Stuck at home without access to weights, my attempts at continued muscular hypertrophy seem restricted since I can’t effectively use the common method of increasing the weight I’m lifting as a means of adding unaccustomed stress to my body, forcing it to respond by growing. A history lesson:
Milo of Croton was a legendary wrestler and all around strongman in ancient Greece who allegedly carried a bull around on his back. He started carrying the bull when it was just a calf and continued carrying it as it grew. As a result, Milo also grew giving rise to the concept of progressive overload, i.e. lifting more and more weight, as a means of muscular hypertrophy.
Fast forward a bit and the pursuit of muscle growth also grew, but still mostly as an underground niche activity. It was theorized by its practitioners that growth came from three methods: mechanical tension, muscle damage, and metabolic stress. Training routines were built around ensuring all three aspects were incorporated.
Fast forward some more, and the pursuit of muscle growth became more mainstream until an entire industry was created. There was very little in the way of actual scientific evidence to support the myths and lore about how hypertrophy actually happened, but eventually people started testing some of these concepts.
Today, it is fairly well established that mechanical tension is the mechanism by which muscles grow. Muscle damage is actually a determinant to growth, which I’ll explain shortly. Metabolic stress may contribute some, but without mechanical tension hypertrophy wouldn’t happen. Many people still persist with the old school idea that all three methods produce hypertrophy, but some well constructed studies have shown that is not the case.
What we know is that when the brain receives a signal that a muscle needs to activate to complete some kind of movement around a joint, like bending your arm at the elbow, it sends electrical impulses to the motor units controlling the muscle fibers and signals to them to contract. Staying with the arm bending as it’s an easy muscle to visualize, the bicep muscle is responsible for bending the arm. The brain activates just enough muscle fibers to get the job done. No growth is triggered by this movement because the body has already grown the muscle it needs to conduct basic movements under gravity. But what if the arm encounters more resistance than it normally does when it bends under the day to day living conditions to which it has already adapted? Let’s put a dumbbell in that hand and then bend the elbow. The brain activates more muscle fibers–there are thousands of them in the body–so it can get the job done. If you keep lifting the weight repeatedly, the muscle fibers start fatiguing. The brain now contacts what are called high threshold motor units that control bundles of many muscle fibers and they all kick in to help. They will also fatigue eventually from all this contracting until the arm struggles to continue to complete the movement.
The fibers actually bulge and deform when they contract under this mechanical tension, and as a result of this purely mechanical action, a chemical reaction is triggered. Muscle protein synthesis is turned on and new proteins are added to the fatigued and deformed fibers and as a result, they will be slightly larger than they were before. This process can take up to 72 hours if it’s a new experience for your body, but if you keep doing this with some regularity, the time of increased protein synthesis can decrease to 24 hours. This is called the repeated bout effect, which means your body is now accustomed to this new activity so each subsequent activity creates less of a stress, and as a result, there’s less deformity and less accretion of new proteins.
The muscles won’t grow indefinitely, and we don’t know exactly what the limiting factor is, but it’s likely myostatin. Mysotatin is a protein created by the body that actually restrains muscle growth, and the less one’s body produces, the more muscle mass they will carry naturally.
The most common method to keep adding more stress to the muscle is to try to lift more weight than the last time you did a particular exercise. The idea being that more weight will add more stress to the muscles that have now adapted to the weight you moved last time. But what if that’s not exactly right?
Consider again that what creates hypertrophy is the chemical reaction from mechanical tension which increases muscle protein synthesis and the accretion of new proteins on the individual muscle fibers that bulged and deformed when contracting under strain. As fibers fatigue, more fibers are recruited until they also fatigue. Why would it require more resistance to get to the fatigued state? It may take more repetitions before fatigue is reached, but we will get there.
Studies have shown that when taking a set of an exercise to temporary muscle failure, i.e. until all the fibers are too fatigued to continue, the same amount of muscle growth results from loads as light as 30 repetitions to temporary failure as heavy sets of only 3 repetitions. The heavy sets engage all the muscle fibers basically right from the start of the set, where as the lighter loads take some time to fatigue fibers and engage those bundles of fibers controlled by the high threshold motor units.
So here’s my hypothesis: I should be able to create enough mechanical tension to create the chemical process that causes new proteins to be added to the fibers by taking each set to temporary muscle failure, even if it’s the same weight I used last time and the time before that. It may take more repetitions to get there, and it should if my body is adapting to the work I’m doing, but there’s no reason I can think of that the body wouldn’t respond to the same process. If I do push-ups for example, my chest, front deltoid and triceps muscles will be engaged by the brain to activate and complete the movement. If I were to stop the set of push-ups well short of temporary failure, one could see how there would be little new growth because many of the muscle fibers were never activated. Remember the high threshold motor units don’t get the call to action until the initial muscle fibers fatigue under the workload.
I’d love to be able to properly test my hypothesis, but it’s just me and I don’t have the means to do muscle biopsies or blood work to see the muscle protein synthesis. I don’t have another person to do the same workout but adding weight every time to see which of us grows better. But I think the evidence supports the hypothesis and while I may not get a lot of growth because for all I know, I’ve hit my limit based on what my DNA will allow, there are over 600 muscles in the body, each with thousands or maybe even tens of thousands of individual fibers. Chances are, there are some fibers in there that haven’t been stimulated to their maximum extent. So I’m not going to sweat the inability to add more weight while I’m stuck training at home and just focus instead on taking each set as close to failure as I can.
Before I close, let’s visit muscle damage as a component of hypertrophy and why it’s actually not a factor in growth, and actually detrimental to the process. It was once theorized that lifting weights caused microtrauma to the muscles, small tears that required repair and thus, a larger and stronger muscle. It sounds reasonable, but what we’ve found is that when actual damage occurs, the muscle protein synthesis that adds new proteins to the fibers is actually detoured to repair the damage which the body views as an injury. Instead of adding proteins to the bulged and deformed fibers that were stimulated by the mechanical tension, our body uses the increased protein synthesis to treat the injury, leaving nothing for the hypertrophy of the non-injured fibers. Muscle damage takes longer to heal than just adding proteins to the stimulated fibers, so recovery is delayed and you can’t train again as soon as you could have without the damage. If you insist, you’re headed toward a more significant injury which will sideline your ability to train. Many so called “advanced techniques” like forced reps and heavy eccentrics, where you lower a weight heavier than you lift, cause the damage we want to avoid.
There is one thing that makes training in this way challenging. There’s an energy component to short term exercise as our body has to make ATP to fuel the muscle contractions and ATP runs out pretty quickly. Higher repetitions create the metabolic stress we once thought added to hypertrophy, but what it actually does is create a temporary sensation of fatigue; a kind of burning in the muscles, that combined with the exhaustion of ATP makes continuing the set very difficult. This doesn’t really happen with aerobic activity because the body uses a different energy system to fuel that activity. Imagine going for a long walk. You can probably walk for hours before you ran out of fuel. In fact, you’d likely have structural or nervous system fatigue before you ran out of actual energy to keep walking. But imagine trying to do push-ups for hours. Can’t be done. So it’s at least possible that I won’t be able to stimulate all those fibers I’m trying to get at because I have to do so many reps to fatigue enough fibers that I run out of energy or build up so much metabolic stress that I have to end the set before getting the most out of all the fibers. This is the beauty of being able to add more weight to the bar. You can keep the repetitions in a range that won’t exhaust ATP, or build up too much metabolic stress. But I’ll worry about that when I can do 4 sets of 30 push-ups or more. Maybe by then I’ll feel like I can go to the gym again. Doubt it, but one can dream.
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