You are responsible for developing an exercise prescription for a post-CABG (cor

ID: 50248 • Letter: Y

Question

You are responsible for developing an exercise prescription for a

post-CABG (coronary artery bypass graft) surgery patient who has

just been referred to Phase II cardiac rehabilitation. Based on the

results of his pre-discharge GXT (stress test), the intensity of

exercise prescribed should be 4 METs. He weighs 207 lbs.

Compute the following:

a. Walking speed on a horizontal treadmill (0% grade)

b. Treadmill grade for a speed of 3.0 mph

c. Resistance setting in kp on a Monark bicycle ergometer

(pedaling at 50 rev min-1)

d. Stepping rate for a 9 inch step bench

The following conversion factors are to be considered:

1 MET = 3.5ml/g/min of volume of oxygen consumed (VO2)

1 mile per hour = 27 meters per minute

a. Walking speed on a horizontal treadmill is calculated as follows:

VO2 = (0.1 × speed) + (1.8 × speed × grade) + 3.5

For a MET value of 4, VO2 is 4 × 3.5 = 14. Let us use x for speed. Therefore,

14 = 0.1x + (1.8 × x × 0) + 3.5

14 = 0.1x + 0 + 3.5

0.1x = 14 – 3.5

0.1x = 10.5

X = 105 meters/min

b. More information required

c. Resistance setting in KP on a Monark bicycle ergometer for pedaling at 50 rev/min is: (207 pounds = 94 kg)

R = weight × D × pedaling cadence in rpm

For a Monark bicycle, the value of D = 2.4

R = 94 × 2.4 × 50

R = 11280 kilograms = 110 kp

d. Stepping rate for a 9 inch step bench is:

VO2 = 0.2 (step rate) + 1.33 × 1.8 × step height × step rate + 3.5

(the value 1.33 is O2 cost of stepping down and 1.8 is O2 cost of vertical ascent)

14 = 0.2x + 1.33 × 1.8 × 2.286 meters × x + 3.5

14 = 0.2x + 5.47x + 3.5

10.5 = 5.67x

X = 1.85 / min

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