Alcohol and Exercise
There are few studies where the influence of alcohol intake on exercise performance, either before or after, has been assessed. Because of the known debilitating effects of excessive alcohol intake, e.g. alcohol-induced nervousness, alcohol- induced malnutrition, together with metabolic disturbances, it could be expected that excessive alcohol intake could adversely affect exercise performance.
Calorific content: As already stated the energy content of ethanol, 29DH (kJ.g-1) is similar to that of fat, and approximately two fold higher than proteins and carbohydrates. However the production of ethanol’s metabolites will have adverse effects upon cellular metabolism.
Blood Volume: The intake of alcoholic beverages greater than 4% after exercise will reduce the time needed for subsequent hydration of both blood and plasma volume. Alcohol with lower alcohol content, less than 4% will show a similar hydration time to that of water.
Nutrient availability: Since excessive ethanol intake may cause changes in the intestinal mucosa, affecting absorption of a variety of essential nutrients, e.g. minerals, amino acid and glucose, the net result could be a depletion of protein as well as glycogen stores. Alcohol will interfere with carbohydrate metabolism during and after anaerobic exercise decreasing glucose availability. Alcohol intoxication will inhibit the exercise induced increase in serum glucose concentration during exhaustive anaerobic exercise, which may be caused by depressed glucose output due to alcohol-induced decrease in liver. In addition, alcohol before exercise not only inhibits the exercise induced rise in sugar during exercise but also decreases blood sugar content from 10 minutes up to 3h after termination of exercise compared to exercise without alcohol intake. If exercise is taken during alcoholic hangover, serum glucose decreases within 3h to a significantly lower level which can be explained by the rapid re-synthesis of muscle and liver glycogen with decreased glucose production. Alcohol administration before or after exercise will inhibit the post exercise increase in serum fatty acids. This is probably mediated by acetate the end product of alcohol oxidation in the liver (see metabolic changes). In some studies FFA show an increase during alcoholic hangover when exercise is taken. This is presumably mediated by the increased secretion of cortisol and catecholamines during ethanol withdrawal.
Energy metabolism in human muscle: Acute ethanol loading does not appear to cause any significant change of energy metabolism in normal volunteers during exercise. Acute alcoholic myopathy is rare; clinical manifestations are muscle
cramps and rhabdomyolisis. However two thirds of chronic alcohol abusers show sub-clinical myopathies (see musculature: alcoholic cardiomyopathy and alcoholic myopathy) having biochemical, electrophysiological and pathological abnormalities. Patients with chronic alcoholic myopathy usually show a proximal dominant muscle weakness and atrophy, the etiology of which is unknown. Magnetic resonance 31P studies of chronic alcohol abusers during exercise showed significant decreases of intracellular pH and phosphocreatine during exercise, followed by a prompt recovery of phosphocreatine. The reduction of pH is caused by the lactate production during the synthesis of ATP. The rapid recovery of phosphocreatine levels and delayed pH recovery would indicate that sufficient ATP is supplied through the glycolytic pathway. The preference for anaerobic metabolism may be a consequence of insufficient muscle blood flow or aerobic enzyme abnormality owing to mitochondrial dysfunction in chronic alcohol myopathy. Alcohol adversely affects mitochondrial function, such that the ability of the muscle to function at optimum capacity will be impaired.
Blood pressure: The hypertensive effects of alcohol abuse have been reviewed. Running does not abate this ethanol-induced hypertensive effect, regardless of the exercise the alcohol-induced increase in blood pressure will remain increased.
HDL Cholesterol: Ethanol, when consumed in moderate amounts, will elevate HDL cholesterol (approximately 2 glasses red wine/day) which is a protective factor against coronary heart disease. In addition, running will also elevate HDL cholesterol such that runners who drink a moderate amount of alcohol have high HDL cholesterol, greater than 1.55 mmol/l.
Alcohol and running contribute independently to higher HDL cholesterol concentration that is a protective factor for coronary