Metabolic Training Equations DEMO – Cardiac Rehab Scenario

Scenario..

You are the exercise specialist in a cardiac rehabilitation center. A patient (age 63 years, height 5″11″, BW 85 kg) will come to your facility to begin a training program. His chart indicates that his doctor wants him to lose 10 lbs of body weight, in order to better control the first signs of Type II diabetes. He must lose the weight in 6 months, when his next check-up will take place. Your job is to design a training program for your patient, so that he will achieve that goal.

ASSUMPTIONS

In order to simplify the math for this example, we will assume that the patient’s weight is 85 kg throughout the training period
The weight should be lost from the body’s fat mass. Therefore, your patient must lose 10 lbs, or else, burn 35,000 kcal worth of energy.
The improvements in physical conditioning (e.g. increased RMR were not significant)
Your patient indicates that he would much prefer to exercise on the cycle ergometer, because his knees are bothering him a little when he walks.
Your patient said he can practice 4 days/week
Aside from the exercise session, nothing else (e.g. lifestyle, diet) has changed in his daily routine.

CALCULATIONS

He will be in your facility for 6 months = 26 weeks. Since he will exercise 4 times per week, he will participate in 104 workout sessions. Therefore, he must burn 35,000 ÷ 104 = 336.5 kcal each time he shows up.

Since 5 kcal of energy require 1 liter O2 to be consumed, the patient’s total oxygen consumption for each workout must be 336.5 ÷ 5 = 67.3 L O2/day, or 67,300 ml/day.

Let us assume your patient can only work out for 60 minutes, so for each minute he must consume 67,300 ml ÷ 60 min = 1,121 ml O2/min (absolute VO2).

The next step is to find what pedaling frequency and resistance setting you should use, in order for our patient to achieve this oxygen consumption.

An average pedalling frequency that he feels comfortable with is 50 rpm, in which case the distance travelled by the wheel is 300 m (see your lab manual for more explanations).

The last piece of information needed is how much weight should we place on the tray?

In order to find the answer, we will use the cycle ergometer metabolic equation:

VO2 = (power × 2) + (3.5 × BW)

By substitution, we have 1,121 = (power × 2) + (3.5 × 85)
By solving for power (the unknown factor) we find that power = 411.75 kgm/min.
So, in 1 min he performed mechanical work equal to 411.75 kgm. Since kgm is the unit of Work, and Work = Force × Distance, and the distance traveled is 300 m, we can find that the load applied is 1.37 kg.

SUMMARY

Your patient needs to exercise 4 times per week for 6 months, on a cycle ergometer, at a pedaling frequency of 50 rpm, against a resistance of 1.37 kg, in order to lose 10 lbs in 6 months.

Obviously, some of the assumptions we made at the beginning will be violated, so you will need to adjust the workload accordingly.