In a previous blog post, I covered aerobic exercise and how essential amino acid (EAA) supplements can be used to mitigate the effects of muscle breakdown and improve performance. But what about combining EAA supplements and resistance training? Does that lead to any impressive benefits?
If you've spent any time in the company of individuals seeking to increase their physical strength and build muscle mass recently, you've likely heard them talking about branched-chain amino acid supplements (often referred to as BCAAs). They've become about as ubiquitous as whey protein! Proponents believe BCAAs can maximize muscle growth, decrease post-workout muscle soreness, enhance mental focus, and more. But recent studies indicate that when it comes to using amino acid supplements to enhance muscle protein synthesis (the building of muscle protein), there may be a much more effective option.
Before exploring the relationships between resistance exercise, amino acid supplements, and muscle protein turnover, let's get clear on some of the basic terminology.
Resistance Training, Defined
Resistance training can take many forms. You can lift weights to build muscles, or use the machines at the gym, or even use your own body weight in resistance exercises such as planks and pull-ups. If you're curious about resistance training but not sure where to begin, I recommend checking out this post.
Research links resistance exercise to a wealth of benefits, including better joint function, increased bone density, and enhanced muscle, tendon, and ligament strength.
To get the best results from any exercise program, including resistance training, it's vital to provide your body with the fuel it needs to power through workouts and recover in between sessions. Increasing muscle strength and mass requires close interaction between exercise and daily diet.
Protein is, hands down, the most important nutrient for anyone engaged in a regular resistance exercise training program. Protein contains amino acids, which are the building blocks of your muscle tissue. Even if you make sure to prioritize protein intake at every meal, you can still amplify your anabolic response via amino acid ingestion. In the most basic terms, taking amino acid supplements promotes muscle protein synthesis (sometimes abbreviated to MPS response) and can help your body build the most muscle in the shortest amount of time.
Understanding the Role of Amino Acids
In technical terms, amino acids can be defined as simple organic compounds that contain a carboxyl (-COOH) and an amino (-NH2) group. When these compounds link together, they form protein molecules. And it is those protein macromolecules that make up your muscles.
Your body needs 20 different amino acids to produce protein. Scientists categorized nine of these as essential amino acids.
Your body absolutely requires these nine amino acids not only to produce protein but also to carry out basic bodily functions that keep you alive. However, it cannot make them. Instead, they must be obtained from the food you eat. Anyone seeking to optimize her physical performance and muscle growth should review this list below outlining some of the important roles the essential amino acids play:
- Leucine: Many bodybuilders and athletes sing the praises of leucine supplementation—and for good reasons. One of the three branched-chain amino acids (BCAAs), leucine plays a significant role in muscle anabolism. It also activates mTORC1 (more on what that means later).
- Lysine: This amino acid contributes to muscle growth as well as tissue repair and nutrient uptake throughout the body. Lysine is the second most abundant protein found in human muscle tissue.
- Valine: Another of the three BCAAs, valine promotes muscle growth and tissue repair. Studies show that valine can have significant anabolic effects.
- Isoleucine: The third BCAA, isoleucine makes major contributions to hemoglobin synthesis as well as the regulation of energy and blood sugar levels. Isoleucine also speeds recovery, decreasing the time needed to repair post-exercise muscle damage.
- Threonine: Best known for keeping your muscles and connective tissues strong and limber, threonine also contributes to muscle protein synthesis. Plus, it can speed healing and help you bounce back faster from injuries.
- Phenylalanine: Adequate levels of phenylalanine are crucial for the structure and function of a vast number of proteins and enzymes. One of this amino acid's most notable functions is as a precursor to another amino acid, tyrosine, which your body converts into a number of brain chemicals including dopamine, epinephrine, and norepinephrine.
- Methionine: Your body needs methionine in order to carry out tissue repairs as well as to generate new tissue. Without methionine, the synthesis of protein cannot begin. Methionine also spurs the formation of collagen and cartilage.
- Histidine: Another of the amino acids involved in muscle anabolism, histidine combines with beta-alanine to form the dipeptide carnosine, which improves your performance during high-intensity exercise. Histidine is also involved in the synthesis of hemoglobin as well as tissue repair.
- Tryptophan: This amino acid maintains the balance between protein synthesis and breakdown in adults. And like phenylalanine, tryptophan is a precursor for important brain chemicals—in this case, serotonin and melatonin.
Amino Acids Flip the Switch for Muscle Growth
After you've considered the list of the ways the essential amino acids contribute to muscle protein turnover, you will hopefully have grasped a key fact: BCAAs are not the only amino acids involved in muscle growth and repair. So when it comes to amino acid supplementation for sports nutrition purposes, taking a BCAA supplement simply doesn't make sense.
Over the course of the 3 decades I have spent conducting NIH-funded research on muscle metabolism, I have garnered extensive data on how the muscles of the human body maintain themselves. The protein in your muscles continually break themselves down and rebuild themselves. In order to do this, they need a steady supply of all 20 of the amino acids involved in muscle protein turnover.
In order for muscle protein synthesis to begin, you must provide your body with one of the organic compounds that flip the "on switch." Research indicates that leucine, an EAA and BCAA, may just be the most potent activator of the MPS response.
As I mentioned above, leucine supplementation activates the mTORC1, or the mammalian target of rapamycin complex 1, thereby flipping the switch that turns on muscle protein synthesis. Scientists have found that leucine supplementation on its own requires a protein dose containing between 2.5 and 3 grams of protein in order to activate mTORC1. However, when individuals consume leucine in combination with the other eight essential amino acids, the required dose drops to 1.8 grams of leucine.
The mTORC1 pathway controls both anabolic and catabolic signaling of skeletal muscle mass, meaning it regulates both muscle growth and muscle tissue breakdown. Research has shown that pairing resistance exercise with essential amino acid supplementation has an additive effect when it comes to stimulating muscle protein synthesis via the mTORC1 pathway.
In other words, taking essential amino acids maximizes the hard work you put in during your training sessions and makes it easier for you to gain muscle.
How EAA Supplements Amplify the Benefits of Resistance Exercise
Resistance exercise stimulates muscle protein turnover. Muscle protein turnover is the balance between how much muscle protein is broken down and how much muscle protein is built back up. This is how muscle fiber function improves. Newer, better functioning fibers are synthesized to replace older ones that are not functioning as well. Both muscle protein breakdown and muscle protein synthesis are stimulated.
Since resistance exercise increases the efficiency of muscle protein synthesis, the increase in synthesis will be slightly greater than the increase in breakdown. The stimulation of protein synthesis is limited, however, because some of the essential amino acids released by protein breakdown are oxidized and not available to be reused for synthesis. Thus, even though the muscle is able to produce new protein more efficiently during resistance exercise, the balance between muscle protein synthesis and breakdown remains negative (i.e., net loss of muscle protein) in the absence of nutrient intake.
Therefore, performing resistance exercise in a fasted state does not result in a positive muscle protein balance. To tip the balance in favor of muscle building, you must consume essential amino acids to replace those oxidized while exercising.
If you’re simply looking to increase muscle strength, then you only need to consume EAAs. But, if increasing muscle strength and muscle mass is your goal, you need to eat extra calories in addition to EAAs. You can tailor your nutrition to your resistance-exercise goals—mass, strength, or both—by adjusting your EAA and extra calorie intake.
Together They Are Stronger
As I mentioned briefly earlier, there is an interactive effect between resistance exercise and EAAs. Both stimulate muscle protein synthesis, and the combined effect is greater than either of their individual effects.
Essentially, resistance exercise primes the muscle to produce protein at an accelerated rate, but muscle protein synthesis is limited by the availability of essential amino acids in the fasted state. With targeted supplement support, you can go from fasted to full of free essential amino acids ready and waiting to be put to use. The ingested EAAs are rapidly consumed by the muscle, in part because blood flow to muscle is increased by resistance exercise, and in part because the molecular mechanisms in the muscle cells that regulate the rate of synthesis are turned on. The net result is that the major gain in muscle mass that occurs after resistance exercise is due to the combined effects of exercise and the increased availability of EAAs.
In my research, I have found that when EAAs were given before resistance exercise, muscle protein synthesis was stimulated more than when given after exercise, but the EAAs given after exercise still caused a significant stimulation.
When Do I Take My EAA Supplements?
Unlike EAA supplementation for aerobic training, EAA supplementation during resistance training necessitates a before, during, and after approach that is customized according to your muscle and strength-building aims.
If an EAA supplement is ingested 30 minutes before resistance exercise, the muscle is put into a very anabolic state (where it is building up). If EAAs are consumed immediately after exercise there is also a stimulation of net muscle protein synthesis, but less so than if given before the workout.
So, you’ll want to take EAAs before a resistance workout to prevent the net breakdown of muscle protein during the workout. During resistance exercise, there’s an increase in blood flow to the muscle, and this increase can help deliver the ingested amino acids directly to the muscle for absorption. By increasing the blood concentrations of EAAs, the concentration gradients force EAAs into the muscle cells instead of out. Without EAA supplementation, the EAAs are forced out of the muscle.
Consuming EAAs after the workout will further stimulate protein synthesis and prolong the muscle-building response. The optimal approach is to take EAAs before and after resistance workouts, and throughout if possible.