biodex Biostep 2 - Relationship of Calories Burned to Oxygen Consumption and METs; What are Watts?

Relationship of Calories Burned to Oxygen Consumption and METs
(See Figure 7.)
For every liter of oxygen consumed by the body during continuous exercise, the body
burns approximately 5 calories. Figure 7 below shows a 150 lb (68 kg) individual
exercising at a level requiring an oxygen consumption of 1 liter (1,000 ml) of oxygen each
minute. The individual must burn 5 calories each minute to supply the appropriate
amount of energy for the exercise. This translates to 14.6 milliliters of oxygen for each
kilogram of body weight per minute.
1,000 ml of oxygen / 68 kg of body weight = 14.6 ml/kg/min
To calculate the MET level, divide the oxygen consumption in ml/kg/min by 3.5.
14.6 ml/kg/min / 3.5 ml/kg/min= approximately 4 METs
4 METs
Figure 7. Calculating METs
NOTE: In a study designed to examine the test-retest reliability and concurrent criterion
validity of VO2 max on the BioStep 2 in community-dwelling older adults, results provided
preliminary evidence of reliable and valid estimates of oxygen consumption by the BioStep 2
when compared with the criterion standard of direct VO2 max measurement in the sample.
Reference: Mendelsohn, M.E., Connelly, D.M., Overend, J.J., Petrella, R.J. :Reliability and validity of
responses to submaximal all-extremity semi-recumbent exercise in older adults. Journal of Aging and
Physical Activity, 2007, 15, 184-194.
What are Watts?
Watts are a measure of power - the rate at which energy is produced. Watts measure the
amount of energy you burn per second when you exercise. One watt is defined as one
Joule per second, which is equivalent to about 4.2 calories per hour. If you exercise at 42
Watts for 100 seconds, you would burn 4200 joules or 1 calorie.
EXPLAINING METS, CALORIES, & WATTS — 18 —