Like most of the population, athletes and those who exercise regularly often consume alcohol. It has been reported that alcohol ingestion constitutes up to 5% of the total daily energy consumption in elite athletes and is especially common in team sports where it is encouraged as part of team bonding, but it is also associated with stress relief.
Alcohol has a wide range of negative effects on human physiology affecting metabolism, function of the nervous, cardiovascular and skeletal muscle systems, and regulation of fluid balance and body temperature. However, the impact of alcohol in the periods in and around exercise performance has been less well investigated.
Given that there is a wide range of complex mechanisms by which alcohol affects the human body, it is easy to see that increased blood alcohol concentration has the potential to impair performance in a majority of sports and during exercise.
It is well known that alcohol exerts negative effects on the central nervous system, muscle energy stores and the cardiovascular system. Contrary to popular belief, alcohol is not used by skeletal muscles as a source of energy. Alcohol is oxidised in the liver. Alcohol has been shown to damage muscular work capacity and, as a result, cause a decrease in overall performance levels, affect temperature regulation during exercise, and increase the onset of muscle fatigue. Alcohol intake has also been demonstrated to inhibit liver glucose release during exercise, which is essential to maintain normal blood glucose levels, which can ultimately lead to hypoglycaemia. Alcohol also affects a variety of psychomotor skills, such as balance, reaction time and coordination.
However, some positive effects have also been observed with alcohol consumption. In moderate amounts, alcohol decreases pain and anxiety, which might be beneficial to performance in certain sports. Alcohol may also modulate the ratings of perceived exertion, but this is a fine balancing act and the risk versus reward of consuming alcohol before sports needs to be considered very carefully.
In terms of aerobic and endurance performance it has been shown that alcohol has a detrimental effect. It is important to note that there seems to be a threshold at which alcohol becomes detrimental to aerobic performance; this is 20 mMol/L of alcohol intoxication. Further research has demonstrated that this cause-effect relationship may occur in a dose-dependent manner.
During high intensity exercise that relies on our anaerobic metabolism, despite the known effects of alcohol on skeletal muscle and the nervous system, scientists have failed to establish a cause-effect relationship between alcohol and anaerobic performance. A few studies have been carried out, however, these have shown contradicting results, indicating a lack of knowledge, to date, of the effects of alcohol consumption on anaerobic performance.
Recent research has suggested however that regular alcohol consumption may impair the pathways that allow us to build new muscle proteins, and this then might affect a person’s capacity to recover effectively. It is therefore suggested that for those who are involved in strength sports or looking to build muscle where muscle breakdown and recovery is part and parcel of the process that alcohol should be consumed in moderation and only periodically on special occasions.
To summarise, the negative impact that alcohol has on the human body has been well documented. However, there is a lack of knowledge of the effects of alcohol on certain aspects of exercise performance. The few studies available have shown a dose-dependent cause-effect relationship in the context of aerobic performance. However, for anaerobic performance, studies have failed to establish a relationship between alcohol and performance, with contradicting results.
Athletes are therefore advised to abstain from drinking alcohol before intense exercise. For those who cannot refrain from consuming alcohol, they are recommended to avoid alcohol beyond a social drinking amount for a minimum of 48 hours before the event.
Paul Rimmer (BSc, MSc, PhD).
