It has become standard practice for many people to have a few drinks before engaging in exercise. The dual justifications are often given that, firstly, a little alcohol can actually improve sporting performance, and that, secondly, any negative effects of the alcohol will be more than compensated for by the benefits of the exercise. Both these rationalisations need to be called into question.
Research has indeed shown that small amounts of alcohol do increase muscular endurance and the output of strength, but these types of benefits are very short lived. After 20 minutes or so, the negative effects begin to surface, and these easily outweigh the benefits. The negative dimensions of alcohol consumption include reduced strength and endurance, diminished aerobic capability, longer recovery time, a decrease in the body's ability to metabolize fat, and even a retardation in muscle growth!
Alcohol also effects your central nervous system and brain. Over the long term, significant alcohol consumption can cause severe deterioration of the central nervous system, but even in the short term, nerve muscle interaction is reduced, which results in a loss of strength.
Alcohol consumption likewise effects the heart and circulatory system. Drinking leads to the body to lose heat though the stimulation of the blood vessels that causes them to dilate. This is experienced as a loss in endurance capabilities.
Muscles become relatively cold and therefore become slower and weaker during muscle contractions.
It is the effect of alcohol on the blood that effects recovery time after and during sport. Regular alcohol consumption can cause long-term inflammation of the muscle cells, which reduces the functionality of muscle contractions. This is experienced as increased muscle soreness after exercise, and the discovery that it takes longer for the body recuperate.
Drinking alcohol can also cause digestive and nutrition issues as well. Alcohol consumption triggers a release of insulin in the blood that in turn increases the metabolism of glycogen, which makes fat loss far more difficult. Due to alcohol inhibiting the absorption of key nutrients, it can also lead to anemia and vitamin deficiency (especially with the B type vitamins).
As to the benefits of exercise balancing out the negative effects of alcohol consumption, it needs to be noted further that the areas of the body that most benefit from exercise and not necessarily those that are most damaged by alcohol.
The liver is the most obvious organ targetted in alcohol poisening, as it is the liver that detoxifies alcohol. The more you drink, the harder your liver has to work, and no amount of exercise is going to directly help retore damaged liver cells.
Similarly, since alcohol is diuretic, drinking large amounts of alcohol puts a lot of stress on your kidneys as well. During diuretic action, the hormones are secreted, which leads to heightened water retention, and no one who takes their exercise seriously will want this to happen.
The message for athletes here is simple: if you want to drink alcohol, make sure you do it in moderation and never drink before exercise. Even a small amount of alcohol consumed before sport will almost inevitably reduce the benefits of the exercise activity for the body as well as reduce sporting performance.