In the jump reach test, the subject jumps straight up and the distance measured, typically by the difference in height of the outstretched arm and hand before and during the jump. The test is used as a measure of leg power. The Lewis nomogram was developed to convert the distance jumped to power output.


power output in kg•m/s =

= SQRT (4.9) * (weight in kilograms) * SQRT (distance jumped in meters)


power output in ft•lb/s =

= 4 * (weight in kilograms) * SQRT (distance jumped in feet)



• SQRT indicates the square root function


1 watt =

= 9.80665 kg•m/s

= 1.35582 ft•lb/s


factor to convert kg•m/s to ft•lb/s: multiply by 7.233

factor to convert kg•m/s to horsepower: multiply by 0.0131

factor to convert ft•lb/s to horsepower: multiply by 0.0018


Note to Fox (1984):

• The conversion factor between kg•m/s and ft•lb/s given as 7.32, but the value given above can be derived from the units themselves or is given in tables (Weast, 1979).

• The units for distance jumped are not given, but meters and feet appear to agree with the nomogram.

• The metric equation seems to agree better with the nomogram.


Limitations (Harman et al, page 117):

• The formula does not use standard units.

• Gravity is not accounted for.

• It is unclear if the test measures peak or average power.


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