Optimizing Muscle Growth – Exercise Selection
One of the most unique features of skeletal muscle is that its adaptation is stimulus specific. This concept holds true in both hypertrophy (muscle growth) and performance. Meaning, in contrast to body fat, where the exercise selection won’t necessarily change the physical outcome, in muscle it will.
You want more developed arms? Choosing movements that target the muscles through elbow flexion/extension will help grow them. Want to develop your hamstrings? Choosing movements that involve knee flexion will help do that.
This is the basis for bodybuilding. Using exercise to build and shape the body to create a physical appearance that best fulfills judging criteria based on your genetics.
As mentioned previously, this also carries over to performance. So, for those who don’t have body-image related goals, some of these concepts may still apply. But for the purpose of this blog, we will be discussing exercise selection in the context of hypertrophy.
If you haven’t read my introduction to resistance training eBook, check it out here. It will give you all the basic knowledge you need to tackle this article.
Frequency, Volume, Intensity
What is Training Frequency?
Frequency, for the sake of our discussion, is the number of sessions or workouts per week you perform exercise for the purpose of hypertrophy.
What is Training Volume?
Volume, for the sake of our discussion, is the number of challenging sets performed per muscle group per week. For strength athletes, this may also include a multiplier based on the amount of load used, but this is uncommon for hypertrophic goals.
What is Training Intensity?
Intensity, for the sake of our discussion, is the difficulty of each set. Intensity can be described in many ways, such as rate of perceived exertion (RPE), reps in reserve (RIR), or percentage of 1 rep max (%1RM). During hypertrophy training, usually volume is described by proximity to failure using RPE or RIR (see scale below).
What is optimal? Well… it depends.
There is constant debate in the science-based exercise community between what is the optimal training volume, frequency, and intensity for growth. There is good reason for this, the research is still on-going and the manipulation of all these variables depends on individual factors, such as training experience. I am going to step back from these topics in this discussion, but it’s important to be aware of them because they will impact your exercise selection.
Now stick with me here, I am going to run through why this can get so complicated...
Your training frequency depends on your volume. Someone who requires a lot of sets/week to stimulate growth will need to break them up. Here’s an example to help explain this:
If someone wants to accumulate 20 sets per week on a muscle group in one session, that 19th/20th set isn’t going to be very stimulatory because they will be fatigued from the 18 sets prior. Imagine how hard you’d be able to train those final 2 sets after all that.
However, if you split that into two 10-set-sessions, the 9th/10th set may be more stimulatory because they are less fatigued from only having 8 challenging sets prior. This is much less than our previous example of 18.
Your volume depends on your training intensity. Someone training at higher intensity may need less volume to stimulate as much growth. Your volume may also depend on your rest between sets, with more rest allowing for a higher training intensity, and therefore less volume.
All of this depends on your recovery. Recovering poorly might hinder your ability to add more volume, frequency, or intensity to your sessions. Doing so without improving recovery would quickly lead to overtraining.
Your recovery depends on the muscle being trained, with some saying smaller muscles are able to recover faster in specific contexts compared to larger muscles. But this has yet to be proven.
Your exercise selection depends on your intensity, volume, and frequency. You may want more compound movements that allow for multiple muscle groups to be trained within a shorter timeframe if you are limited on time.
See how this can get really complicated? All these factors depend on one another and overall, they depend on you. Your genetics, habits, recovery, training experience, etc. But this is why coaching is such an art; you experiment with variables based on an athlete's needs and capabilities.
*I have consistently trained at around 12-16 sets per week per muscle group, dedicating more to smaller muscles. That is my typical volume when optimizing for hypertrophy, split between 2 sessions. So, I train each muscle twice per week. I also try to keep my sets to around 15 sets per session. Because this is where I found fatigue doesn’t hinder my training capacity. But some will do better with more, and some will do better with less. Given these volume perimeters, I train around 5-6 days per week.*
Limiters and Stability
I am a huge supporter of functional training. Training balance, unique and challenging ranges of motion, and postures that replicate the motions of everyday life. But this holds no place during the working sets for optimizing hypertrophy.
Most of these movements increase what I am going to call neuromuscular distraction. This means in addition to carrying out the task at hand, your nervous system must also worry about other factors challenging the movement (read more). For example, think of a single leg deadlift verses a barbell Romanian deadlift. Because the base of support is so narrow in a single-legged deadlift, you must maintain balance first. This is the limiter of your force production. There is some great research done on this you can read here. But think about this for yourself, if you can Romanian deadlift 225, have you ever singled leg deadlifted more than 100lbs for the same number of reps?
So, for hypertrophic programming, it’s beneficial to stick with simplistic and stabilized movements to optimize your force production for your hypertrophic stimulus. Then including other movements for separate and complimentary benefits.
This applies to many more movements and can even go a step further away from free-weights and into machines. Like substituting a barbell back squat for a hack squat, a dumbbell press for a machine press, etc. Although the latter would theoretically provide much less of a difference because a dumbbell press is still a very stable exercise (especially with increased internal stability at higher body fat percentages), it is possibly still beneficial in some cases.
Neural Drive
Neural drive is the ability for your nervous system to use a muscle to produce force. This lowers as resistance training sessions are prolonged (read more).
Remember that the sets in the back end of a session will not be as stimulating as the initial sets. Well, this is due to neural drive and some other local factors within the muscle.
So, this provides us with a tool we can use when looking to preferentially stimulate growth in certain areas. Movements earlier in the workout could be more beneficial for promoting growth, so if we want a target tissue to grow or perform better over time, prioritizing it by placing it earlier in exercise sequence might be beneficial (source 1, source 2)
However, it’s easy to make mistakes here. You don’t want to limit your ability to perform subsequent movements in a session. For example, training a leg extension to failure before a squat may improve quad hypertrophy, but you are limiting the squat pattern by fatiguing your quads, dampening the stimulus for other muscles involved, like the glutes.
I do this by putting some of my lacking body parts earlier in my leg workout, such as my glute and calve work for example.
The Amount of Muscle being Used
The amount of muscle being used could play a role in how we help manage fatigue within our workout, so those final couple sets are just as stimulatory as the first. You can change the total amount of muscle you are using in a movement using two methods.
First, you can change the movement to include less joints. For example, changing a squat to a leg extension. Although having the obvious downsides of not training the glutes, the leg extension should be less fatiguing and use less musculature (read more).
Due to this concept, many include single joint exercise after their multi-joint exercise. This has been a practice since the early days of bodybuilding. But there is some research that seems to disprove this concept. For example, when looking at the addition of the hip thrust to a workout consisting of leg press and stiff-legged deadlift, there was no additional hypertrophic progress (source).
This could be due to the glutes already being fatigued from the stiff-legged deadlift, or the individuals training history. So, the concept isn’t disproven yet and still holds validity through experiential knowledge in bodybuilding circles. However, more research is needed.
The second method is by changing the movements to be unilateral. This is useful for the same reason as the first, as unilateral movements have been shown to create less central fatigue*.
*There is a difference between peripheral fatigue and central fatigue. If you’d like to learn more or create your own opinions, check out this study!
So, you could choose to perform unilateral movements near the end of the session to bypass some of the fatigue created by those earlier, bilateral movements. This could lead to more effective sets and therefore possibly more growth.
I hope this blog helps get you thinking about some training concepts when it comes to using exercise selection to optimize muscle growth. The research in this field is always on-going so if you have any of your own opinions, or suggestions for more reading on the topic, please leave it in the comments of this blog. Remember what is optimal and what is best for you are not always synonymous. Priority number one should be that you enjoy your workouts, or you’ll never do them.