If you have any physiology, performance, or nutrition related questions, email Ben at ben@yourgroupride.com.
Several people have asked for this column…I wonder why? The question, “does alcohol after exercise impair performance” seems to be a big concern in the Fort Collins community. There are perhaps two main reasons for this, the multitude of alcohol producing establishments in Fort Collins and the increasing social aspect of cycling. It is now commonplace to end a ride with conversation and a beer. If you are one that is concerned about the performance side of cycling, the question of whether alcohol impairs performance or recovery is an important one. This question of alcohol impairment of exercise performance is a difficult one to answer. The main problem lies in the ill-defined objective measures of “recovery”. What leads to recovery is not known and is still just a subjective feeling. I will highlight the data related to some (although certainly not exhaustive) of the surrogate measures of what is thought to contribute to recover.
One of the biggest concerns for endurance exercise is glycogen repletion. It is true that alcohol has effects on glucose regulation. It is also true that chronic alcohol consumption can lead to liver deterioration over time, which along with skeletal muscle is your main site of glucose regulation. However, these are different situations than acute alcohol consumption after exercise. Probably the best study in this area was performed by a group at the Australian Institute of Sport (do you think they wanted to know?), showed that if you ate the recommended post-exercise carbohydrate meal and alcohol, the alcohol did not impair glycogen replenishment compared to carbohydrate only. However, if you displaced your carbohydrate with alcohol, there was an impairment in glycogen replenishment compared to just carbohydrate. These differences in glycogen repletion were maintained 24 hrs later. Keep in mind that the main reason for carbohydrate consumption after exercise is to replenish glycogen, therefore if beer is your choice for “carbohydrate loading” after exercise, it does not do the trick. Perhaps the best thing to do is mix your first beer with your carbohydrate mix (just kidding). One thing to keep in mind here is that for most of us who do not participate in multiday racing tours on a regular basis, the glycogen repletion on one day may not be a big deal.
The second main area I will cover is protein synthesis. Recall that the ability to make proteins is the most important aspect of adapting to an exercise stress. Although there are many studies in rodents related to alcohol and protein synthesis, these are done at very high doses of alcohol or are over the long term (to investigate alcoholism). Recently a study was done in humans to compare the recommended post-exercise protein intake versus protein with alcohol or carbohydrate with alcohol. The study showed that compared to the protein group, the skeletal muscle protein synthetic response was significantly decreased in the protein plus alcohol and even more in the protein plus carbohydrate. There are a couple of limitations to this study, first it was done after exercise that was meant to simulate a field team sport such as rugby or football so it is not clear yet what happens after endurance exercise. Second, it measured protein synthesis in general and it is not clear which proteins were inhibited. Last, the measurements were only done for up to 8 hrs post-exercise and it is not clear what the 24 hr response would be.
Finally, there is the question of rehydration. A group who are world experts in hydration did the best study in this area. This group used a moderate dehydration exercise protocol and looked at rehydration using a beverage that was 150% the volume of estimated sweat loss and was consumed over the first hour after exercise. To this beverage, there was either 0, 1, 2, or 4% alcohol added. With only the 4% beverage was there a significant increase in urine volume and a decrease in rehydration; the smaller doses of alcohol had no effect on hydration. An additional study extended these findings in that if one was already dehydrated, the diuresis effect of the 4% alcohol was minimal. Thus, hydration status itself has a large effect on whether the alcohol will increase dehydration (if you are already dehydrated, it likely will not).
There are, of course, a couple of words of caution here. Most of these studies were performed with moderate alcohol intake acutely after exercise. There is nothing here that allows me to extend the interpretation to high volumes of intake, what happens in the net balance over 24 hours, or what happens with more regular intake. Also, there are other performance variables that are not evaluated and the overall question of well being (social and emotional) is not considered. Finally, these studies solely considered the ethanol component of drinks and did not consider type of alcohol (beer versus wine versus spirits), which may have differing bioactive compounds. It is pretty safe to say that having a beer or glass of wine in addition to regular good nutrition habits will not impair exercise performance and recovery. However, it is likely that excess alcohol consumption or substitution of alcohol for other food could lead to impairments. It is not exciting advice that moderation is the key, but it is sound advice