Findings regarding the influence of passive heat exposure on cognitive function remain equivocal due to a number of methodological issues including variation in the domains of cognition examined. In a randomized crossover design, forty-one male participants completed a battery of cognitive function tests [Visual Search, Stroop, Corsi Blocks and Rapid Visual Information Processing (RVIP) tests] prior to and following 1 h of passive rest in either hot (39.6 ± 0.4°C, 50.8 ± 2.3% Rh) or moderate (21.2 ± 1.8°C, 41.9 ± 11.4% Rh) conditions. Subjective feelings of heat exposure, arousal and feeling were assessed alongside physiological measures including core temperature, skin temperature and heart rate, at baseline and throughout the protocol. Response times were slower in the hot trial on the simple (main effect of trial, P < 0.001) and complex (main effect of trial, P < 0.001) levels of the Stroop test (Hot: 872 ± 198 ms; Moderate: 834 ± 177 ms) and the simple level of the visual search test (Hot: 354 ± 54 ms; Moderate: 331 ± 47 ms) (main effect of trial, P < 0.001). Participants demonstrated superior accuracy on the simple level of the Visual Search test in the hot trial (Hot: 98.5 ± 3.1%; Moderate: 97.4 ± 3.6%) (main effect of trial, P = 0.035). Participants also demonstrated an improvement in accuracy on the complex level of the visual search test following 1 h passive heat exposure (Pre: 96.8 ± 5.9%; Post: 98.1 ± 3.1%), whilst a decrement was seen across the trial in the moderate condition (Pre: 97.7 ± 3.5; Post: 97.0 ± 5.1%) (time*trial interaction, P = 0.029). No differences in performance were observed on the RVIP or Corsi Blocks tests (all P > 0.05). Subjective feelings of thermal sensation and felt arousal were higher, feeling was lower in the hot trial, whilst skin temperature, core temperature and heart rate were higher (main effects of trial, all P < 0.001). The findings of the present study suggest that response times for perception and executive function tasks are worse in the heat. An improvement in accuracy on perceptual tasks may suggest a compensatory speed-accuracy trade-off effect occurring within this domain, further highlighting the task dependant nature of heat exposure on cognition.

It has previously been suggested that heat exposure and hypohydration have negative effects on cognitive performance, which may impact upon sporting performance. The aim of the present study was to examine the independent effects of heat stress and hypohydration on cognitive performance in elite female field hockey players. Eight unacclimatised elite field hockey players (age: 22 ± 3 y; height: 1.68 ± 0.05 m; body mass: 63.1 ± 6.0 kg) completed a cognitive test battery before and after 50 min of field hockey specific exercise on a treadmill in four experimental trials; two in hot conditions (33.3 ± 0.1 °C), and two in moderate (16.0 ± 3.0 °C), both with and without ad libitum water intake. On the visual search test, participants were faster overall in the heat (1941 vs. 2104 ms, p = 0.001). Response times were quicker in the heat on the Sternberg paradigm (463 vs. 473 ms, p = 0.024) and accuracy was improved (by 1.9%, p = 0.004). There was no effect of hydration status on any of the markers of cognitive function. Overall, the findings suggest that in elite field hockey players exposure to heat enhances response times and/or accuracy on a battery of cognitive function tests. However, hypohydration does not appear to affect cognitive performance in elite field hockey players.

Despite the known positive effects of acute exercise on cognition, the effects of a competitive team sport match are unknown. In a randomized crossover design, 20 female and 17 male field hockey players (19.7 ± 1.2 years) completed a battery of cognitive tests (Visual Search, Stroop, Corsi Blocks, and Rapid Visual Information Processing) prior to, at half-time, and immediately following a competitive match (or control trial of seated rest); with effect sizes (ES) presented as raw ES from mixed effect models. Blood samples were collected prior to and following the match and control trial, and analyzed for adrenaline, noradrenaline, brain derived neurotrophic factor (BDNF), cathepsin B, and cortisol. The match improved response times for a simple perception task at full-time (ES = –14 ms; P < 0.01) and response times on the complex executive function task improved at half-time (ES = –44 ms; P < 0.01). Working memory declined at full-time on the match (ES = –0.6 blocks; P < 0.01). The change in working memory was negatively correlated with increases in cortisol (r = –0.314, P = 0.01; medium), as was the change in simple perception response time and the change in noradrenaline concentration (r = –0.284, P = 0.01; small to medium). This study is the first to highlight the effects a competitive hockey match can have on cognition. These findings have implications for performance optimization, as understanding the influence on specific cognitive domains across a match allows for the investigation into strategies to improve these aspects.

Despite optimal cognitive function being essential for performance, there is a lack of research on the effectiveness of combined cooling interventions on team sport athlete's cognitive function when exercising in the heat. In a randomised, crossover design, 12 unacclimatised men (age: 22.3 ± 3.0 years, body mass: 73.4 ± 5.1 kg, height: 181.0 ± 5.3 cm and max: 51.2 ± 9.5 mL/kg/min) participated in a control (CON) and combined cooling trial (ice slurry and ice collar; COOL). A battery of cognitive tests were completed prior to, during (at half‐time) and following a 90‐min intermittent running protocol in the heat (33°C, 50% relative humidity (RH)). Perceptual and physiological measures were taken throughout the protocol. In CON, response times were quicker on the Stroop task complex level (p = 0.002) and the visual search test complex level at full‐time (p = 0.014) compared to COOL. During COOL, response times were quicker at half‐time on the Stroop task complex level (p = 0.024) compared to CON. Lower rectal temperatures were seen during COOL (CON: 37.44 ± 0.65°C and COOL: 37.28 ± 0.68°C) as well as lower skin, neck and forehead temperatures (main effect of trial, all p < 0.05). Lower ratings of thermal sensation and perceived exertion and enhanced thermal comfort were recorded during COOL (main effect of trial, all p < 0.05). Whilst minimal differences in cognitive function were found when using the combined cooling intervention, the findings highlight a practical and effective strategy to improving many physiological and perceptual responses to intermittent exercise in the heat.

Transcranial magnetic stimulation (TMS) provides an indication of changes occurring in the corticospinal pathway. This study aimed to determine the between-day (trials 1 week apart) and within-day (trials 1 h apart) reliability of TMS and peripheral nerve stimulation. 22 male participants (age 23 ± 4 years; height 1.80 ± 0.07 m; body mass 75.1 ± 11.7 kg; body mass index 23.1 ± 2.5 kg.m−2) completed 2 familiarisation sessions and 3 experimental trials (trial 2 and 3 split by 1 h). The interpolated twitch technique was used to determine TMS-assessed voluntary activations (VA-TMS) superimposed on submaximal and maximal leg extension performed on a custom-built dynamometer. Reliability was assessed using equivalence tests, systematic error, 95% limits of agreement, intraclass correlation coefficient (ICC) and coefficient of variation (CV). VA-TMS was equivalent between-day (94.1 ± 4.4% versus 93.7 ± 4.9%, P < 0.01) and within-day (93.7 ± 4.9% versus 93.7 ± 4.8%, P < 0.01). Systematic error (95% limits of agreement) for VA-TMS was −0.5% (−5.1%, 4.2%) for between-day and − 0.0% (−5.3%, 5.4%) for within-day. ICC and CV values demonstrated high reliability between-day (ICC = 0.93, CV = 2.5%) and within-day (ICC = 0.92, CV = 2.9%). Results indicate that TMS can reliably estimate the output of the motor cortex to the knee extensors, both between-day and within-day. The findings have been used to estimate sample sizes for this technique for future research.

Cyclists routinely train and/or compete in environments that would be considered extreme. More widely, visiting, training, and competing in extreme environments is also becoming increasingly common in recreational cycling, not least as a consequence of heat waves and climate change. Extreme environments typically consist of heat or cold stress, and/or terrestrial altitude or simulated hypoxia. Exposure to extreme environments places additional strain on the human body during exercise, increasing energy demands. An understanding of how different environments, specifically heat, cold, and altitude influence cyclists, helps to identify potential interventions which can support or enhance performance in these conditions. This chapter summarises the physiological challenges within extreme environments, and how they may be mitigated through nutritional interventions. <!----> <!----> <!----> <!---->