2.1.4. Exercise Test Modalities

Depending on the method of exercise, exercise tests are usually performed on a treadmill or cycle ergometer [4]. Treadmills reflect a more physiological form of exercise but require more space and are more expensive than cycle ergometers. For test adequacy, it is important to use the treadmill handrails for balance only and to avoid gripping the handrails while exercising, in order to prevent peak oxygen uptake values being overestimated. Electrically braked cycles are calibrated in watts (W) and allow for a better ECG signal compared with treadmills; however, their biggest limitation is the termination of the test due to the fatigue of the quadriceps muscles. This affects test duration, and the maximal oxygen uptake attained is lower by 10–15% compared with that obtained on a treadmill [3]. From a technical point of view, bicycle tests should be executed in a proper way—i.e., with adequate seat adjustment and a knee flexion around 25 degrees of full extension.

2.1.5. Predicted Functional Capacity

Exercise capacity is reported in metabolic equivalents of tasks (METS). The MET unit reflects the resting volume oxygen consumption per minute (VO2) for a 70 kg, 40-year-old man, with one MET equivalent to 3.5 mL/min/kg of body weight [5]. The appropriate assessment of predicted functional capacity determines the appropriate test protocol.

Functional capacity depends on [6]:


There are many formulas for predicted MET calculation [7,8]:

1. Morris formula for men:

Predicted MET = 18.0 − 0.15 × age (years)

2. Gulati formula for women: Predicted MET = 14.7 − 0.13 × age (years)

Predicted functional capacities for men and women in relation to age according to the Morris and Gulati formulas:

Twenty years old: women 12.1 MET, men 15.0 MET. Thirty years old: women 10.8 MET, men 13.5 MET. Forty years old: women 9.5 MET, men 12.0 MET. Fifty years old: women 8.2 MET, men 10.5 MET. Sixty years old: women 6.9 MET, men 9.0 MET. Seventy years old: women 5.6 MET, men 7.5 MET.

The Duke Activity Status Index and the Veterans Specific Activity Questionnaire have been developed to assess the intensities of activities of daily living [9,10].

Duke Activity Status Index (DASI) comprises 12 questions assessing daily activities, with each item equaling a specific metabolic cost in MET. Patients are asked to identify each activity they can perform (Table 4).

Oxygen uptake = (0.43 × sum of points from positive answers) + 9.6.


### **Table 4.** Duke Activity Status Index.

Source: Adapted from [9].

Similarly, the Veterans Specific Activity Questionnaire (VSAQ) consists of 13 items estimating aerobic fitness in cardiac patients and measures the maximal level of physical activity that patients can achieve (Table 5). Predicted MET = 4.7 + 0.97 × the highest tolerable MET from questionnaire − 0.06 × age.
