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.

Mixed-Method Precooling Enhances Self-Paced 20-km Cycling Time-Trial Performance When Apparent Temperature Is >46 °C but May Not Be a Priority in <46 °C.

PURPOSE: Precooling (PreC) may only benefit performance when thermal strain experienced by an individual is sufficiently high. We explored the effect of mixed-method PreC on 20-km cycling time-trial (CTT) performance under 3 different apparent temperatures (AT). METHODS: On separate days, 12 trained or highly trained male cyclists/triathletes completed six 20-km CTTs in 3 different ATs: hot-dry (35 °C AT), moderately hot-humid (40 °C AT), and hot-humid (46 °C AT). All trials were preceded by 30 minutes of mixed-method PreC or no PreC (control [CON]). RESULTS: Faster 2.5-km-split completion times occurred in PreC compared with CON in 46 °C AT (P = .02), but not in 40 °C AT (P = .62) or 35 °C AT (P = .57). PreC did not affect rectal and body temperature during the 20-km CTT. Skin temperature was lower throughout the CTT in PreC compared with CON in 46 °C AT (P = .01), but not in 40 °C AT (P = 1.00) and 35 °C AT (P = 1.00). Heart rate had a greater rate of increase during the CTT for PreC compared with CON in 46 °C AT (P = .01), but not in 40 °C AT (P = .57) and 35 °C AT (P = 1.00). Ratings of perceived exertion (P < .001) and thermal comfort (P = .04) were lower for PreC compared with CON in 46 °C AT only, while thermal sensation was not different between PreC and CON. CONCLUSION: Mixed-method PreC should be applied prior to 20-km CTTs conducted in hot-humid conditions (≥46 °C AT). Alternatively, mixed-method PreC may be a priority in moderately hot-humid (∼40 °C AT) conditions but should not be in hot-dry (∼35 °C AT) conditions for 20-km CTT.

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.

Acute exercise affects dual-energy X-ray absorptiometry body composition estimates but not standardised ultrasound measurements of subcutaneous adipose tissue.

Ultrasound has been demonstrated to be a highly accurate and reliable tool for measuring subcutaneous adipose tissue thickness and is robust against changes in hydration status or acute food or fluid intake. However, the effect of prior acute exercise is unexamined. This study examined the impact of an acute endurance exercise and resistance exercise session on standardised brightness-mode ultrasound measurements of subcutaneous adipose tissue thickness compared to skinfolds and dual-energy X-ray absorptiometry body composition estimates. In a randomised cross-over design, 30 active adults (24.2 ± 4.9 years) undertook physique assessment via standardised brightness-mode ultrasound, skinfolds and dual-energy X-ray absorptiometry before, immediately and 45 min after an acute endurance or resistance exercise session. The mean sum of eight subcutaneous adipose tissue thickness measured via standardised brightness-mode ultrasound increased (0.6 mm, p = 0.04) immediately postendurance exercise but was not meaningful when evaluated against the technical error of measurement of the investigator. A significant (p = 0.01) but not meaningful decrease in the sum of eight skinfolds occurred immediately (-1.1 ± 0.4 mm) and 45 min (-1.3 ± 0.4 mm) postresistance exercise. Comparatively, endurance exercise elicited a meaningful decrease of total mass (460 ± 30 g) and trunk lean mass (680 ± 90 g) dual-energy X-ray absorptiometry estimates. Findings from this study indicate standardised client presentation may be unnecessary when employing either standardised brightness-mode ultrasound or skinfolds for body composition assessment unlike dual-energy X-ray absorptiometry.

Food and fluid intake and hydration status does not affect ultrasound measurements of subcutaneous adipose tissue in active adults.

OBJECTIVES: To investigate the impact of acute food and fluid intake or hydration status on the standardised brightness-mode ultrasound measurement of subcutaneous adipose tissue thickness. DESIGN: Thirty active adults (female n = 10) participated in a randomised cross over study. METHODS: Participants completed three body composition assessment sessions via standardised brightness-mode ultrasound and Dual-energy X-ray absorptiometry. Participants were assessed under standardised presentation during 'food only' and 'food plus water' sessions at baseline and reassessed after their allotted intake. 'Hypohydration plus water' was undertaken in a hypohydrated state at baseline and reassessed after water intake. RESULTS: The sum of eight subcutaneous adipose tissue thickness was lower when measured after 'food only' or 'food plus water' compared to baseline (-0.1 to -0.9 mm; p < 0.01). However, these changes were less than the 95% confidence interval of the technical error of measurement of the investigator. Body mass, dual-energy x-ray absorptiometry total and trunk mass, lean mass and trunk lean mass estimates increased (p < 0.01) following 'food only' or 'food plus water', and decreased with hypohydration (p < 0.01). Total and regional fat mass estimates were not impacted. CONCLUSIONS: The sum of eight subcutaneous adipose tissue thickness measured via standardised brightness-mode ultrasound was unaffected by acute food and fluid consumption or hydration status changes. Comparatively, these interventions altered dual-energy x-ray absorptiometry body composition estimates, especially that of lean mass components. Standardised brightness-mode ultrasound can therefore be used to monitor changes in fat patterning when standardised client presentation is not practically achievable.

Measures of body composition via Dual-energy X-ray absorptiometry, ultrasound and skinfolds are not impacted by the menstrual cycle in active eumenorrheic females.

OBJECTIVES: (1) Compare changes in body composition estimates over the menstrual cycle in active females using Dual-energy X-ray absorptiometry, standardised brightness-mode ultrasound and skinfolds (2) Compare the predictability of Dual-energy X-ray absorptiometry fat mass estimate via standardised brightness-mode ultrasound versus skinfolds measurements. DESIGN: Thirty active females (27 ±â€¯5 y) with regularly occurring menstrual cycles participated in a cross sectional study. METHODS: Participants completed four assessment sessions scheduled according to each individual's menstrual cycle. These sessions took place during their (1) early follicular, (2) mid-to-late follicular, (3) mid-luteal and (4) second early follicular phases. Body composition estimates were acquired using Dual-energy X-ray absorptiometry, subcutaneous adipose tissue thickness was measured at eight sites using standardised brightness-mode ultrasound and skinfolds. RESULTS: The sum of eight subcutaneous adipose tissue thickness measured using standardised brightness-mode ultrasound and skinfolds were not different between the cycle phases (p > 0.05). Body mass and Dual-energy X-ray absorptiometry total mass estimate as well as Dual-energy X-ray absorptiometry estimates of total and regional lean and fat mass were also not different between cycle phases (p > 0.05) and any changes were within the 95% confidence intervals of their respective least significant change values. CONCLUSIONS: There were no true and meaningful changes in the sum of eight subcutaneous adipose tissue thickness measured via standardised brightness-mode ultrasound and skinfolds or Dual-energy X-ray absorptiometry total and regional tissue mass estimates across the menstrual cycle in active eumenorrheic females. Body composition may thus be assessed via these methods in this population at any cycle phase with standardised participant presentation.

Strength Training Improves Exercise Economy in Triathletes During a Simulated Triathlon.

PURPOSE: The completion of concurrent strength and endurance training can improve exercise economy in cyclists and runners; however, the efficacy of strength training (ST) implementation to improve economy in long-distance (LD) triathletes has not yet been investigated. The purpose of this study was to investigate physiological outcomes in LD triathletes when ST was completed concurrently to endurance training. METHODS: A total of 25 LD triathletes were randomly assigned to either 26 weeks of concurrent endurance and ST (n = 14) or endurance training only (n = 11). The ST program progressed from moderate (8-12 repetitions, ≤75% of 1-repetition maximum, weeks 0-12) to heavy loads (1-6 repetitions, ≥85% of 1-repetition maximum, weeks 14-26). Physiological and performance indicators (cycling and running economy, swim time, blood lactate, and heart rate) were measured during a simulated triathlon (1500-m swim, 60-min cycle, and 20-min run) at weeks 0, 14, and 26. Maximal strength and anthropometric measures (skinfolds and body mass) were also collected at these points. RESULTS: The endurance strength group significantly improved maximal strength measures at weeks 14 and 26 (P < .05), cycling economy from weeks 0 to 14 (P < .05), and running economy from weeks 14 to 26 (P < .05) with no change in body mass (P > .05). The endurance-only group did not significantly improve any economy measures. CONCLUSIONS: The addition of progressive load ST to LD triathletes' training programs can significantly improve running and cycling economy without an increase in body mass.

Influence of Electronic Devices on Sleep and Cognitive Performance During Athlete Training Camps.

ABSTRACT: Jones, MJ, Dawson, B, Eastwood, PR, Halson, SL, Miller, J, Murray, K, Dunican, IC, Landers, GJ, and Peeling, P. Influence of electronic devices on sleep and cognitive performance during athlete training camps. J Strength Cond Res 35(6): 1620-1627, 2021-This study investigated the effects of removing athletes' electronic devices in the evening on sleep and performance during training camps. Water polo athletes (n = 26) attending a 7-night training camp (study 1) and triathletes (n = 23) attending a 4-night training camp (study 2) were randomly allocated to a no-device group (no electronic devices could be used after dinner or overnight; ND) or control group (unrestricted electronic device use; CON). Sleep was monitored through wrist actigraphy. The ND group completed a questionnaire measuring anxiety related to being unable to use electronic devices ("nomophobia"). Triathletes also completed a psychomotor vigilance test (PVT) at the start and end of camp. Water polo ND athletes went to bed earlier and spent longer time in bed than CON on the first night, but not on other nights. In triathletes, sleep quantity was not different between groups on any night. No statistically significant differences were observed for changes in nomophobia from the first to the last night of camp. No differences in PVT performance were observed between ND and CON triathletes. In conclusion, removal of evening electronic devices does not improve sleep quantity or cognitive performance in athletes during short-duration (4-7 nights) training camps.

Strength Training in Long-Distance Triathletes: Barriers and Characteristics.

ABSTRACT: Luckin, KM, Badenhorst, CE, Cripps, AJ, Landers, GJ, Merrells, RJ, Bulsara, MK, and Hoyne, GF. Strength training in long-distance triathletes: Barriers and characteristics. J Strength Cond Res 35(2): 495-502, 2021-The purpose of this investigation was to identify perceived and physical barriers toward the completion of concurrent strength training and endurance training in long-distance triathletes. Three hundred ninety long-distance triathletes (224 women, 166 men; age [y]: 39 ± 10) completed a 68-question self-administered, semiquantitative survey that assessed endurance and strength training characteristics, experience in triathlon, and perceived barriers regarding the completion of strength training. Mean training hours per week was 14.92 ± 5.25, with 54.6% reporting participation in strength training. Heavy strength training was the most commonly reported (39.4%), with significantly more men completing this form of strength training (p < 0.001). Results from subjects who did not complete strength training indicated that perceived time constraints (53.1%) in addition to lack of knowledge on exercise progression and form (52.5%) are prominent perceived barriers to strength training completion. Identification of the barriers perceived by long-distance triathletes that prevent them from completing concurrent strength training and endurance training may be useful for coaches, athletes, and sports scientists who seek to incorporate strength training for injury prevention and performance improvement.

Body composition assessment in athletes: Comparison of a novel ultrasound technique to traditional skinfold measures and criterion DXA measure.

OBJECTIVES: This investigation compared ultrasound and skinfolds as measures of body fat for athletes, relative to dual-energy X-ray absorptiometry. DESIGN: Fifty-six well-trained athletes from various sports participated in a cross-sectional study. METHODS: The participants attended one testing session, where total body fat mass was measured using dual-energy X-ray absorptiometry, and subcutaneous adipose tissue was measured using brightness-mode ultrasound and skinfolds with callipers. The ultrasound and skinfold measures were correlated independently against standardised fat mass from dual-energy X-ray absorptiometry. RESULTS: The correlation between standardised fat mass and sum-of-eight (Σ8) sites ultrasound (r=0.959, p<0.001), and with sum-of-seven (Σ7) sites skinfolds (r=0.911, p<0.001), were both high positive correlations. In the lowest quartile by fat proportion, the correlation between standardised fat mass and Σ8 ultrasound (r=0.811, p<0.001) was a high positive correlation, whilst the correlation with Σ7 skinfolds (r=0.652, p=0.011) was a moderate positive correlation. In the highest quartile by fat proportion, the correlation between standardised fat mass and Σ8 ultrasound (r=0.847, p<0.001) was a high positive correlation, whilst the correlation with Σ7 skinfolds (r=0.591, p=0.026) was a moderate positive correlation. CONCLUSIONS: Ultrasound and skinfolds are both very good methods to accurately assess body composition in athletes, relative to dual-energy X-ray absorptiometry. However, ultrasound delivered consistently more accurate results, throughout a broad athletic spectrum.

Comparison of Linear and Reverse Linear Periodized Programs With Equated Volume and Intensity for Endurance Running Performance.

Bradbury, DG, Landers, GJ, Benjanuvatra, N, and Goods, PS. Comparison of linear and reverse linear periodized programs with equated volume and intensity for endurance running performance. J Strength Cond Res 34(5): 1345-1353, 2020-This investigation examined the effectiveness of 2 periodization methods on endurance running performance. Thirty recreational runners (25.2 ± 7.4 years; 175.4 ± 8.1 cm; 69.0 ± 9.8 kg) were assigned to 3 groups based on preintervention test results: linear periodization group (LPG, n = 10), reverse linear periodization group (RPG, n = 10), and control group (CG, n = 10). The LPG and RPG completed 3 training sessions (2 supervised and 1 unsupervised) per week in two 6-week blocks. The LPG went through a high-volume training program while the RPG performed higher intensity, lower volume training in the initial block. Training volume and intensity was reversed in the second 6-week training block. All subjects completed pre-training (week 0), midpoint (week 7), and post-training (week 14) testing, which included anthropometric measurements (body mass and sum of 8 skinfolds), treadmill tests for running economy (RE) and V[Combining Dot Above]O2max, and a 5,000-m time trial (TT) on a 400-m grass track. Greater improvements in the 5,000-m TT were observed in the LPG (76.8 ± 55.8 seconds, p = 0.009, d = 1.27) and the RPG (112.8 ± 83.4 seconds, p = 0.002, d = 1.51) than the CG (3.6 ± 59 seconds). No significant differences were found between the LPG and RPG (p = 0.321, d = 0.51). No group differences were found for V[Combining Dot Above]O2peak (p = 0.955) or RE at 9 km·h (p = 0.329) or 11 km·h (p = 0.558), respectively. However, significant improvements were seen in these variables after training: V[Combining Dot Above]O2peak (p = 0.010), RE 9 km·h (p < 0.001), and RE 11 km·h (p = 0.004). These results do not support linear periodization or reverse linear periodization as a superior method; however, periodized training elicited greater improvements in endurance performance than nonperiodized training, highlighting the importance of planned training structure.

Physical and perceptual cooling: Improving cognitive function, mood disturbance and time to fatigue in the heat.

This study investigated the effects of menthol swilling and crushed ice ingestion on cognitive function, total mood disturbance (TMD), and time to fatigue (TTF). Twelve male long-distance runners completed three counterbalanced running trials (3 × 30 minutes at 65% VO2peak and a TTF run at 100% VO2peak ) in hot, humid conditions (35.3 ± 0.3°C, 59.2 ± 2.5% relative humidity). Trials consisted of precooling with crushed ice ingestion and mid-cooling by menthol swilling (MIX), precooling with water ingestion and mid-cooling by menthol swilling (MENTH), and control (CON). Swilling with either 25 mL of menthol solution or placebo occurred upon entry to the heat, at 15-minute intervals during the run and prior to the TTF run. Core temperature, forehead skin temperature, tympanic temperature, perceived thermal sensation, and TMD were significantly lower with MIX compared with MENTH and CON (P < .05). Thirst was satiated in MIX compared with CON; however, MENTH did not have a significant effect. After 90 minutes of running and post-TTF run, fewer errors occurred in the executive control task (P < .05), as well as decision-making and working memory (P > .05; d = 0.5-0.79) between MIX and CON; however, MENTH had no effect compared with CON. The TTF run was significantly longer with MENTH (34.38%; P = .02) and MIX (39.06%; P = .001) compared with CON, with no difference between MENTH and MIX (P = .618). The physical reduction in core and internal head temperature seen with crushed ice ingestion may lead to improvements in cognitive function; however, both MENTH and MIX were sufficient for improving exercise performance.

Enhanced Decision Making and Working Memory During Exercise in the Heat With Crushed Ice Ingestion.

PURPOSE: To examine the effects of precooling via crushed ice ingestion on cognitive function during exercise in the heat. METHODS: Eleven active men ingested either 7 g·kg-1 of crushed ice (ICE) or thermoneutral water (CON) 30 minutes before running 90 minutes on a treadmill at a velocity equivalent to 65% VO2peak in hot and humid conditions (35.0°C [0.5°C], 53.1% [3.9%] relative humidity). Participants completed 3 cognitive tasks to investigate decision making (8-choice reaction time [CRT]), working memory (serial seven [S7]), and executive control (color multisource interference task [cMSIT]) on arrival, after precooling, and after running. RESULTS: Precooling significantly decreased preexercise core (Tcore) and forehead skin temperature in ICE compared with CON, respectively (Tcore 0.8°C [0.4°C], -0.2°C [0.1°C]; Thead -0.5°C [0.4°C], 0.2°C [0.8°C]; P ≤ .05). Postrun, ICE significantly reduced errors compared with CON for CRT (P ≤ .05; d = 0.90; 90% confidence interval, 0.13-1.60) and S7 (P ≤ .05; d = 1.05; 90% confidence interval, 0.26-1.75). Thermal sensation was lower after precooling with ICE (P ≤ .05), but no significant differences were recorded between conditions for cMSIT errors, skin temperature, heart rate, or ratings of perceived exertion or perceived thirst (P > .05). CONCLUSIONS: Precooling via ICE maintained cognitive accuracy in decision making and working memory during exercise in the heat. Thus, ICE may have the potential to improve sporting performance by resisting deleterious effects of exercise in a hot and humid environment on cognitive function.

Internal precooling decreases forehead and core temperature but does not alter choice reaction time during steady state exercise in hot, humid conditions.

This study aimed to determine if precooling via crushed ice ingestion reduces forehead skin temperature (Thead) and core temperature (Tcore) during exercise in the heat and whether it has an effect on choice reaction time (CRT). Ten males commenced a 30 min precooling period, ingesting either 7 g kg-1 of crushed ice (ICE) or room temperature water (CON) prior to cycling 60 min at 55% V̇O2peak in hot, humid conditions (35.0 ± 0.3 °C, 50.2 ± 2.1% Relative Humidity). The CRT task was completed upon arrival and after the precooling period in the lab, then at 15 min intervals during exercise in the heat. Precooling reduced Thead and Tcore to a greater degree in ICE (Thead: -0.8 ± 0.31 °C; Tcore: -0.9 ± 0.3 °C) compared with CON (Thead: -0.2 ± 0.3 °C; Tcore: -0.2 ± 0.2 °C) (p ≤ 0.001). Choice reaction time performance improved throughout the cycle for both conditions (p ≤ 0.05). Ice ingestion lowered thermal sensation (p = 0.003) and skin temperature (d = 0.88; Tskin), while heart rate, ratings of perceived exertion and thirst were similar between conditions (p > 0.05). Precooling effectively reduced Thead and Tcore but did not provide additional improvement in CRT during moderate exercise in the heat. Further investigation is required to determine whether the lower central and peripheral temperature after ice ingestion is beneficial for tasks of greater cognitive effort.