Globally, it is estimated that adults consume approximately 4.3 litres of pure alcohol per year. The World Health Organisation (WHO) has recommended that the daily limit of alcohol for males is four standard drinks per day, where females require half at two standard drinks per day. Depending on your location, a standard drink can differ in strength. The WHO has defined one standard alcohol drink to contain 8g of pure alcohol; however countries such as New Zealand and Japan have defined one alcoholic drink to contain 10g and 19.75g of alcohol respectively.
Alcohol intakes above this in one sitting; 4-6 drinks for males, 2-4 drinks for females can be hazardous to physical and mental health where binge drinking is classified as consuming over 60g of pure alcohol per event – Of which, approximately 16.5% of adults around the world participate in on a weekly basis. Although these generalisations are specific to the non-athletic population, it does not mean that athletes are exempt from this. It would be advisable that athletes completely remove alcohol from their intake; however this is not a practical nor realistic approach due to the prevalence of alcohol in society. Therefore it’s a case of understanding the implications of alcohol on athletic performance and being able to provide sensible guidelines for the athlete to follow.
Evidentially, alcohol consumption in college and university level athletes is reported to be higher in males than females. Where the highest reported were in athletes partaking in Rugby Union, Rugby League and Aussie Rules where alcohol intakes from a single drinking session can be nine times the safe and recommended limit. Of which, drinking sessions are generally a result of social/team bonding, celebrations and initiations that can sometimes be un-ignored in order to be part of the team. Considering that alcohol intakes in athletes can reach concerning amounts, and far greater than their non-athlete counterparts – athlete monitoring is required as this behaviour can be very detrimental to performance and recovery.
As alcohol intake pre exercise is discouraged due to the potential decrements in performance, much of the available evidence examines how alcohol interacts with recovery modalities post exercise. The main areas of concern are; muscle repair, glycogen replenishment, rehydration, hormonal disturbances and immune function.
Alcohol intakes are expressed relative to bodyweight; for example, 1g per kilogram bodyweight (1g/kg/bw). Therefore, if you were to weigh 80kg, then this would equate to 80g of pure alcohol. Considering that the WHO has defined 1 standard drink to contain 8g of alcohol, 80g of alcohol would equate to 10 standard drinks.
Athletic performance is usually accompanied with acute dehydration. It was originally thought that all alcohol post exercise should be avoided as it will impair rehydration strategies through increased urinary output. However, more recent data would suggest that the diuretic effects of alcohol are dependent on the starting hydration status of the athlete. For example, athletes in a hydrated state observe less alcohol induced urinary output when compared to their dehydrated counterparts. Furthermore, it is paramount to understand that the dose makes the poison – research conducted by Shirreffs and Maughan found that the upper limit of alcohol intake of hydration is 0.49g/kg/bw, where impairments in hydration were seen at intakes of 0.92g/kg/bw. Therefore, for hydration purposes only, it would be advisable for athlete to consume under 0.49g/kg/bw in the post exercise period in a pre-hydrated state. I.e. ensure that post exercise hydration status is adequate through water, electrolyte/carbohydrate drinks first prior to consuming alcohol.
Alcohol intake can impact gluconeogenesis , glucose utilisation and glucose uptake into the muscle cell. However, just like it’s affect on hydration status, it appears that alcohol intake on post exercise glycogen replenishment is effected by the carbohydrate status of the athlete. For example, Burke et al compared two high carbohydrate diets; one with high amounts of alcohol (1.5g of alcohol/kg/bw) and one with zero alcohol. The two diets replenished glycogen stores suggesting that alcohol intake has no impact on replenishment if adequate carbohydrates are consumed. However, if alcohol is consumed without the presence of carbohydrates in the diet, i.e. an alcohol ‘displacement diet’, then glycogen resynthesis is impaired. Again, suggesting that carbohydrate intake dictates rates of glycogen storage, not alcohol.
Alcohol consumption in rodents can impair the mechanisms of recovery (muscle protein synthesis) by 75% for up to 24 hours and is most prevalent in fast twitch as opposed to slow twitch muscle fibres. Furthermore, alcohol appears to impair the synthesis of new muscle and has little interaction with muscle protein breakdown. As always, a caveat exists – the dose tested in rats is equal to approximately 24 standard drinks (3.46g/kg/bw). With regards to testing in humans, it would be unethical to get a group of volunteers this drunk, although many student athletes will be proud of such levels of dedication to an alcohol induced session. However, when consuming a more acceptable 12 standard drinks (1.5g/kg/bw) post strength training with adequate recovery nutrition, muscle protein synthesis and the subsequent adaptive process was blunted. Furthermore, after completing a bout of eccentric exercise to induce muscle breakdown and function – alcohol intake of 1g/kg/bw appeared to decrease muscle function and force production, however was not observed to the same extent with half the dose of 0.5g/kg/bw.
Finally, alcohol related sessions may not be advisable during period of injury, as many of the same adaptive mechanisms for exercise are used to recover the injured area. Moreover, alcohol intake appears to decrease blood flow to the muscle via vasoconstriction, therefore can become detrimental to tissue recovery. This is often an excuse used by many athletes as they are not competing, however should be discouraged. Therefore, it may not be practical to consume alcohol during this period if the goal is to maximise strength gains and recovery from injury.
Alcohol consumption in team’s sports is most prevalent. Sports such as rugby require the athletes to have a good level of strength, speed, power and agility. In the days after a bout of drinking (1g/kg/bw), it’s been reported that athletes did not experience any decrements in any of the desirable performance measures or hormonal and endocrine function. Furthermore, hydration status or anaerobic power was not altered 2 days after a game when ~20 standard drinks were consumed when comparing to a group of players following preferable recovery strategies. However, alcohol consumption can reduce sleep quality and quantity. Poor quality sleep can decrease lower body power output the following day – therefore alcohol may have an indirect affect on performance via sleep quality.
Acute alcohol intake is not favourable for immune function and can increase the susceptibility to illness and infections. During an alcohol session, alcohol interferes with the balance of normal inflammatory processes which can result in certain protein molecules that control inflammation to become downregulated. I.e. alcohol interferes with both pro and ant-inflammatory response to trauma or illness. Furthermore, exercise induced immunosupression is common in athletes training very hard; therefore the combination of alcohol to an already suppressed immune system could worsen the outcome. The specific dose on this is still yet to be determined, however excessive intakes will most like compound the situation.
Alcohol intake and it’s affect on recovery probably isn’t as bad as first thought. It should be noted that the majority of studies carried out have been over a few days and it is very unclear what long term effects alcohol has to the athlete. As initially outlined, the affect of alcohol is very much determined by the dose where the excessive and hazardous amounts observed by many athletes post competition should definitely be avoided. Therefore, alcohol can be consumed at a lower dose of 0.5g per kilogram of bodyweight as it is unlikely to negatively impact hydration status, glycogen replenishment, muscle repair and immune response – For an 80kg individual, this equates to ~40g of pure alcohol, or 5 standard drinks. However, alcohol tolerability is different to the individual and should account for nutrition status, mode of exercise undertaken. Alcohol intake above the recommended 0.5g/kg/bw may be associated with bingeing and long term physical, physiological and social harm. Due to the majority of the research being performed in males, it is far less understood how alcohol at the same dosages would affect the female athlete. For now, similar recommendation would be advisable; drink in moderation and avoid binging. Finally, alcoholic indulges can create very high calorie intake for the day. Therefore if an athlete wishes to lose body fat or make weight prior to a competition, then high alcohol intakes can offset a calorie deficit which is the number one priority for changes in body composition.