The influence of alcohol on physiologic processes and exercise

Ethanol or alcohol is one of the most commonly used/abused drugs in human history. Alcohol can have many effects on exercise physiological performance so it is important to distinguish between chronic use, moderate use, and abuse.  Alcohol is a mind-altering drug that reduces thinking ability, distorts judgment, and acts as a depressant on the body. Research has suggested that alcohol leads to increased dopamine release in the human brain, bringing on feelings of relaxation and happiness. Although this drug is often used during recreation for the purpose of feeling good, it should not be used in combination with exercise because of the serious negative physiological effects that it has on the body.

One of the most easily observable effects of alcohol on the body is dehydration. When alcohol is consumed, anti-diuretic hormone (ADH) is inhibited, causing less water to be absorbed back into the nephrons in the kidneys when urine is cycling through. This causes urine levels to increase, in turn increasing the frequency of urination. With higher levels of water exiting the body, dehydration is likely to occur. This is especially a problem during exercise, when the body is expelling water in the form of sweat as well. It is important to be fully hydrated for a workout; therefore, it is dangerous to consume alcohol before or during exercise. Research has suggested that beverages containing up to 4% alcohol can delay the recovery process from dehydration to rehydration. Alcohol does not only lead to dehydration; it also prevents humans from reaching rehydration in a timely manner, which could be deadly in a situation regarding exercise.

Another important physiological effect that alcohol has on the body deals with blood pressure. Alcohol consumption increases blood and plasma volume, which in turn increases blood pressure. Exercise has a similar effect; the sympathetic immune system is stimulated, leading to vasoconstriction and ultimately increasing blood pressure. To practice safe exercise, it is important not to elevate blood pressure too high beforehand. Research has recommended that alcohol consumption be reduced in order to maintain healthy and safe blood pressure levels. Likewise, it is unsafe to consume alcohol before or during exercise because blood pressure levels may rise to dangerous levels.

Additionally, alcohol negatively effects then skeletal muscle substrate utilization. By decreasing glucose and amino acid utilization, there is decreased energy supply available to the muscle. Alcohol has also been shown to prevent muscle function by impairing the excitation/contraction coupling because the inhibition of calcium channels in the sarcolemma. 

Perhaps the most important physiological effect that alcohol has on the body is that which concerns the heart. Research has shown that intoxication by alcohol directly relates to impairment of cardiac contractility. Depending on how much alcohol was consumed, cardiac contractility was impaired at varying levels; a lighter intoxication lead to less impairment while a heavier intoxication lead to greater impairment. Exercise causes heart rate to increase, requiring a great deal of cardiac contractility. If the heart is impaired because of alcohol intoxication, blood may not be pumped sufficiently throughout the body during exercise. Therefore, if a person plans on exercising, they should either drink lightly or not at all in an attempt to keep their heart working properly. 

Alcohol has also been seen in induce oxidative stress resulting in cardiac dysfunction. However, with exercise the oxidative damage can be reduced by use of the antioxidant system. Most of the negative effects of increased oxidative stress can be seen in aerobic exercise (800m/1500m).