For decades we’ve known that to get big and strong, you have to lift heavy things multiple times, relatively frequently. However, only recently have sports scientists begun to uncover what is taking place at the cellular level that drives muscle growth.
Suffice it to say we are in the midst of a “golden era” for exercise science, particularly in regards to muscle hypertrophy, as scores of studies have been published in recent years investigating the ins and outs of muscle growth and human performance. From this constant research effort, scientists have identified three main mechanisms of muscle hypertrophy1 as:
• Mechanical tension (i.e., weight on the bar)
• Muscle damage
• Metabolic stress
However, a new systematic review indicates that cellular swelling may be a much more powerful driver of muscle growth than previously thought. Before we get into the study and its findings, let’s quickly review what happens when you get a muscle pump.
HOW DO MUSCLE PUMPS WORK?
During resistance training, arterial blood flow to the working muscles increases while muscle contractions cause compression of veins. This creates a scenario similar to turning a faucet on high, and attaching balloon to it that has pinhole on the end. The water will rush in, and since the exit (hole) is so small, the balloon continues to fill, getting bigger and bigger.
The same thing happens in your muscles. More and more blood flow is being pumped to the muscle, yet due to repeated muscle contractions, the “exit” (veins) is restricted, creating a “pooling” of blood in the muscle along with tremendous cellular swelling and one hell of a muscle pump. The body perceives this sudden swelling as a threat to the structural integrity of the cell and its survival. In response to this threat, the cell enacts various anabolic processes (including upregulation of protein synthesis) while simultaneous downregulating catabolic processes occur to make a bigger, stronger, more resilient muscle cell.2
So, maybe all those gym bros who were chasing the pump for years and years in the gym were onto something?
Still, the common belief among researchers was that cellular swelling and various other metabolic stress factors weren’t directly responsible for muscle growth. They were either “permissive” of anabolism or a “secondary” factor due to performing greater amounts of mechanical work, with the thinking being that lifting heavier weight (increased mechanical tension) would lead to higher levels of metabolites.3 However, recent studies suggest that cellular swelling and metabolites may be an independent factor of muscle hypertrophy, not merely a supporting cast member or by-product of heavy lifting.4 A new review published in Nutrition set out to investigate the role various cell-swelling supplements have on muscle growth.5
3 WAYS TO INCREASE CELLULAR SWELLING AND GET A MUSCLE PUMP
Over the years, scientists and supplement companies alike have searched for compounds that are capable of enhancing exercise-induced hyperemia— “the pump.” As you’ve probably seen, there’s no shortage of ingredients and full-blown pump pre-workouts from which to choose. But, not all products are created the same, nor do they all work via the same pathways. In fact, researchers have identified three main mechanisms by which sports supplements enhance cellular swelling:
• Vasodilators, such as nitric oxide boosters.
• Anaerobic energy system ergogenic aids that increase metabolite production, such as beta-alanine and creatine.
• Osmolytes, such as creatine and betaine. Let’s take a deeper look into each of these categories to see how they impact cellular swelling, and potentially muscle growth.
Vasodilation refers to the opening or widening of blood vessels, which leads to an increase in blood flow and decrease in blood pressure. A number of compounds, termed vasodilators, have been investigated over the years that promote this expansion of blood vessels and increase in blood flow. These blood flow-boosting agents are highly sought after by the medical communityfor their role in promoting cardiovascular health and treatment/prevention of hypertension, while the lifting communityis primarily interested in their ability to yield massive muscle pumps.
Vasodilators work primarily by increasing nitric oxide in the body, but they can also work by counteracting the vasoconstrictive actions of certain enzymes in the body, such as angiotens in-converting enzyme (ACE).
Now, in regard to boosting nitric oxide, supplements accomplish this via one of two distinct NOS (nitric oxide synthase) pathways in the body— the NOS-dependent pathway or the NOS-independent pathway.
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