A Decision Making Algorithm For Muscle Hypertrophy
This article is a companion piece to my previous articles titled, Hypertrophy: Adaptation Mechanisms & Training Guidelines and Individualizing Volume & Intensity For Hypertrophy Training. Collectively, these two articles discuss the mechanistic basis of muscle hypertrophy, general training guidelines for eliciting hypertrophy, as well as best practices for individualizing training. After publishing these articles I was sent the following question:
”How do you elicit growth in stubborn muscle groups? I sleep nine hours a night, am in a caloric surplus, and have been good training progress in all major muscle groups aside from my biceps. Do you have any recommendations aside from just doing more volume?”
The last sentence in this question is key. Often when someone has a lagging muscle group that won’t grow the approach they take is to increase total weekly set volume. While that can be an effective approach, it is not the only option and oftentimes it’s surely the wrong option. Below you’ll find a decision making algorithm for driving muscle hypertrophy in a lagging muscle group — i’ve traded nuance for ease of interpretation and application. However, my hope is that the remainder of this article serves to parse out all of the underlying principles that went into creating this model, so you can effectively troubleshoot issues using it as a guide.
Are You Recruiting The Target Muscle Effectively?
One of the surest signs that someone is not recruiting a target muscle effectively is that they maintain a high muscle oxygen saturation level in that muscle, even when pushing a work set to failure. For example, in the image below we have a NIRS trend captured from two different athletes performing a high incline dumbbell hammer curl to failure with the NIRS sensor on their brachialis. Note that athlete ‘A’ (red trend line) desaturates the biceps brachialis down to ~15% muscle oxygen saturation at the nadir, while athlete ‘B’ (blue trend line) has a minimum muscle oxygen saturation level of ~45% in the target muscle.
There are a few things that come to mind when I see trends like the one above for athelte ‘B’. The list includes the following:
Pre-position;
Exercise selection;
Movement Execution; and
Metabolic activity / Recruitment.
Starting with coordination, we need to look at the position of the axial and appendicular skeleton to see if there are any major postural faults. For example, if an individual is stuck in thoracic flexion and shoulder internal rotation they’re not going to be in an advantageous position to load the biceps. Before worrying about the nuances of exercise selection, volume, and intensity we first need to improve their position. Then once they are able to get into the proper pre-position, we can consider the specific movements they are using to train the target muscle. Some movements lend themselves better to creating high levels of mechanical tension while others lend themselves better to creating higher metabolic stress. Often times individuals select movements based on how much of a stretch they feel while performing it. However, as my friend Kassem Hanson of N1 has pointed out, that doesn’t mean it’s actually an effective movement. Additionally, it’s worth considering whether the target muscle is being loading in the shortened position, mid-range position, or lengthened position. If all of your training is being done with movements that load the muscle in the mid-range (which is a common occurrence) you may be missing out. If you want to learn more about exercise selection I highly recommend the Coach Kassem’s content over at N1 Training & Education.
Now, assuming that an individual has dialed in their pre-position and exercise selection, the next factor i’d look into is exercise execution. Often times simple changes in hand / wrist / elbow position during a biceps curl can make all the difference, as can specific tactile cues. For example, if an athlete has trouble feeling their biceps i’ll often make the following recommendations:
Minimize movement at the should joint and aim for full elbow flexion and extension while keeping the elbows themselves in a fixed position through the full range of motion.
Imagine trying to crush an imaginary pencil placed on the inside of the elbow joint at the top of each rep. You should aim to touch your forearm to your bicep and if you’re performing a supinated curl you can squeeze your pinky finger towards the should of the same same.
Control the eccentric, then lightly contact the triceps at the bottom of the eccentric.
Finally, if all else fails and the individual is doing everything right, but still cannot desaturate the target muscle i’ll do a thermography screen to see if there are any underlying tissue pathologies. The picture below depicts sample thermograms taken from an athlete recovering from a left ACL injury and aright achilles tendon injury.
A thermogram is a representation of heat radiating from the body. Skin temperature regulation is impacted by blood flow, muscle recruitment pattern, inflammation, and injury. Despite the fact that our bodies are thermally balanced, injuries injuries can cause thermal asymmetries. As a result, infrared thermography allows one to detect these thermal asymmetries, which represent regions of interest related to tissue pathologies, faulty biomechanics, or changes in tissue perfusion. In the image above you’ll see cases where an individual has a hypothermic asymmetry caused by decreased metabolic activity in the tissue. In these scenarios individuals will often have atrophy in the surrounding tissues, and will often note that they can’t get a ‘pump’ in those muscles. In order to hypertrophy these tissues normal function first needs to be restored.
Are You Training With Sufficient Intensity?
If you want to boil water on the stove, you would never put the flame on the lowest setting - the water would never reach a rolling boil no matter how much time you gave it. Instead, you would set the flame to the appropriate intensity and then lend it the proper time it needs to make the water boil. The same concept applies to hypertrophy training - if you’re not training with the requisite intensity, it doesn’t matter how much volume you’re accumulating over time. You’re not going to make improvements.
The first component of intensity is loading. Based on the current body of research it looks like a set performed with thirty percent of an individual's maximum voluntary contraction or one repetition maximum provides the same stimulus for muscle growth as a set performed with ninety percent, assuming both sets are taken to volitional failure. This has been demonstrated by Jenkins and colleagues in their 2015 paper titled, Neuromuscular Adaptations After Two and Four Weeks of 80% Versus 30% 1RM Resistance Training to Failure, as well as by Schoenfeld and colleagues in their 2015 paper titled, Effects of Low vs. High-Load Resistance Training on Muscle Strength and Hypertrophy In Well-Trained Men. If we can still drive hypertrophy with as little as thirty percent of one’s one repetition maximum, can we do it with ten percent? Where is the low end cut off point? In a study by Lasevicius and colleagues titled, Effects of Different Intensities of Resistance Training With Equatted Volume Load on Muscle Strength and Hypertrophy, the investigators sought to answer this question. Based on their findings we can infer that the low end cut off for muscle hypertrophy occurs between twenty to thirty percent on an individual's one repetition maximum, though I'd wager that it may be higher than thirty percent for select individuals who were underrepresented in this study. The crux for any athlete wishing to achieve a meaningful degree of muscle hypertrophy is figuring out where their cut off points are so they can train with greater specificity. If the number of hard work sets you can do for a given muscle group per week are limited, as they are for any individual, then it’s crucial that all works sets be performed in an intensity range where an individual is capable of desaturating a tissue, increasing motor unit recruitment, and eliciting hypertrophy. Personally, I recommend exercisers err closer to ~40-85% of maximum voluntary contraction for practical and logistic reasons, with the bulk of training being done within the upper two-thirds of that loading range. The second component of intensity is proximity to failure. I tend to advocate for 1-2 reps in reserve (RIR) on work sets for most individuals. However, people often underestimate their proximity to failure, so it can be worth having lower training age athletes push to failure every so often on exercises where it is safe to do so as a means of calibrating their efforts.
Are You Training With Enough Volume?
An S-shaped curve depicts the relationship between total weekly training volume (defined as sets performed within an effective loading range taken within close proximity to failure) and the rate of muscle hypertrophy. If you perform too little stimulative volume for a given muscle group, the rate of muscle growth will be very slow. The lowest volume threshold needed to produce a result is often termed the minimum effective volume (MEV). Then as you increase volume, the rate of muscle hypertrophy will increase, up until a point where additional volume yields diminishing returns. This threshold is often referred to as maximum adaptive volume (MAV). Finally, there will be a point where even more volume provides little additional gain and where crossing it becomes maladaptive. That threshold is often referred to as the maximum recoverable volume (MRV). The goal is to determine what range of work sets correspond to each of these thresholds for a given muscle group. These ranges differ substantially from person to person and from muscle to muscle within a given individual. A good starting point for beginners and early stage intermediates can be 10 sets per week per muscle group for a given individual. For late stage intermediates or advanced athletes 15-20 sets per muscle per week may be more appropriate. These ranges often approximate MEV for many athletes and is unlikely to be within striking range of MRV, so they a safe starting points. However, hard gainers' MEV’s are often much higher. If the primary goal is muscle growth, we’ll also typically want to work within volume ranges on the right end of the s-curve closer to MAV.
Are You Managing Frequency Properly?
Suppose an individual uses proper exercise selection, executes movements correctly, and performs all of their training within an effective loading range. In that case, the total number of work sets taken to near failure for a specific muscle group is likely the greatest determiner for building muscle. However, as volumes get higher, it appears that we need to drive frequency up to see gains or even prevent a backslide from occurring. Based on the current body of evidence, it seems that the most productive sets you can do in a session for a given body part range from eight to fourteen sets on average. The exact optimal volume in a session is likely a product of the proximity to failure for each work set, the specifics of the training plan, the muscle group being trained, and individual factors like recovery, genetics, work capacity, physiological predisposition. For example, suppose you’re only doing ten sets of bicep training per week. In that case, you’re probably fine doing all of your volume in a single session, though splitting it up into two sessions may allow for higher training quality and subsequently greater gains. But, if you’re performing twenty sets of biceps training per week, it is ill-advised to do all of that in one session, and you’d probably fare better spreading that out over two to three sessions.
It makes intuitive sense that you can only stimulate so much muscle growth, or any other adaptation, within a single workout. Another reason why higher frequency may be desirable as training volume, defined as total work sets per week for a given muscle group, is that there is a limit to the amount of quality training you can do in one session. One of the more obvious reasons for this is that neuromuscular fatigue will accumulate across a workout, which will reduce muscle activation and, subsequently mechanical tension. Another reason is that we will accumulate more muscle damage with each set performed. Past a given point, each additional work set provides such little benefit that it is not worth the cost of being performed. If you keep pushing past that point, each set may not only provide little benefit but may actually be counterproductive as it may result in a negative protein balance, due to muscle protein breakdown, without stimulating more muscle growth or muscle protein synthesis. If this is done frequently enough over time, you may end up in a net negative protein balance, leading to losses in muscle mass.
The presence of a maximum productive training volume per workout would also explain why some studies find benefits of higher training frequencies, but others do not. Most of the studies that find benefits of higher training frequencies are in trained lifters with higher than average weekly training volumes. Conversely, there are many studies where training frequency does not seem to matter independent of training volume, and these studies are mainly done with training volumes below ten sets per week for a given muscle group.
The key to maximizing volume over an extended duration is all about walking the razors of ‘just enough’ before we start to see detriment, while simultaneously being able to drive progressive overload as a proxy for ensuring we’re getting muscle growth. Additionally, training volume should be optimized with training frequency in mind, not separately. Training volume should also be considered on a per-workout basis, not just on a total weekly basis. Training your chest two times per week with ten sets per session may have worse results than training three times per week with six to seven sets per session or even four sessions per week with five sets per session. That being said, when training with lower volumes, below twelve sets per week per muscle group, manipulating frequency doesn’t appear to be nearly as important as when training with fifteen to thirty sets per week for a given muscle group. The crux then becomes figuring out which of the above options are optimal.
Troubleshooting
What happens if you answered yes to all of the questions in the decision-making algorithm above but are still not growing the target muscle? The short answer is that you’re probably overlooking one of the components mentioned above. Maybe your exercise execution isn’t as optimal as you think it is, you’re leaving more reps in the tank each set than you think, you’re using too little (or too much) volume, or you’re not diving up your work sets throughout the week in a way that maximizes the quality of your training. All of those are possibilities. There is also the possibility that you are making improvements but just have unrealistic expectations of both the magnitude of change that will occur on short time scales and the length of time it takes to make a perceptible change to a given muscle.
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Great article again. Thank you Evan