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Purpose Of The Study
The purpose of this study was to evaluate the difference between a moderate amount of protein intake vs. a high amount of protein in terms of improving recovery in response to resistance training. Further, this was done, while controlling for total energy and protein intake.
Additionally, previous research has revealed that improvements observed with a higher amount of protein may actually be beneficial due to nutrient timing - i.e. other findings of improved recovery from training at the hand of higher amounts of protein may have seen the results because protein was consumed around the workout, rather than simply because the total protein was higher.
That last point about nutrient timing is really important. So, most people talk about protein and generally agree that the most important factor of protein and growth is total protein intake. Essentially, if total protein throughout the day is high, then muscle growth or maintenance should be similar. By this logic, you could consume all your daily protein in the morning before training and you should expect to see similar growth.
However, and this is a big however; It's important to note that nutrient timing, while secondary to total protein, can still play a major role in growth, over a long period of time.
When you exercise, you upregulate processes in the body that optimize muscle building, such as protein synthesis and GLUT-4 translocation. When this occurs and nutrients (like all of the macros) are present, you have the greatest likelihood of improving muscle mass and ensuring those nutrients are shuttled to the muscle.
Thus, it's very likely that in this "heightened" state of muscle building in response to exercise, that the body may use nutrients more efficiently, resulting in improved recovery. Keep in mind, I'm not saying that nutrient timing is more important than total intake. What I'm saying is that it's relevant and could play an integral role in muscle growth.
Why Study This
There are so many different arguments about protein. Studies like this help us sift through the bullshit and find a real answer. Some people say you need upwards of 3 grams per lb. of bodyweight, while others like one of the authors of the study think you need more like 0.8 grams per lb. of body weight. Research like this helps us observe responses to different amounts of protein, allowing us to draw more concrete conclusions.
14, resistance trained individuals took part in this study. Inclusion criteria of this study included:
Upon completion of strength testing, ensuring that each subject met inclusion criteria, subjects were placed into 1 of 2 groups, based on total calorie and protein intakes. Total calories intakes were adjusted according to their baseline calorie intake to ensure that total calories were within a "maintenance calorie amount."
It's important to take note that even though protein amounts differed between groups, they still maintained a normal total calorie amount. If for instance, the high protein group simply increased protein on top of their maintenance calories, they would now be consuming many more calories than before, which would likely improve recovery and potentially increase muscle mass significantly.
If however, the moderate protein group reduced protein intake (which they did), but did so without adjusting total caloric intakes, they may have observed poorer recovery ability, confounding the results. By maintaining total calories, we can observe how differing protein amounts affects recovery, rather than attributing differences to total calories.
Subjects were placed into 1 of 2 groups, which were based on either a moderate amount of protein (1.8 g/kg/day) or a high amount of protein (2.9 g/kg/day), while maintaining other typical calorie amounts. This was a 10-day crossover design, meaning that each group completed each procedure (moderate and high protein amounts), with a washout period of 24 hours in between. Upon completion of that 24 hour mark, participants switched to the opposing protein procedure.
For a clearer picture, as a 205 lb. individual this is the amount of protein you would consume based on your assignment:
Training & Peri-Workout Nutrition
Participants were provided with a pre-workout beverage containing 0.4 g/kg of a whey protein concentrate/isolate mixture. For a 205 lb. individual, this would equate to around 37 grams of protein, per beverage, which is typical of a pre-workout protein beverage. However, the actual protein amount was reported to be closer to .32 g/kg, making the beverage contain closer to around 30 grams for a 205 lb. individual.
30 minutes after completing their pre-workout beverage, subjects underwent a strength and exercise assessment (workout). The training procedure was administered as follows:
Lastly, on days 8-10 of each 10 day period, subjects were assessed on muscle soreness using a 0-10 visual analogue scale (0 = none, 5 = noticeable, 7 = uncomfortable, 10 = severe). This, by the way, is when resistance training was completed.
In terms of performance (black and blue ovals), we can see that only for back squat in the moderate protein group was there a significant decrease in performance by day 3 on average. With bench press, we actually see a slight, yet nonsignificant increase in performance for the moderate protein group.
For a finding like this, this decrease in performance was observed for the high protein group as well, just non-significantly. Although as you can see, the difference between non-significant and significant isn't very much. However, it's really not surprising, regardless of the protein amount, that performance would decrease. You're taking a very impactful exercise, such as the squat, and completing this movements to failure, 3 times, 3 days in a row. I think just about anyone's performance in the squat would suffer.
Additionally, it's not really surprising that the change would be drastic for squats and not as much for bench and row. Just consider for a moment how taxing taking squats to failure is, vs taking a bent over row to failure. I think you get the picture.
However, when observing the other variables in the green box, we do see a fairly drastic difference in terms of feelings of muscle soreness onset and the feeling of being uncomfortable. Even though it's not significant, i'd say it's close to borderline significant. There was certainly a trend for decreased feelings of soreness with a higher amount of protein.
However, keep in mind that we're talking about almost a 100 gram difference here, and differences between measurements were by and large insignificant. But also, keep in mind this is an acute study, over the course of months or even years, it's possible those differences become very significant.
The researchers tested for levels of creatine kinase, which is a metabolite that is indicative of muscle damage. As you can see, CK levels were significantly increased each subsequent trial and were not different based on protein intake.
Muscle damage is an interesting concept. In grad school, I had a professor named Carlos that brought up the idea of the repeated bout effect. This theory in essence postulates that muscle damage really only occurs when presented with novelty, or exercises / exercise sets/reps that you aren't used to or when you're a beginner. Otherwise, muscle damage probably doesn't play the role that many people think it does. In fact, I wrote an article on this very same subject here.
So essentially, we see this increase in muscle damage arguably because taking squats or any other exercise to failure using 80% 1RM for 3 sets, 3 days in a row, would increase muscle damage in almost every one. So, while we don't see differences here between protein groups, it's probably not because of the protein amount, but rather that muscle damage was going to happen, regardless.
Basically: 1. It's difficult to state that muscle damage is even extremely relevant and 2. Is this relevant for normal training, where high amounts of muscle damage probably won't happen to the extent we see here. I'm hypothesizing that we don't see a difference here simply because the stimulus causing the damage is too intense. I.E. No amount of calories or protein for that matter, would inhibit the muscle damage brought on by this training protocol.
Lastly, the researchers tested something called Phase Angle. This is essentially an electrical test that tests cellular membrane integrity. If this amount decreases, as observed with the moderate protein group, that's a potential indicator of damaged cellular membrane integrity or muscle damage.
This Was Short Term
It's important to remember that this test was short term. While increasing or at least maintaining adequate amounts of protein are suggested, it's unknown how this will play out long term. Based on the findings, it seems reasonable that consuming a moderate amount of protein (around .8 to 1 gram per lb.) is adequate when compared to a higher amount of protein.
Additionally, we did observe at least a tendency for higher amounts of protein being beneficial. But again, this is during a training protocol that likely elicited more muscle damage and thus soreness / decreased performance than we would probably normally see (due to the repeated bout effect).
Essentially, it's hard to determine if a moderate amount of protein performs the same as high amounts of protein, when the time frame is extended and people are exercising under the demands of a normal routine. Based on this study, for normal every day training, 0.8 grams per pound is likely adequate. Further, if training intensity or requirements drastically increases over a short period of time, it may be beneficial to increase that amount of protein, accordingly.
Protein Requirements Aren't An Exact Science
Consider two theories behind muscle growth. 1. Increasing protein synthesis frequently over time is arguably the leading theory behind muscle growth. 2. The other part of that theory is protein turnover, or the ratio of protein breakdown to synthesis. I.E. If the amount of protein you're synthesizing is greater than the protein being broken down, you should theoretically increase muscle mass.
The point of all this research is to 1. Find the optimal amount of protein to consume daily and 2. Find the minimum effective amount. Essentially, why would you want to consume 400 grams of protein if you could maximize the response at 100 grams, right?
The problem is, it's hard to tell from individual to individual what's the optimal amount of protein or even the minimum requirement. Is this number based solely on lean mass? What about style of training? What about frequency of training?
Literally, any variable could contribute to effective protein synthesis or ineffective protein synthesis. This higher recommendation amount however, is essentially to give a cushion. To.. provide a little bit of leeway to ensure that your protein synthesis rate is higher than that of protein breakdown.
So, do you need 4 grams of protein per pound of body weight for growth? Probably not. Can you get away with .8 grams per pound? Possibly.
This research suggested that, but there was a strong tendency for superiority of a higher protein intake. It's hard to know if say, the exercise protocol was increased by two days, would those tendencies become significant?
Personally, I'd say the observations in this study displayed the low end of plausible protein intakes; the minimum effective dosage if you will. However, i'd suggest erring on the side of caution and consuming closer to 1 gram per pound of body mass. Really, the difference there isn't large, but it provides a bit of leeway over that of .8 grams / lb. Not to mention, there are additional benefits of consuming higher amounts of protein, such as improved ability to control appetite. Remember that protein provides benefit outside of just building muscle.
Disclaimer: I have not read all of the current data with regards to protein intakes, but have read some. These suggestions are an extrapolation based on the information herein and should be taken as such.
Why This Should Matter To You
It matters because it adds additional information to the "protein requirement" argument. Many people throw around protein recommendations without actually understanding why that amount is being suggested. Further, this information provides what is probably the minimum effective dosage of protein, at least giving you an initial starting point, allowing for manipulation based on your individual response.