WELCOME TO LIFTING SMART SERIES: We often get asked from our users and clients, various questions about workouts, body composition, nutrition, breaking plateau, setting new PRs and much more. In the past, we have been answering those questions and sending our clients articles from medical journals and related blogs but to our surprise, we always get the same response, “The article is too technical. I would love for someone to boil it down and provide me the summary”. So this lifting smart series will do exactly that.
In Lifting Smart Series, we will focus on sharing knowledge by means of answer question that arise when you are trying to build muscle, gain strength or live a healthy life style in general . This series will cover topics from muscle distribution, stimulation techniques, load vs intensity breakdown, exercise tips, myths, nutritional hacks and many more. However, instead of throwing all information at our lovely readers i.e. you, we will provide this information in more of a Q&A type.

So in today series, our topic is Muscle Fiber and why we as bodybuilder or strength trainer care.

Q 1: What are muscle fibers and why should a bodybuilder, powerlifter care about it?

A: Each muscle in our body has primary 2 type of muscle fiber i.e. Type I and Type II. Type II are further divided into Type II A and Type II X. But for simplicity lets just group them and call Type II fiber muscle. Type I are also called slow-twitch fiber and are used mostly during endurance exercises such as marathon running. On the other hand, type II fiber a.k.a fast-twitch fiber get exhausted pretty fast (max 30 minutes, depending on muscle group). With respect to muscle-building, we are majorly interested in type II muscle fiber increase. Read more [1]
The reason a bodybuilder, powerlifter and strength trainer should care is because we want to increase the size of those muscle fiber.

Q 2: Is Type I and Type II muscle fiber stimulated by same type of training?

A: Every muscle in our body has roughly 50-50 % split of Type I & II muscle fiber. So short answer is yes. However, there are certain muscle group like back muscle, where type I muscle fiber percentage is higher [4] than type II. But there has been no study that has provided concrete proof that certain type of workout can be used to target Type I vs Type II or vice-versa. [2]

Q 3: Is there anyway we can stimulate Type I and Type II separately?

A: YES. Even though we cannot isolate only Type I or Type II muscle fiber, we can still stimulate Type I or II based on varied load. Article [3], provides proof that
  • High intensity training activates more Type II muscle fiber when the load is between 50-70% of 1 Rep Max. Where as the Type I muscle fiber are activated more than the load is < 50% of 1 Rep Max.
  • Type II have higher peak percentage growth vs Type I.
Thus a varying load helps stimulate both type I and type II but the percentage is unknown.

Q 4: What is the good load and rep range for powerlifting, strength training and hypertrophy to maximize Type I and Type II muscle fiber stimulation during each workout?

A: Here are our recommendations. Please adjust them as per your experience level and training state.
For powerlifters/strength training: Mostly Heavy weight with low reps (3-5). Also include accessory exercises with reps ranging from (8-15) to stimulate both muscle fiber. An example would be to do 80% of exercise in workout with heavy weights (80% of 1RM) with low reps and 20% of exercises with medium-to-high reps with low load ( < 70% of 1 RM). If you are a powerlifter and want to track your workouts for free, you can download StrongLift 5×5 for free in GYMINUTES app. An excellent example of this Ivysaur’s 4-4-8 workout.
For Hypertrophy:  Mostly medium-high reps with 50-70% of 1RM weight followed by heavy load and low reps. So a sample workout would be 80% exercise of medium-to-high rep and 20% exercise on low rep high load.
** GYMINUTES have more than 10 hypertrophy workouts that you can download. A best example of a mixed workout is PHUL and PHAT. To checkout which workout is best for you, click here.
NOTE: In cases when you are performing medium-to-high reps sets with 50-70% of load, always aim for muscle failure for maximum stimulation.

Q 5: If failure is essential for hypertrophy after training, why even bother with multiple repetition ranges?

A: Just because Type II muscle fiber produces more hypertrophy than type I muscle fiber, it doesn’t mean type I doesn’t produce any hypertrophy at all. Performing multiple rep-range allows us to stimulate both Type II and Type I fiber of the working muscle. Read more [2]

If you have any follow-up questions, please email us at gyminutes @ or leave a comment below.