Faster, Better, Stronger by Eric Heiden, MD, Max Testa, MD, and DeAnne Musolf
The Twitch Test
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Do you know your muscle composition? Are your muscles composed of primarily fast-twitch muscle fiber or slow-twitch muscle fiber? There are three ways to find out.

 

1. You can get a muscle biopsy for a precise measurement.

2. You can guess: Were you better at jumping high and sprinting or at running for a long time?

3. You can take the following vertical jump test.

 

The vertical jump test measures your ratio of fast-twitch to slow-twitch fibers by measuring the relative ratio of fast-twitch fibers in your leg muscles. In the lab we use a force plate for this, but you can do it at home as well.

 

The Vertical Jump Test

  • Mark a place on a wall as high as you can touch on your tiptoes, using wet or chalked fingers.
  • Again using wet or chalked fingers, jump as high as you can and touch the wall.
  • Do this three times.
  • Measure your best distance.

 

If you are fit and can jump 20 inches or more above the highest spot you could touch standing still, you have a higher ratio of fast-twitch fibers.

 

If you are fit and can jump eight to twelve inches, you do not have a high ratio of fast-twitch fibers. Of course, there is no way to say precisely the ratio without a muscle biopsy.

 

For more information on how to leverage your particular muscle composition in improving your fitness, see Chapter 4 in our book "Faster, Better, Stronger".