Josh Foster

The Impact of Different Environmental Conditions on Cognitive Function: A Focused Review.

Cognitive function defines performance in objective tasks that require conscious mental effort. Extreme environments, namely heat, hypoxia, and cold can all alter human cognitive function due to a variety of psychological and/or biological processes. The aims of this Focused Review were to discuss; (1) the current state of knowledge on the effects of heat, hypoxic and cold stress on cognitive function, (2) the potential mechanisms underpinning these alterations, and (3) plausible interventions that may maintain cognitive function upon exposure to each of these environmental stressors. The available evidence suggests that the effects of heat, hypoxia, and cold stress on cognitive function are both task and severity dependent. Complex tasks are particularly vulnerable to extreme heat stress, whereas both simple and complex task performance appear to be vulnerable at even at moderate altitudes. Cold stress also appears to negatively impact both simple and complex task performance, however, the research in this area is sparse in comparison to heat and hypoxia. In summary, this focused review provides updated knowledge regarding the effects of extreme environmental stressors on cognitive function and their biological underpinnings. Tyrosine supplementation may help individuals maintain cognitive function in very hot, hypoxic, and/or cold conditions. However, more research is needed to clarify these and other postulated interventions.

Acute acetaminophen (paracetamol) ingestion improves time to exhaustion during exercise in the heat

•  What is the central question of this study? Acetaminophen (paracetamol) is an analgesic and antipyretic, which has been shown to improve self‐paced cycling performance through a reduction in pain. We sought to ascertain whether acetaminophen could improve time to exhaustion during exercise in the heat through its antipyretic action. •  What is the main finding and its importance? An acute dose of acetaminophen allowed participants to cycle significantly longer in hot conditions by a mean of 4 min (+17%). This was accompanied by significantly lower core, skin and body temperature, and participants found the exercise less of a thermal strain. These findings suggest that acetaminophen may reduce the thermal challenge of exercise in hot conditions.

Effect of Acetaminophen Ingestion on Thermoregulation of Normothermic, Non-febrile Humans

In non-febrile mouse models, high dose acetaminophen administration causes profound hypothermia. However, this potentially hazardous side-effect has not been confirmed in non-febrile humans. Thus, we sought to ascertain whether an acute therapeutic dose (20 mg⋅kg lean body mass) of acetaminophen would reduce non-febrile human core temperature in a sub-neutral environment. Ten apparently healthy (normal core temperature, no musculoskeletal injury, no evidence of acute illness) Caucasian males participated in a preliminary study (Study 1) to determine plasma acetaminophen concentration following oral ingestion of 20 mg⋅kg lean body mass acetaminophen. Plasma samples (every 20 min up to 2-hours post ingestion) were analyzed via enzyme linked immunosorbent assay. Thirteen (eight recruited from Study 1) apparently healthy Caucasian males participated in Study 2, and were passively exposed to 20°C, 40% r.h. for 120 min on two occasions in a randomized, repeated measures, crossover design. In a double blind manner, participants ingested acetaminophen (20 mg⋅kg lean body mass) or a placebo (dextrose) immediately prior to entering the environmental chamber. Rectal temperature, skin temperature, heart rate, and thermal sensation were monitored continuously and recorded every 10 min. In Study 1, the peak concentration of acetaminophen (14 ± 4 μg/ml) in plasma arose between 80 and 100 min following oral ingestion. In Study 2, acetaminophen ingestion reduced the core temperature of all participants, whereas there was no significant change in core temperature over time in the placebo trial. Mean core temperature was significantly lower in the acetaminophen trial compared with that of a placebo (p < 0.05). The peak reduction in core temperature in the acetaminophen trial was reached at 120 min in six of the thirteen participants, and ranged from 0.1 to 0.39°C (average peak reduction from baseline = 0.19 ± 0.09°C). There was no significant difference in skin temperature, heart rate, or thermal sensation between the acetaminophen and placebo trials (p > 0.05). The results indicate oral acetaminophen reduces core temperature of humans exposed to an environment beneath the thermal neutral zone. These results suggest that acetaminophen may inhibit the thermogenic mechanisms required to regulate core temperature during exposure to sub-neutral environments.

Is prostaglandin E2 (PGE2) involved in the thermogenic response to environmental cooling in healthy humans

Prostaglandin E2 (PGE2) is an eicosanoid derived from cyclooxygenase, an enzyme responsible for the cyclisation and oxygenation of arachidonic acid. In response to bacterial infection, PGE2 binds to EP3 receptors on a population of GABAergic neurons in the pre-optic area. Activation of the EP3 receptor decreases the intracellular cyclic adenosine monophosphate (cAMP) concentrations of these neurons, and the resulting dis-inhibition activates spinal motor outputs responsible for shivering thermogenesis, tachycardia, and brown adipose tissue activation. These involuntary responses increase core body temperature to varying degrees depending on the magnitude of infection; an immune response which is crucial for the survival of the host. However, evidence in animal and human models, primarily through the use of cyclooxygenase inhibitors (which block the production of PGE2), suggests that PGE2 may also be an important molecule for the defence of core temperature against body cooling and cold stress (in the absence of fever). In this paper, evidence within human and animal models is discussed which supports the hypothesis that the eicosanoid PGE2 has a role in maintaining human core temperature during environmental cooling. Given that over-the-counter PGE2 inhibiting drugs [i.e. Non-Steroidal Anti Inflammatory Drugs (NSAIDS)] are frequently used worldwide, it is possible that the use of such medication during environmental cooling could impair ones ability to thermoregulate. Support for such findings could have major implications in the pathology of hypothermia, thus, we suggest that future researchers investigate this specific hypothesis in vivo, using healthy human models. Suggestions for the implementation of such experiments are provided in the present work.

Reply to letter: Acetaminophen and sport performance: doping or what?

effect of acetaminophen, although the subsequent results have shown that it does improve performance. Conse-quently, we would like to re-emphasise that we do not con-done the use of acetaminophen in sport as a performance aid, on both safety and ethical grounds.Although we have demonstrated that acetaminophen is capable of moderating the rise in core and skin temperature during exercise in the heat (which improved time to exhaus-tion) (Mauger and hopker 2014) and that it improves cor-ticospinal excitability in resting conditions (Mauger and hopker 2013), we believe that its primary mechanism of action is through analgesia. If this is the case, then any intervention (drug, dietary or otherwise) which can reduce the sensation of pain during moderate-long, dynamic rhyth-mical exercise has the potential to improve performance. Acetaminophen is globally available, has a very high inci-dence of use and is generally considered safe at therapeu-tic doses. Conversely, other analgesics such as tramadol, diclofenac, codeine and hydrocodone are not widely avail-able (but anecdotally are widely used by amateur athletes) and pose greater threats to health and/or are highly addic-tive. therefore, we suggest that there are other analgesics, which are currently being used to improve sporting perfor-mance, which should be addressed as a priority.Professors Lippi and Sanchis-Gom highlight the defini-tion of doping, according to the International Federation of Sports Medicine, as the deliberate or inadvertent use of sub-stances or methods to produce an unfair athletic advantage. Based on this (and the research evidence we present), they suggest that acetaminophen is included in the WADA list of banned substances (subject to therapeutic Use Exception). While we do not disagree that acetaminophen is likely a performance aid, the same definition would have to apply to wide variety of substances, which are routinely used in sport to aid performance yet not currently controlled

Chronic probiotic supplementation with or without glutamine does not influence the eHsp72 response to a multi-day ultra-endurance exercise event

Probiotic and glutamine supplementation increases tissue Hsp72, but their influence on extracellular Hsp72 (eHsp72) has not been investigated. The aim of this study was to investigate the effect of chronic probiotic supplementation, with or without glutamine, on eHsp72 concentration before and after an ultramarathon. Thirty-two participants were split into 3 independent groups, where they ingested probiotic capsules (PRO; n = 11), probiotic + glutamine powder (PGLn; n = 10), or no supplementation (CON; n = 11), over a 12-week period prior to commencement of the Marathon des Sables (MDS). eHsp72 concentration in the plasma was measured at baseline, 7 days pre-race, 6-8 h post-race, and 7 days post-race. The MDS increased eHsp72 concentrations by 124% (F[1,3] = 22.716, p < 0.001), but there was no difference in the response between groups. Additionally, PRO or PGLn supplementation did not modify pre- or post-MDS eHsp72 concentrations compared with CON (p > 0.05). In conclusion, the MDS caused a substantial increase in eHsp72 concentration, indicating high levels of systemic stress. However, chronic PRO or PGLn supplementation did not affect eHsp72 compared with control pre- or post-MDS. Given the role of eHsp72 in immune activation, the commercially available supplements used in this study are unlikely to influence this cascade.

Corrigendum: Effect of Acetaminophen Ingestion on Thermoregulation of Normothermic, Non-febrile Humans

If you believe this document infringes copyright then please contact the KAR admin team with the take-down information provided at http://kar.kent.ac.uk/contact.html Citation for published version Foster, Josh and Mauger, Alexis R. and Thomasson, Katie and White, Stephanie and Taylor, Lee (2016) Effect of Acetaminophen Ingestion on Thermoregulation of Normothermic, Non-febrile Humans. Frontiers in pharmacology, 7 . p. 54.

Effect of tyrosine ingestion on cognitive function and load carriage performance in the heat

Prolonged exercise-heat-stress impairs both exercise performance and cognitive function. Military based operations are often performed in hot environmental conditions and thus performance and safety may be compromised which could be potentially life threatening. Ingestion of tyrosine (TYR), a catecholamine precursor has been shown to improve exercise performance [1] and cognitive function [2] in hot environments, but no study has assessed the effects of TYR in a simulated military setting in the heat simultaneously assessing steady sate exercise performance, time-trial performance and alterations in various facets of cognitive function. Therefore, the aim of this study was to investigate the effect of 150 mg.kg TYR on steady state exercise, cognitive function and time-trial performance in the heat.