UNITS OF MEASURE
Textbook Appendix A
The measuring units most commonly used in exercise physiology are those variables related with
exercise, physiology, body size, and meteorology. Numerous variables are described with such measuring
units as kilogram (kg), liter (L), meter (m), and kelvin (K) in accordance with the International System (SI) of
nomenclature. Quite often in exercise physiology there will be a combination of units such as liters per
minute or milliliters per kilogram per minute.
SI is the universally accepted means of expressing measurement and is based on the decimal and
metric systems which simplifies the conversion between units.
Many units are derived from names of individuals who developed the measurement standard.
These names include joule, newton, kelvin, and watt. When using these terms spelled out we do not
capitalize them even though they are proper nouns. When expressing these names in combination with
other units we do not hyphenate the combined unit such as newton meter.
SI units are abbreviated only when they are associated with a number. Thus, the sentences below
are proper presentations of the term kilogram:
The subject weighed 79 kg prior to the start of the session.
Kilograms is a unit of measurement for mass.
While we do not capitalize the names of these great scientists who gave the measurements their
surnames, we do capitalize the abbreviation of newton (N), watt (W), kelvin (K). An abbreviation is never to
be written in plural. For instance, 123 kg is acceptable while 123 kgs is not. SI units do not require a period
to follow unless they are at the end of a sentence. Two component unit measurements such as newton
meters are abbreviated with a centered dot between the abbreviations (12 n·m) rather than with a dash. We
never mix abbreviations and unit names such as N·meter or numerals and names such as 250 newtons.
Thus, 12 n·m is correct but twelve n·m is not.
The proper presentation of the word ‘per’ SI is to use a centered dot preceding the unit with its
negative exponent following. The term liters per minute is expressed as L·min-1. One can use a slash such
as L/min. However it is not acceptable to use more than one slash in an expression so milliliters per
kilogram per minute is not to be abbreviated as ml/kg/min. Acceptable abbreviations are ml·kg-1·min-1 or
ml/kg·min.
Variables and Units of Measure
Mass – an SI base quantity represented by the SI base unit kilograms (kg). Mass is the quantity of matter in
an object. Under normal circumstances (gravitational pull of the earth) mass is equivalent to weight. One of
the most common measurements in exercise physiology is body mass. Body weight is a common term but
mass is more appropriate. Since body weight is used much more frequently in the United States we will
typically list weight as the measurement in labs. Most of the time we will require that you enter the
measurement in kg and lb. Pounds are a ‘customary’ unit and do not fit the SI system.
1 lb = 0.45 kg
1 kg = 2.2 lb
Sample calculation: ? kg = 151 lb * (0.45 kg/lb) = 68.5 kg
Length and Distance – also a base quantity; is typically described with the SI base unit the meter (m).
Longer lengths are described in kilometers (km), shorter lengths may be described in centimeters (cm) or
millimeters (mm). For very small units micrometers (µm) may be used. Height describes vertical length
expressed in m or cm.
Sample calculation: ? cm = 72 in * (2.54 cm/in) = 183 cm or 1.83 m
