; CON -11.1 ± 7.3 W∙m-2, p < .05). Total heat storage was greater in ICE compared with CON at the end of the steady state cycle (ICE 62.0 ± 12.5 W∙m-2; CON 49.9 ± 13.4 W∙m-2, p < .05). Gross efficiency was higher in ICE compared with CON throughout the steady state cycle (ICE 21.4 ± 1.8%; CON 20.4 ± 1.9%, p < .05). Ice ingestion resulted in a lower thermal sensation at the end of precooling and a lower sweat rate during the initial stages of cycling (p < .05). Sweat loss, respiratory exchange ratio, heart rate and ratings of perceived exertion and thirst were similar between conditions (p > .05). Precooling with crushed ice led to improved gross efficiency while cycling due to an increased heat storage capacity, which was the result of a lower core temperature.

Regular Exercise to Prevent the Recurrence of Gestational Diabetes Mellitus: A Randomized Controlled Trial.

OBJECTIVE: To investigate the effect of a supervised home-based exercise program on the recurrence and severity of gestational diabetes mellitus (GDM) together with other aspects of maternal health and obstetric and neonatal outcomes. METHODS: This randomized controlled trial allocated women with a history of GDM to an exercise intervention (14-week supervised home-based stationary cycling program) or to a control group (standard care) at 13±1 weeks of gestation. The primary outcome was a diagnosis of GDM. Secondary outcomes included maternal fitness, psychological well-being, and obstetric and neonatal outcomes. A sample size of 180 (90 in each group) was required to attain 80% power to detect a 40% reduction in the incidence of GDM. RESULTS: Between June 2011 and July 2014, 205 women provided written consent and completed baseline assessments. Of these, 33 (16%) were subsequently excluded as a result of an elevated baseline oral glucose tolerance test (OGTT), leaving 172 randomized to exercise (n=85) or control (n=87). Three women miscarried before the assessment of outcome measures (control=2; exercise=1). All remaining women completed the postintervention OGTT. The recurrence rate of GDM was similar between groups (control 40% [n=34]; exercise 40.5% [n=34]; P=.95) and the severity of GDM at diagnosis was unaffected by the exercise program with similar glucose and insulin responses to the OGTT (glucose 2 hours post-OGTT 7.7±1.5 compared with 7.6±1.6 mmol/L; P>.05). Maternal fitness was improved by the exercise program (P<.01) and psychological distress was reduced (P=.02). There were no differences in obstetric and neonatal outcomes between groups (P>.05). CONCLUSION: Supervised home-based exercise started at 14 weeks of gestation did not prevent the recurrence of GDM; however, it was associated with important benefits for maternal fitness and psychological well-being. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov, https://clinicaltrials.gov, NCT01283854.

Enhancing energy expenditure and enjoyment of exercise during pregnancy through the addition of brief higher intensity intervals to traditional continuous moderate intensity cycling.

BACKGROUND: Current guidelines recommend that pregnant women without contraindications should engage in 30 min or more of moderate intensity exercise on most days of the week, however, many women fail to achieve this goal. This study examined the effect of adding brief higher intensity intervals to traditional continuous moderate intensity exercise on energy expenditure and the enjoyment of exercise in late pregnancy. This is important to determine given that any additional energy expenditure resulting from higher intensity intervals may be meaningless if enjoyment is compromised, since long-term adherence will likely be low. METHODS: In this study, 12 healthy pregnant women at 30 ± 1 weeks gestation, aged 35 ± 6 years with a BMI of 27.1 ± 4.3 kg/m(2) performed either 30 min of continuous cycling exercise (CONT) at a steady power output equivalent to 65 % age-predicted heart rate maximum or an equivalent period of interval cycling (INTV) consisting of continuous cycling at the same power output as CONT, but with the addition of six 15-s self-paced higher intensity efforts throughout, performed at regular intervals, on separate occasions in a counterbalanced order. RESULTS: Mean cycling power output, heart rate, oxygen consumption and energy expenditure were higher during INTV compared with CONT (P < 0.05). However, there was no difference in mean rate of perceived exertion between conditions. Enjoyment of exercise was higher with INTV (P = 0.01). CONCLUSIONS: The addition of six 15-s higher intensity intervals to continuous moderate intensity exercise effectively increased energy expenditure by 28 %, at the same time as enhancing the enjoyment of exercise in late pregnancy. While these findings may be specific to recreationally active women, this study provides a rationale for future studies to examine the physiological and psychological responses to regular interval training during pregnancy to optimise exercise prescription. TRIAL REGISTRATION: Australian New Zealand Clinical Trials Registry ACTRN12616000680460 . 25 May 2016 (Registered retrospectively).