Consumption of alcoholic beverages is common practice for competitive runners and fitness enthusiasts alike. The link between alcohol intake and exercise may be due to their representation of rewarding stimuli capable of stimulating the brain’s reward circuitry. While moderate alcohol intake has been proven to have some health benefits, studies report that there is a negative relationship between excessive alcohol consumption and running performance.
Alcohol consumption has detrimental effects on human physiology including hydration, metabolism, and neurological activity. Affectation of these mechanisms negatively impact exercise performance which includes running. Furthermore, alcohol intake has been shown to affect exercise recovery as well as decrease endurance performance in a dose-dependent manner.
Current available literature surrounding alcohol consumption and running performance present contradicting evidence due to differences in alcohol levels and duration of intake in these investigations. Thus, it is necessary to differentiate the effects of acute and chronic alcohol ingestion and to quantify how much alcohol poses a risk on running performance.
Alcohol and Exercise Use Relation
The effect of heavy alcohol ingestion can be drastic to athletic performance, but moderate alcohol intake may offer some health benefits. Moderate alcohol consumption is defined as two drinks per day for men and one drink per day for women. One standard drink is equivalent to a 12-ounce beer, a 5-ounce glass of wine, or a 1.5-ounce serving of 80-proof distilled spirits.
Studies have shown a decrease in the risk of cardiovascular diseases in moderate drinkers. A glass of wine may raise levels of good HDL cholesterol, but it is important to note that there are numerous ways to increase HDL levels without consuming alcohol.
The effects of alcohol and exercise on the brain is similar in the way it positively stimulates the mesocorticolimbic pathway. This is the reward circuitry responsible for mediation of pleasure and rewarding experiences.
Exercise is recognized as a natural reward due to the release of dopamine, monoamines (such as serotonin and norepinephrine), and endogenous opioids such as endorphins. Alcohol induces the same rewarding effect on humans due to the release of dopamine and increase in endogenous opioids in the mesocorticolimbic neural circuitry.
Exercise and alcohol also affect the hypothalamic-pituitary-adrenal (HPA) axis, which plays an important role in basal homeostasis and stress response. Although exercise disturbs homeostasis, it is foreseeable and voluntary, which in turn stabilizes the HPA axis. This results in better regulation of anxiety. While alcohol use disorders impact the HPA axis with an increase in stress activity in the circuitry, in non-dependent individuals, moderate doses of alcohol curbs anxiety.
Effects of Alcohol on Physiology and Running Performance
Ingestion of alcohol poses multiple detrimental effects on different bodily systems which may in turn affect exercise and running performance. The pathways or mechanisms affected by alcohol include hydration, metabolism, neurological activity, aerobic performance, and recovery.
Alcohol is a diuretic beverage which means that it increases the flow of urine through the inhibition of antidiuretic hormone. An excess of 10 mL of urine is produced for each gram of ethanol ingested. Because of this, an individual consuming alcohol may experience dehydration which is the primary cause of early fatigue in runners. Dehydration is brought about by inadequate hydration and the physiological process of sweating.
When alcohol is consumed prior to running, this contributes to the possible dehydration experienced by runners as its diuretic effect ensues within 20 minutes. However, inhibition of the antidiuretic hormone has been said to last longer when there is continuous intake of alcohol. Thus, while acute consumption obviously seems to be harmful immediately prior to a run, chronic intake also poses harm to running performance.
Alcohol also initially causes peripheral vasodilation of blood vessels which allows enhanced blood flow in peripheral areas such as the skeletal muscles and skin. This is in agreement with the natural process that occurs during running. However, when combined, the peripheral vasodilation exacerbates the dehydration brought about by diuresis due to fluid loss through evaporation on the skin.
Alcohol consumption has several effects on glucose metabolism. The most important pathway affected in relation to running is the reduction in muscle glycogen uptake and storage. Muscle glycogen is broken down into glucose as needed by the body during running. Glucose is in turn used for energy production.
During a run, the body produces energy through immediately available carbohydrates from ingested food, stored fat, and glycogen. The available glycogen usually lasts for about 90 to 120 minutes. Thus, if glycogen stores are reduced due to alcohol intake, endurance is primarily affected.
Gluconeogenesis, the production of glucose from non-carbohydrate sources, is also affected by alcohol consumption. This metabolic pathway is essential in endurance runners as it provides an additional source of glucose for energy. However, alcohol has been proven to impair gluconeogenesis leading to less available glucose, hence reduced endurance.
The effects of alcohol intake on the central nervous system is well known. It causes deficits in balance, reaction time, recognition, memory, and accuracy of fine motor skills. These impairments are brought about by acute intoxication and obviously lead to a disturbance in athletic ability.
Chronic consumption of alcohol, however, leads to sleep disturbances and depression of the central nervous system. A lack of quality sleep negatively impacts rest and recovery. Depression of the central nervous system, on the other hand, affects mood and cognition, thus impairing overall health and motivation. These effects of chronic alcohol intake ultimately lead to poor running performance.
Studies have shown no significant consequence of alcohol on aerobic performance, but other literature have also demonstrated the detrimental effects of alcohol on endurance performance. This is because a threshold exists at which point alcohol becomes detrimental to aerobic performance. Alcohol intoxication exceeding 20mmol/L of ethanol showed deleterious effects on performance.
Muscles and tissues need to recover after a workout. To expedite recovery, a decrease in inflammation is needed. Alcohol, however, causes vasodilation which increases blood flow and swelling to the area. It also reduces the synthesis of proteins needed for muscle repair.
Learn More: Does Alcohol Consumption Affect Muscle Recovery?
Furthermore, because of the strain alcohol puts on the liver, it is believed to slow down recovery and repair. The liver assists in recovery, but regulates blood flow as well. Ingesting alcohol in large doses increases blood flow, which shifts the focus of the organ from assisting in recovery to regulating the blood flow.
The intake of too much alcohol either acutely or chronically has detrimental effects on exercise and running performance because it leads to impairments in human physiology. While total deprivation may seem to be a solution in preventing these detrimental effects, it is unnecessary as the negative effects of alcohol are only observed past moderate drinking. Thus, it is ideal to limit alcohol ingestion to equal to or less than the recommended daily intake.