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Many of us enjoy a glass or two of wine at night to wind down or a couple of beers post-race. We all know that alcohol is deeply entrenched in our cultures, including sport. But understanding how alcohol impacts your training and body may give you some insight into when to have that drink and to determine some balanced guidelines to follow. Before we get into the physiology, remember that alcohol does not affect everyone equally—personal tolerance also changes depending upon when you last ate and if you are dehydrated.
Alcohol consumption has been shown to negatively affect high-intensity endurance performance through different mechanisms. Firstly, even at low levels (~1oz/30ml), psychomotor skills such as reaction time, hand-eye coordination, accuracy, balance, and complex skilled tasks are compromised. Also, and perhaps more importantly for endurance performance, alcohol influences carbohydrate metabolism: it inhibits liver glucose output during exercise and decreases muscle glucose uptake. As your training session continues and your body is tapping into converting lactate and glycerol back into glucose for fuel, alcohol inhibits the liver’s ability to uptake these precursors, subsequently decreasing gluconeogenesis (the production of new glucose). Also, alcohol in your system during exercise increases cardiovascular strain increasing your heart rate, but without modification of stroke volume.
Looking for power and strength? Forget it, you will just find decreased skeletal muscle strength because of an alteration of nerve conduction, a modulation of membrane excitability and an impairment of muscle membrane transporter function. In a hot environment, you will have greater issues with thermoregulation and performance, not only due to the diuretic effect of alcohol, but also because it is a peripheral vasodilator (meaning more blood flows to the skin and you lose more fluid through evaporation). This compounds dehydration and the central effects on core temperature control.
As for recovery, you might as well have not done your session as the metabolites produced by breaking down the alcohol are highly toxic intermediates that increase catabolism (the body breaking down) within the cell’s mitochondria and reduce protein synthesis by reducing anabolic signalling in the muscle. There is also a knock-on effect on muscle glycogen repletion here due to its suppressive effect on glycogen synthesis.
But wait! There is some good news for endurance athletes who want to enjoy alcohol. The co-ingestion of protein with alcohol reduces the negative effect in the mitochondria (reducing oxidative stress responses). Interestingly enough, this only happens with protein, not with carbohydrate. It seems alcohol and carbohydrate overwhelms the mitochondrial adaptation responses, and promotes cell damage (so much for beer being a great recovery option).
As for when to drink, this might sound obvious but ideally you don’t want to do key sessions hungover. Low-stress activity is fine to increase the metabolism of the alcohol in your system (primarily in your liver) and minimize the negative effects on adaptations. Post-exercise recovery should be your first focus, then have a beer or two (as a beer-protein recovery drink does not sound that appealing!).
For general day-to-day life, low-risk drinking is considered to be no more than two standard drinks in any one day and no more than seven drinks per week for women—and no more than three standard drinks a day and no more than 14 drinks per week for men. Be cognizant when you are training and how alcohol in your system can affect adaptations—and when we do return to racing, remember to take care of post-race recovery nutrition first before having that celebratory drink.