Tuesday, 18 Jun 2024

%1-RM Test to Estimate Muscle Fiber Composition

The %1-RM test is a simple and indirect way to estimate the predominant muscle fiber type in a person’s muscle group. Athletes, especially those focused on strength or speed, are interested in knowing the composition of their muscle fibers. While an actual muscle fiber composition test is more accurate, it requires an invasive muscle biopsy and sophisticated analysis.

Purpose and Equipment

The purpose of the %1-RM test is to estimate the predominant muscle fiber type for any given muscle group. To perform this test, you will need free weights (barbells, dumbbells) or other gym equipment, as well as an assistant or spotter.

Test Procedure

Before starting the test, explain the procedures to the subject and screen for any potential health risks. Obtain informed consent and record basic information such as age, height, body weight, gender, and test conditions. It is essential to perform a standardized warm-up before proceeding.

To determine your one repetition maximum (1RM), lift the maximum weight you can lift with one repetition. Rest for 15 minutes, and then use 80% of your measured 1RM to perform as many repetitions as possible in a single attempt.

Scoring and Interpretation

The maximum number of times you correctly lift the weight is recorded. Use the values provided in the table below to determine the muscle fiber type based on the number of repetitions at 80% of 1RM.

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Variations and Considerations

There are two other protocols/assessments similar to the %1-RM test, although no specific references are available. One variation uses 80% of your 1RM (Dr. F. Hatfield Test) with a different interpretation, while the other uses 85% 1RM (Charles Poliquin Test). The results of these variations are interpreted differently.

It is important to note that performing a maximum weight lift is suitable only for advanced weight trainers. Proper technique and experience in the gym are essential before attempting this test. Also, the muscle fiber type results are specific to the muscle group tested and may not apply to other muscles in the body.

Advantages and Disadvantages

One advantage of this test is that the required equipment is readily available in most gymnasiums. However, it should be noted that the test is best used for test-retest measures and its results are specific to the equipment used and the technique allowed.


The %1-RM test is a valuable tool for athletes and fitness enthusiasts looking to estimate their muscle fiber composition. By understanding their predominant muscle fiber type, they can tailor their training programs to optimize performance. It is important to approach this test with caution and seek guidance from qualified professionals to ensure safety and accuracy.


Q: How accurate is the %1-RM test in estimating muscle fiber composition?

A: The %1-RM test is an indirect estimate of muscle fiber composition and may not be as accurate as actual muscle biopsy analysis. However, it provides a good indication of the predominant muscle fiber type and is widely used in the fitness industry.

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Q: Can the %1-RM test be performed without a spotter?

A: It is highly recommended to have an assistant or spotter present during the %1-RM test to ensure safety and proper form. Lifting heavy weights can be risky, and having someone to provide support and assistance is crucial.

Q: Are the results of the %1-RM test applicable to all muscle groups in the body?

A: No, the results of the %1-RM test are specific to the muscle group tested. Different muscle groups may have varying muscle fiber compositions, so it is important to consider this when interpreting the results.


The %1-RM test is an indirect method used to estimate the muscle fiber composition in a specific muscle group. Athletes and fitness enthusiasts can benefit from knowing their predominant muscle fiber type to optimize their training and performance. While not as accurate as invasive muscle biopsy analysis, the %1-RM test provides valuable insights. It is essential to approach this test with caution, seeking guidance from professionals, and ensuring safety during the lifting process.