This study investigated the influence of exercise-induced dehydration on alcohol pharmacokinetics, subjective ratings of impairment, and risk-taking behaviours. Twelve male volunteers participated in 3 experimental trials completed in a randomised cross over design separated by at least 7 days. In one trial, participants exercised to cause dehydration of ~2.5% body weight loss. For the other trials, participants were required to be in a rested and euhydrated state. A set volume of alcohol was then consumed in each trial and participants were monitored over a 4h period. Blood (BAC) and breath (BrAC) alcohol samples were collected throughout and analysed to calculate pharmacokinetic variables associated with the blood alcohol curve. Total urine production, estimates of BrAC, and subjective ratings of intoxication and impairment were also recorded throughout each trial. No difference was found in the pharmacokinetics of alcohol between any of the trial conditions. BrACs were higher than BACs for 2h following alcohol consumption, but lower at measures taken 3 and 4 h post ingestion. Participants' ratings of confusion and intoxication were significantly lower, and they were more willing to drive in the dehydration trial compared with one of the euhydration trials. These findings suggest that dehydration or other physiological changes associated with exercise may have an ability to influence the subjective effects of alcohol and increase the likelihood of risk-taking behaviours such as drink-driving. However, further research is required to examine the effects of alcohol under conditions of exercise-induced fluid loss in order to clarify these findings.
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