Alcohol and Running: The Real Effects on Performance

That post-race beer is practically sacred in many running clubs. Marathons even hand them out at the finish line. And let's be honest, many of us enjoy a nice glass of wine in the evening after a long run. But does it really undo all our hard work? I wanted to get to the bottom of it, and I've read quite a bit on the topic. Spoiler alert: it's not a black-and-white issue.

As always, I'm not a doctor—just a runner who likes to understand what's happening in their body. No moralizing here.

Muscle Recovery Takes a Hit

This is probably the most inconvenient effect for us runners. After a tough workout, the body repairs and strengthens muscles—that's how we improve. The problem is, alcohol slows this process down. According to a widely cited study I encountered, moderate to heavy drinking after intense exercise reduces this muscle repair by 24 to 37%. This happens even when you're consuming protein alongside it.

In plain terms: if you drink 4-5 alcoholic beverages the evening after an interval workout, you're effectively wasting some of the benefits of your session. Just one drink? The impact is likely negligible. It's truly the dose that makes the poison here. And timing also matters: the closer it is to your workout, the more detrimental it can be.

Sleep: The Classic Trap

“Alcohol helps me sleep”—we hear that all the time. And it's true that it can help you fall asleep. But the quality of sleep afterward? That's a different story. Alcohol wrecks deep sleep—precisely the phase where the body repairs itself the most. The result: you might sleep 8 hours, but you're recovering as if you only slept 5.

What convinced me? Check your resting heart rate the morning after a night of drinking, especially if you have a fitness tracker. It's often 5 to 15 beats per minute higher. That's a clear sign your body didn't recover well overnight.

Dehydration: Real, But With Nuance

Alcohol does increase urination—that's a fact. But the effect largely depends on what you drink. A 5% beer is still 95% water. According to some studies, light beers (under 4%) might even contribute positively to rehydration after exercise. Now, that's not an argument to replace water with beer, but it's less dramatic than often portrayed.

On the other hand, spirits and wine are truly dehydrating. And crucially, the danger lies in replacing water with alcohol after a long run in direct sunlight. The combination of dehydration + alcohol + heat is definitely not good. Our tool on the impact of temperature clearly shows how vital fluids are in hot weather.

The Calories: They Add Up

Alcohol packs 7 calories per gram—almost as much as fat. A glass of wine: 120-130 calories. A pint of beer: 200-250 calories. A cocktail: 200-400 calories. And all of that comes with zero useful nutrients—no protein, no vitamins.

The tricky part is that as long as there's alcohol in your bloodstream, your body prioritizes its elimination instead of burning fat. Just one alcoholic drink can "cancel out" a good portion of the calories burned during your run—the calorie calculator helps put that into perspective. This doesn't mean a single glass of wine will make you gain weight, but if you're trying to lean out, regular consumption can definitely be a hinderance.

Immunity: Be Wary During High-Volume Training

After intense exercise, your immune system is temporarily weakened—this is known as the 'open window' (a 3 to 72-hour period when you're more susceptible to catching a cold or sore throat). Alcohol further compromises immunity during this time. If you're in the middle of a marathon training block, this is a risk worth considering.

That said, very moderate consumption (one drink per day max) doesn't seem to pose an issue according to some studies. But be careful with the definition of 'moderate'—what many people consider one drink is often two or three in reality.

Running with a Hangover: We've All Been There

Let's be honest: most runners have done it at least once. And objectively, it's terrible. Coordination is impaired, the effort feels harder, VO₂max is potentially reduced, and heat tolerance decreases. It takes your body 24 to 48 hours to completely eliminate the toxic byproducts of alcohol.

The real question for me is the opportunity cost. Every night of heavy drinking followed by a subpar workout is a partially wasted session. Over a 12-16 week marathon prep, that really adds up.

But Life Isn't Just About Performance

It would be disingenuous to talk only about physiology. Running is often social—the shared moments at the club, the post-race celebrations (the "third half"), are part of the enjoyment and motivation. A runner who forbids everything out of an obsession with performance risks not fully enjoying their sport. Weight management should never become a source of anxiety.

The idea is to make informed choices. One drink after an easy Wednesday run? No big deal. Five drinks the night before your threshold workout? That's a different story.