"During hypertrophy, contractile elements enlarge and the extracellular matrix expands to support growth" ref.
Short answer
Lift weights that get heavier and heavier over time.
As long as you lift heavier weights over time and avoid injuries, your muscles will get bigger.
We will cover the longer answer in detail in this post.
Muscle structure
In order to understand the underlying mechanism of hypertrophy, we need to go over a few anatomical terms.
Your muscles are made up of cells called muscle fibres. Each muscle fibre is made up of filament-like structures called myofibrils. A myofibril is made of contractile elements called sarcomeres, which contain actin and myosine. Actin and myosine "pull" on each other to create a muscular contraction. Look at the last sketch in the second image below to get a visual representation of this.
In this picture you can see how the muscle fibers make up the muscles.
In the picture below you can see what muscle fibers are made of.
Muscle growth happens when we increase the size and the amount of sarcomeres. This makes each structure above it larger. Bigger actin and myosin = bigger sarcomeres = bigger myofibrils = bigger muscle fiber = bigger muscle.
Sarcomeres are added beside each other. By adding more and more sarcomeres side by side, you end up with a larger muscle.
When you look at the image below, adding more sarcomeres side by side means increasing the amount of black dots. Eventually, this process would make the whole muscle fiber bigger.
what causes muscles to grow?
There are three main ways to start muscle growth:
1. Mechanical tension
Whenever you move a muscle, it creates tension within it. When you pick up your cup of coffee, there is a little tension, when you lift a 30 lbs dumbbell, there is a lot more tension. When you lift that dumbbell over and over during a set, you create a lot of tension.
Being able to safely create a high quality mechanical tension on your muscles is, in my opinion, the best way to induce hypertrophy. High quality means that the targeted muscle is doing most of the work and that auxiliary muscles are not taking over.
If you bench press too heavy and your whole body starts squirming to lift the bar back up, that's not quality.
The higher the tension, the more adaptation you get from your muscles, so lifting heavy weights is a good idea in this context.
In order to overcome the tension, your muscles will adapt by getting bigger.
2. Muscle damage
When you apply mechanical tension to your muscles, you literally break some sarcomeres. When these sarcomeres get repaired, they get beefed up a little more so they can handle that tension better in the future.
Note that mechanical tension and muscle damage are intertwined together. You could create muscle damage with less tension by doing more volume, but would that be as effective as creating damage with a higher tension workout?
That question deserves a post for itself and I will do one soon.
3. Metabolic stress
This refers to the build up of substrate (lactate, hydrogen ions, creatine...) that results from intense bouts of exercise lasting from 10 seconds to 3 minutes.
The actual effect of metabolic stress on hypertrophy is that it creates an environment in your muscles that stimulates hormones that promote for muscle growth.
This is the reason why doing "finishers" at the end of your workouts is good. A good finisher is relatively short, very intense, and gives your body that little extra incentive to adapt better.
That's also the main reason for muscle growth during HIIT workouts.
Tying it all together, how to workout for muscle growth
What to focus on during your workout
Given what we learned about the three causes of growth, your workouts should focus on two things:
High quality reps to create quality tension. Higher tension leads to more adaptation, so heavier weights are better for this. I do not recommend going to failure very often as that will compromise the intensity throughout the workout. Let's say you do 3 sets of heavy bench press. You gave it your all on all three and feel totally whipped out. You then decide to do dips. How heavy can you actually go on the dips after doing all that bench pressing? This is what I mean by high quality reps. If you can usually do 10 dips, but now can only do 6 because your chest and shoulders are tired from benching, the quality of those sets is lower than usual.
If you have time and if your weekly recovery is good enough, add in a finisher at the end of the workout. This could be a giant set, a drop set, or whatever other evil invention comes to your mind. Lighter weights are better for this.
Lifting weights at an intensity greater than 65% of your one rep max for sets of 2-12 reps is the most efficient way to gain new muscle. Longer rest periods (3-5 min) will allow you to lift heavier weights through your workouts and thus place more mechanical tension on your muscles.
When your muscles adapt enough to overcome a stimulus, it will stop growing over time. Imagine you do 3 sets of 10 push ups one day. You are sore for 2 or 3 days. Then the next time you do 3 sets of 10 push ups, you are only sore for one day. The third time you do 3 sets of 10 push ups, your muscles have fully adapted to that demand and you are not sore at all.
If you keep doing only 3 sets of 10 push ups, your muscles will not adapt further. You need to either increase your sets or your reps. Either do 4 sets of 10 push ups or 3 sets of 15 push ups to keep your muscle adapting. This is a simplification of the progressive over load principle.
Progressive overload
This is the process of continually placing greater and greater demands safely on your muscles. Progressive overload is a process that takes months and years to develop.
You need time for your muscles to adapt. In the push up example above, if you go from 3 sets of 10 push ups one day to 5 sets of 30 push ups the next day, you might not even complete that second workout and not get any adaptations at all.
An effective workout plan then addresses two main factors:
How to safely place as much mechanical tension on your muscles each week. All the main plans out there like the bro splits, the push pull leg and the full body routines are strategies to place load on your muscles. In the bro split you work one body part per day, usually over 5 or 6 days. In the push pull leg split you work on all your pushing muscles one day, your pulling muscles the second day and your leg muscles on the third day. The full body involves working each muscle group a little bit 3-5 times a week.
How to implement progressive overload in the long term to ensure continuous muscle adaptation. This is usually done via periodization, which is the planning of workout volume and intensity.
Periodization for muscle growth
Periodization is the planning of your workout progression. We saw that muscles adapt to given stimulus over time, and that we can't jump from doing 3 sets of 10 push ups one day and then 5 sets of 30 the next.
How you progress from the 3 sets of 10 to 5 sets of 30 is called periodization. I will write another article going into greater detail but here are the main points you should be familiar with.
A periodized plan should take you through phases that focus on accumulating the volume of your workouts and phases that increase the intensity of the workout.
Each phase typically lasts 4-6 weeks. By repeating volume and strength phases, you are making sure that your muscles get exposed to new weights.
Here's how this could work with bench press for example.
This is only an example of one exercise that would be part of a larger workout plan. We can still see a clear progression from week 1 to week 18. This person is starting week 13 with 10% more intensity than week 1. Note that it took 3 months to get there. The longer you can stick to a periodized plan, the more you increase your chances of making progress.
How long does it take to build muscle?
Timelines for muscle growth depends on your training age. People who start working out experience the fastest muscle growth in the first two years of training, then it slows down over time until the rate of muscle growth is 1-2 pounds of new muscle per year in advanced lifters.
You can see in the table above that a 10% increase may take up to 3 months. The more advanced you get, the smaller those increases between cycles will be.
Exercise selection matters
To get the best bang for your buck, you want to use exercises that allow you to put maximum tension on your muscles. These are usually multi joint exercises such as split squats, squats, bench press variations, pull ups, rows...
If we take a pec fly and a bench press, you can reasonably deduce that you can place more tension by doing the bench press because you can use much heavier weights for that movement.
The pec fly is better suited for the metabolic stress component of your workout.
We are all a bit different so it's ok if you use different exercises than me, or than anyone else for that matter. If you can drive more tension to a muscle by doing a different variation, then choose that one.
Key things to keep in mind when choosing your exercises:
- Is it safe?
- Does it use more than one joint?
- Can I use the optimal range of motion throughout the reps?
- Can I easily add weight or volume as part of a periodization plan?
How much should you do?
Volume is usually described as the number of sets multiplied by the number of reps. We established above that sets of 2-12 reps are ideal, so how many sets should you do?
Generally speaking, during a volume phase, anywhere from 12-25 sets per body part per week is good. To work this in a periodized model, you can start with 12 sets and add 2-3 sets each week.
During strength phases, 16-10 sets per body part per week is the general mark.
Nutrition for Muscle Growth
Eating enough protein will help your muscles recover faster and keep your training quality higher. Aim for a minimum of 0.8 grams of protein per pound of body weight. I'm 180 pounds so I aim for 180 x 0.8 = 144g of protein per day.
For a more in-depth article on protein requirements read this:
Try as much as you can to get your protein from whole, unprocessed foods. Protein shakes are a good solution to get more protein in your diet, but shouldn't be your main source of it.
I went through a phase where I'd take four scoops of protein powder every day. In hindsight that was too much. I was eating 200g of protein a day, which I could of used to for carbs instead.
Carbs are important for muscle growth because in order to help your muscles grow, you also need to be in a calorie surplus. This means you eat more calories than you use throughout the day.
You can get the extra calories from either carbs or fats. I personally like carbs better because they are cheaper and I enjoy eating them more than fats.
A good place to start is a 250 caloric daily surplus and then adjusting from there depending on how your progress goes. If your weight is staying the same, go to a 400 calorie daily surplus. If you notice you are getting too fluffly, reduce the surplus.
Important note: When building muscle, you will also gain a little bit of fat. This is something you will have to accept, regardless of what you may here from some ill-advised fitness pros out there.
Read more about caloric balance
And our last point here...
You need to sleep to grow muscles
A good night's sleep is necessary for your muscles to grow. Sleep is when most of the hormonal changes happen and when all the rebuilding of the muscles happens. Sleep also indirectly affects your muscle building plan by making you feel energized and bringing your best effort to your workouts.
The most important hormone secreted during sleep is the human growth hormone. As it's name implies, it helps us grow, and more specifically it helps our muscles grow and get bigger.
The longer you sleep, the more of this hormone your body produces. This alone is reason enough to take your sleep routine as seriously as your gym routine.
All the lifting and muscle breakdown in the world won't do you much if your body can't adapt to it, which is does during sleep.
Conclusion
Muscle growth is the result of placing increasingly challenging demands on your muscles which increase the size and amount of your sarcomeres. There are three different ways to achieve this: mechanical tension, muscle damage and metabolic stress.
Doing quality reps of multi jointed exercises during your workouts is a great place to start. Having a workout plan that works in progressive overload is the best way to make sure the stress you put on your muscles keeps growing over time, allowing for more adaptations.
Individual differences in anatomy, lifting experience and lifestyle all play a role in the designing of an effective plan. Use the principles outlined in this article to create the best plan for yourself and contact me if you need any help with it.
Happy gains,
Clem
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