How does alcohol affect exercise?

Within the realm of sports, alcohol has been viewed as a performance-enhancing drug, a rehydration beverage, a social lubricant and a post-event treat. Although it is generally understood that excess alcohol intake can be detrimental to health, the answer to “how does alcohol affect exercise?” is less clear.

Alcohol consumption is a socially acceptable and expected aspect of team and other sports, and major alcoholic beverage brands often sponsor sports teams and events. Therefore, instead of pretending we can remove alcohol from athlete’s diets, it is more useful to identify which aspects of exercise can be affected by its intake.

How does alcohol affect exercise?

Energy balance

Alcohol is a drug, and as such the body works hard to get rid of it. This means that alcohol is broken down before fat and carbohydrate to be used as energy. As seen in my previous article about macronutrients, each gram of alcohol contributes 29 kilojoules (7 kilocalories) of energy, potentially contributing to weight gain. This is especially concerning for athletes in weight category sports or sports in which body weight influences performance (e.g. endurance sports).

Performance

Available studies have not found a strong detrimental effect of acute alcohol intake on athletic performance. However, this may be due to the fact that the effects of alcohol are highly individual, and that conducting objective, blinded research on this topic is essentially impossible. In the case of aerobic (i.e. endurance or cardiovascular-type exercise), there seems to be a threshold at which alcohol is detrimental to performance. Again, this is likely highly individual and dependent on other factors.

The potential negative effects of alcohol on performance include:

• Alcohol intake is associated with muscle cramps and muscular pain and loss of proprioception.
• Alcohol vasodilates peripheral capillaries, leading to increased fluid losses via sweat. This affects fluid balance and core body temperature, both of which can negatively impact performance.
• Alcohol may cause hypoglycaemia in people with diabetes who take insulin. The normal cognitive impairment that accompanies alcohol consumption can make it difficult for the athlete to identify the hypoglycaemic episode. Sugar-containing alcoholic beverages can cause hyperglycaemia, which can be exacerbated by the exercise-induced breakdown of glycogen.
• Alcohol can trigger some gastrointestinal symptoms such as those of irritable bowel syndrome (IBS), gastritis, and reflux. It can also trigger migraines.
• The adverse effects of alcohol are exacerbated during air travel, worsening the severity of jetlag and impacting performance.
• As a depressant, alcohol can impair several aspects required for athletic performance, including balance, reaction time, visual search, recognition, memory and fine motor skills.
• Athletes experiencing a hangover will likely find it difficult to perform at the same level as in the sober state.

Recovery

Without a doubt the post-exercise window is where alcohol is most often consumed. Unfortunately, this is also the time when recovery practices and processes should take place.

Below are many of the ways in which alcohol impacts recovery:

• Drinking too much alcohol post-exercise can have a negative effect on fluid and food intake (you tend to drink less water and either eat less or eat non-nourishing foods that do not support recovery).
• Alcohol interferes with the ability to resynthesise glycogen post-exercise either directly or indirectly by displacing intake of carbohydrate.
• Alcohol has a diuretic effect, which can affect hydration status. The effect seems to be dependent on alcohol content (greater urinary output with greater percentage) and hydration status (greater urinary output when well hydrated). Studies that have looked at beer as a rehydration drink +/- manipulation of its electrolyte content, have found that subjects still end up in negative fluid balance. Therefore, your best bet is to ensure an aggressive rehydration protocol (with proper electrolyte beverages) when consuming alcohol.
• Alcohol can impair judgement and decision making, potentially leading to neglect of adequate nutrition, injury and recovery management, accidents, etc.
• The alcohol-induced vasodilation of blood vessels on the skin (see Performance section) can hinder recovery from injuries.
• Alcohol usually affects the quantity and quality of sleep, impacting recovery and subsequent performance.
• Alcohol reduces muscle protein synthesis, affecting recovery, muscle growth and performance.
• Alcohol can negatively impact the inflammatory response, impairing the healing of soft tissue and wounds.

Recommendations

• Eat a carbohydrate and protein containing meal after exercising and before drinking to aid recovery and slow down the absorption of alcohol.
• Choose low alcohol beverages when possible.
• Aim at waiting several hours before consuming alcoholic beverages after a session to reduce the impact on glycogen and muscle synthesis.
• Drink in moderation and avoid driving and engaging in risky activities (e.g. swimming) after drinking.
• Minimise drinking when recovering from injuries.
• Ensure adequate hydration with electrolyte-based fluids when drinking alcohol to maintain fluid balance.

References

1. Burke, Louise. Clinical Sports Nutrition, 5th Edition. McGraw-Hill Australia, 09/2015. VitalBook file.
2. Vella LD, Cameron-Smith D. Alcohol, athletic performance and recovery. Nutrients. 2010/08/01. 2010;2(8):781–9.

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