Six people. One study. No practical outcomes. You drink protein before working out.
There is a neat research tool that I use a lot. It’s called the Web of Science. A lot of you use PubMed to find articles. You punch in a topic and it spits out a list of studies about that topic (roughly). Web of Science is a similar database, but it’s like a reverse lookup for studies. I punch in a study and Web of Science tells me about all the studies that have citied that study (i.e. have listed it in the references). This is an extremely useful tool when looking for follow-up studies.
We’ve already talked about very recent evidence about pre-workout protein and energy expenditure, so this week, I wanted to find the most recent evidence of using pre-workout protein for muscle growth, since that’s probably the REAL reason you’re drinking protein before a workout. While there are some studies that have looked at post-workout protein as well as both pre and post-workout protein, surprisingly, there haven’t been many studies on just pre-workout protein use and muscle growth.
The Tipton et al study of 2001 is one of the earliest and only studies on the use of pre-workout protein and muscle synthesis. It’s also the most widely used study in terms of justifying pre-workout protein. I’ll be getting into the guts of this study in this post, but what’s really interesting is that in the Web of Science, there haven’t been any studies that citied Tipton et al 2001 that have looked at pre-workout protein use alone since then. And if a researcher was going to look at pre-workout protein use (either alone or in combination with anything else), they would be very remiss in not including this study in their references.
So, where’s the beef? Apparently, this is it.
Tipton KD, Rasmussen BB, Miller SL et al. Timing of amino-acid-carbohydrate ingestion alters anabolic response of muscle to resistance exercise. American Journal of Physiology, Endocrinology and Metabolism 281:E197-E206, 2001.
We know that lifting weights causes muscles to grow more than they are broken down. We also know that putting amino acids intravenously into someone after lifting weights increases muscle growth more than putting amino acids into someone at rest. But the question in this study is whether ingesting amino acids before exercise increases muscle growth more than ingesting amino acids after exercise.
Six subjects were recruited for this study (3 men, 3 women). Average age, 30 years old (SD 3.1 years). They were “recreationally active” and otherwise healthy. One week before the experiment, they were all familiarized with the strength testing protocol as well as leg press and leg extensions.
The night before testing, subjects fasted from 2200h until about 0600h. The next day, which was the day of testing, the subjects had catheters inserted into the femoral artery and vein as well as an IVs in both arms. Blood samples were taken and then an infusion of radiolabelled phenylalanine was started through one of the arm IVs, and an infusion of indocyanine green was infused through the femoral artery.
After 2 hours of infusion, more blood samples were taken to determine the concentration of amino acids in the blood. Muscle biopsies were also taken at this time from vastus laterals to determine the concentration of amino acids in the muscle while the phenylalanine was being infused.
After the muscle biopsy, the subjects drank either a placebo drink, or a protein-carb drink. The protein-carb drink had about 5 grams of essential amino acids (including a bit of radiolabelled phenylalanine) and 35g of sucrose (table sugar). The placebo drink was just water with aspartame.
The subjects then did 10 sets of 8 reps of leg press at 80% of 1RM, and then 8 sets of 8 reps leg extensions at 80% of 1RM. The subjects had more blood taken after the 4th and 8th set of leg press and after the 2nd and 8th (or final, whichever came first) of leg extension). Another muscle biopsy was taken between the 7th and 8th set of leg extensions.
After all of this, the subjects drank either a placebo or a protein-carb beverage (whichever one they didn’t drink before). More blood was taken 10, 20, 30 45, 60, 90 and 120 minutes after exercise; and two more muscle biopsies were taken at 55 and 115 minutes after exercise.
Each subject did the whole over again, switching the order of the drinks at some later date.
[On a personal note, I cannot imagine going through all of this. Muscle biopsies hurt!]
Blood was analyzed for free amino acid concentration. Muscles were measured for free amino acid concentration. Calculations for amino acid uptake were made based on differences between arterial and venous blood samples, the rough theory being that nutrients are brought to the muscle through the artery and then the blood continues on its way with less amino acids in it. I won’t go into the calculations here.
Phenylalanine concentrations were compared using one-way ANOVAs for time. Differences between pre and post values were compared using t-tests (unadjusted for multiple comparisons). I stopped counting the number of tests after 20.
Phenylalanine concentrations were higher in the pre group at rest than the post group. The phenylalanine concentrations remained higher than the post group at all time points. However, after adjusting for the differences at rest, these differences essentially became inconsequential.
In the muscle biopsies, the pre group had an uptake of 180mg (SD 50mg) of phenylalanine, while the post-group had an uptake of 39mg (SD18mg) of phenylalanine over the 3 hours of the study. This was found to be statistically significant, but this difference only seemed to be preserved if you tested for the entire 3 hours. When tested for only the last 2 hours, the pre group had an uptake of 195mg (SD 37mg) while the post group had an uptake of 130mg (SD 45mg).
[The reason why uptake is more over 2 hours than it is 3 hours probably has more to do with protein breakdown which was factored into the calculations.]
So, what exactly does all of this mean?
Well, this study does show an increase of phenylalanine uptake with 5g of protein and 35g of sugar in muscle. There only one problem. Phenylalanine isn’t metabolized in muscle cells. This study assumes that all other amino acids (including the ones that your muscles DO metabolize) are taken up as at least as well as phenylalanine (which, on the whole is probably not unreasonable). But it’s a bit more of a leap of faith to take to assume that just because the amino acid is taken up by the muscle, that it is actually USED. And despite the intuitive idea that more amino acid uptake might imply increased protein synthesis, we have already seen in at least one other study, how producing “significantly” higher levels of something doesn’t necessarily result in a change in the factor that we’re ACTUALLY interested in: namely muscle growth.
We also don’t know what happens beyond the 3-hour testing time frame. Does the supposed increased uptake AND metabolism actually result in bigger muscles? How much bigger? Over what time? And how generalizable are these results to the rest of us, given that only six people were actually studied?
So many unanswered questions, yet this is the level of research evidence upon which the recommendation to drink (or eat, but mostly drink probably) protein before your workouts to increase muscle mass is based. Yes, the recommendation in the fitness magazine. Seems pretty flimsy, eh?
This isn’t to say that this is a bad study, because it’s not. It answers the question it set out to answer. What’s bad is that the recommendation YOU’VE received as a result is based on a single experiment (that I could find at any rate) on six people, using a test that doesn’t directly measure protein synthesis and cannot make statements about whether the alleged increase in protein uptake actually results in larger “protein accretion”, as the authors call it (or, in plainspeak, “bigger muscles”.) I haven’t found any other study to support this strategy. If you know of a study that has looked at actual muscle growth (and not a surrogate indicator), and pre-workout protein, let me know!