I absolutely love the art of of bodybuilding. The science of gaining muscle has always fascinated me. I don't care too much about being on the beach, social media, or on stage showing off my physique. But I love the experimental process of creating a healthier body and mind. However, gaining muscle is still one of those topics that is terribly misunderstood.
For those who want to maximize their muscle gaining potential, stay away from lectures by gym bros. They will typically give you what they think worked for them or what they saw in some magazine.
You might hear, "You have to lift to failure." "If it's not heavy then you aren't working hard enough."
But if your goal is to gain muscle and you have been searching for the truth, I'm here to give it to you. Science says it makes sense to train across the continuum of repetition ranges. While there may be validity to focusing on the so-called "hypertrophy range" (6-12 reps), both high (15-20+) and low (1-5) repetition ranges should also be incorporated into your training program.
Not only does such an approach ensure full stimulation of the spectrum of muscle fibers, but it also serves as preparatory work for optimizing performance in the hypertrophy range. Low rep work enhances neuromuscular adaptations necessary for the development of maximal strength. When max strength increases due to low rep work then you can guarantee you will be stronger at moderate loads. This will give you greater mechanical tension which is key to gaining muscle. Let’s say your low rep work increased your bench press from 150 lbs to 225 lbs. Now you can go down and train in the moderate rep range (6-12) with loads that was close to your old max. That is an example of how you can increase mechanical tension.
Now let's look at the other side of that equation. Performance of higher-rep sets help over time raise lactate threshold. This means you will have the ability to delay the onset of fatigue. This will increase time under tension during moderate rep training. Time-under-tension refers to how long the muscle is under strain during a set of an exercise. If you normally train biceps with curls at 50 lbs and the set lasts around 10 seconds. What will happen if you trained biceps with 25 lbs and the set lasts for 30-45 seconds? Over time you will get stronger and can increase the time under tension at that 50 lb set.
There are infinite ways in which varied intensities can be integrated into program design. Perhaps the best way to ensure continued progress is by periodizing training rep ranges over time. This simply means that you should have times in your training where all rep ranges are covered. How you go about covering that spectrum comes down to personal preference and making your program fit you instead of vice versa.
Another option is to base loading strategies on the type of exercise performed. I've experimented with this a lot in the past. I would focus on low to moderate-reps (~1-10) for multi-joint movements such as squats, rows, and presses. And prioritizing higher rep training (15+) for single-joint, isolation type exercises like curls, shoulder raises, and leg curls.
There are no set in stone rules here. The response to training varies by the individual and that is why you shouldn't follow what Jimmy in the gym said is the best program. You need to experiment with different approaches and find out what works best for you.