Muscle Fiber Type and % Muscle Composition  

A simple test has been proposed to determine, or more correctly "estimate" your muscle fiber type without the use of expensive medical equipment, or without a muscle biopsy - an invasive technique. To begin with you just need to determine your 1 repetition maximum (1 RM) which is the maximum amount of weight you can lower and raise under control for only 1 repetition.

The exercises chosen for this test are usually compound movements involving many muscles and crossing more than one joint. These resistance exercises are called the bench press, the squat and the deadlift. Many other exercises can also be performed to estimate the fiber type of that particular group.

Safety Note:
1. Always have another person on standby when performing a 1RM, best is a personal trainer.
2. Do not perform this 1 RM test without an aerobic warm-up.
3. Do not perform this 1 RM test if you have not mastered the exercise and have less than 3 months resistance training experience.

Instructions for testing your 1 repetition maximum.

1. Start with one set of 15 Reps that you could do 20-25 with.
Drop 5 repetitions in each following set with a rest of about 1-2 minutes.
So that's sets of 15, 10, 5 and then finally 3 reps.
2. Rest about 3-4 minutes and then go for 2 reps.
3. Rest another 2-3 minutes and go for 1 maximum repetition.

While dropping repetitions in the following sets it should be quite clear that you need to simultaneously increase the weight. This will bring you to the maximum weight you can handle for one full rep, all by yourself. Of course your spotter or training partner must be there ready and attentive for assistance.

Calculate your Percentage Muscle Fiber Type

Armed with your 1 RM, use 80% of that weight for you next set. Perform and count the maximum number of repetitions you could perform with 80% of your 1 RM weight. How many did you do?

less than 7 repetitions = Fast twitch (FT) fibers
The muscle group is more likely to be 50% or more FT fibers.

greater than 12 repetitions = Slow twitch (ST) fibers
The muscle group is more likely to be 50% or more ST fibers.

Percentage Muscle Fiber Type Calculator (coming soon)

 

 
 
 
Reference:
Pipes, T.V. Strength training and fiber types. Scholastic Coach 63(8):67-71. 1994.
 

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DISCLAIMER: The information presented is for educational purposes only.
Always seek private professional advice prior to starting any health fitness program.