Chocolate Milk Study

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Chocolate Milk Study

Post by Vincent on Sat Mar 15, 2008 8:53 pm

A friend of mine at McGill put this together while procrastinating his masters...

As some of you are aware, there has been an on going dialog regrading different effective recovery drinks (ie chocolate milk). So, seeing that it is Friday and I don't really feel like doing any of my own work, I put the only superpower that grad students posses (literature reviewing) to good use.

First of all I'd like to address the widely cited study that looked at the use of chocolate milk as a recovery drink

They had participants do an interval workout, have four hr recovery with one of three drinks then do an endurance trail to exhaustion. The three drinks were a fluid replacement, carb replacement or chocolate milk. They found that the participants time to exhaustion and total work was highest for the chocolate milk and fluid replacement vs the carb replacement. So this study showed that chocolate milk is a more effective recovery drink than a carb replenishment alone. This is no big surprise as it is widely accepted that in addition to carbs some protein is required for optimal recovery.

I also looked into the make up milk protein and the research on it's components with regards to exercise. Basically, there are two main components to milk protein: casein and whey, and they are found in a 80:20 ratio (casein:whey). The main difference between these two proteins are the speed of absorption and utilization. Whey protein contains high levels of branched-chain amino acids (BCAA) compared to casein. The big thing about BCAAs is that they can travel directly from the blood stream to the muscles whereas other protein must undergo degradation by the liver prior to being incorporated into the muscles. Additionally, caseins form globules (yes, globules) in your stomach and take longer to absorb. Whey protein intake results in a peak in blood amino acid levels at 40 in compared to 4-7 hrs for casein.

So to recap, milk has two forms of protein, one fast and one slow. It also turns out that there are two main protein synthesis pathways involved in muscle remodeling. Whenever you exercise, your muscles undergo remodeling requiring amino acid incorporation and protein synthesis. Basically, the one pathway relates to the production of structural proteins involved in muscle contraction and the other to the development of mitochondrial systems which are responsible for providing energy for muscle contractions. It has been shown that resistance based exercise tends to stimulate activity in the structural pathway whereas endurance based exercise tends to stimulate activity in the mitochondrial pathway. It has also been shown that these two pathways have different time courses such that the structural pathway is active earlier than the mitochondrial pathway.


So, what does this all mean with regards to cycling training (which is all we really care about after all). Well, when we are training (esp in our spinning classes) we are performing both resistance and endurance exercise. Therefore we will be engaging both the fast and the slow protein synthesis pathways. So following workouts, in order to maximize the benefits of the muscle remodeling that we have engaged we need to get both immediate as well as delayed protein sources. This can be provided either with a post exercise whey intake (in whatever form) and subsequent meal or with a combination of proteins sources.

Purely speculation now, but I suspect that post work muscle soreness may be due to insufficiently fueling the structural pathway whereas muscle fatigue may be due to insufficiently fueling the mitochondrial pathway (or insufficient glycogen recovery...but we'll save that for another post). So be your own judge, if you find that you are tired a couple hours or days after a hard workout, you may consider increasing your protein intake.

So if you find that chocolate milk works for you, and you are able to keep training day after day, go for it. But don't forget, regardless of what you have right after workouts (and you should have something) most of your daily nutritional needs are covered with a well balanced diet, so don't for get to have a meal after you get back from the gym.

And of course, this is not my field of expertise so if anyone has contradictory or complimentary information I would love to hear it.

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