%1-RM Test to Estimate Muscle Fiber Composition

This is a simple indirect test that is used to estimate the predominant muscle fiber type - slow twitch or fast twitch. It is interesting for athletes to know the composition of their muscle fibers. If they are primarily a strength or speed athlete, they want fast twitch fibers. For endurance athletes, more slow twitch fibers is optimal. This test does not replace an actual muscle fiber composition test, which would be more accurate but involves an invasive muscle biopsy and more sophisticated analysis.

number of reps at 80% muscle fiber type
< 7 > 50% fast twitch (FT)
7 to 12 equal proportion of fiber type
> 12 > 50% slow twitch (ST)

number of reps at 80% muscle fiber type
< 7 mostly fast twitch (FT) dominant
7 or 8 mixed fiber type
> 8 slow twitch (ST) dominant

number of reps at 85% muscle fiber type
< 5 mostly fast twitch (FT) dominant
5 mixed fiber type
> 5 slow twitch (ST) dominant

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