Oxygen consumption and caloric expenditure
Exercise testing is done on treadmills,
cycles, and arm ergometers. For all these testing modalities, there are
metabolic equations that determine oxygen consumption and caloric expenditure.
The equation for walking on a motor driven treadmill is .1 (m/min.) +( 1.8 x
m/min. x % grade) + 3.5 with the result being in the units of ml/kg/min. The
equation for running on a motor driven treadmill is .2(m/min.) +( .9 x m/min. x
% grade) + 3.5. There is a horizontal, vertical, and resting component. The
first part of the equation is the horizontal or speed. The grade is the
vertical component with the first number representing the foot drag, the second
is meters per minute, and last is percent grade. The foot drag decreases when
someone runs because of the short flight component. Meters per minute is the
product of 26.8 and mile per hour. A two-hundred-pound man walks at 3.6 mph at
a ten percent grade for twenty-five minutes. Use the walking equation and multiply 26.8 by 3.6
mph for the conversion to meters per minute. In this example, it equals 96.48
m/min. The product of the meters per minute and .1 is 9.648 which is the
horizontal component. The vertical component calculation is (1.8 x 96.48 x .10)
which equals 17.37 ml/kg/min. The resting component is 3.5 ml/kg/min. When added,
the total is 30.52 milliliters of oxygen per kilogram of bodyweight per unit of
time or one minute. This is the measure of the amount of oxygen a person takes
in and utilizes for the activity. In this case the man weighs two hundred pounds
or 90.9 kilograms and exercised for twenty-five minutes to arrive at 69,357
milliliters of oxygen being utilized during this exercise bout. Divide this by
one thousand to get 69.36 liters. The liters of oxygen us multiplied by five.
The product is 346.78 calories burned.
Cycle and arm ergometers can also
be used. To determine the workload on either is the product of revolutions per
minute, flywheel travel, and kilograms of resistance. This calculation yields kilogram meters which
is a unit of force. The metabolic equation for a cycle is 2(kgm) + 3.5 (bodyweight
in kilograms). The equation for arm ergometry is 3 (kgm)+ 3.5 (kg). A two
hundred pound or 90.9-kilogram man pedals at 60 rpm on a cycle with a ^ meter
flywheel travel at a resistance of two and a half kilograms. Flywheel travel means
if you turn the pedals one complete revolution, it takes you a certain
distance. The workload is calculated at 900 kgm. This is doubled to yield 1800
which is added to the product of 3.5 and 90.9 kg. The total is 2118 ml/min.
This person pedals for twenty minutes and takes in and utilizes 36,318
milliliters of oxygen for the exercise. Again, this is converted to 36.32
liters and multiplied by five for a total of 182 calories burned.
The resting component as I mentioned earlier is the value
3.5. At rest, people consume and utilize 3.5 ml/kg/min. or one MET. MET stand
for metabolic equivalent to oxygen consumption. METs can be used to gauge
exercise intensity for clients or patients as related to activities. A cardiac
rehab patient ask “Do you think it is safe for me to go deer hunting this
weekend?” His Met levels are higher than the values to go hunting if he doesn’t
drag the carcass. You tell him this and he is very happy that he can go hunting
with his son and can be almost certain he will have no difficulties. There is a
MET table for activities from a to z in ACSM Guidelines for Exercise Testing
and Prescription that may be used to determine appropriate exercise intensity
levels for patients and clients. Please visit tpnbodyperfect.com and check out
our blog at https://tpnbodyperfect.blogspot.com/
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