(press a digit on the left side)

     6     No exertion at allNo muscle fatigue, breathlessness or difficulty in breathing.
     7     Extremely lightVery, very light.
     9     Very lightLike walking slowly for a short while. Very easy to talk.
    11     LightLike a light exercise at your own pace.
    12     Moderate
    13     Somewhat hardFairly strenuous and breathless. Not so easy to talk.
    15     HardHeavy and strenuous. An upper limit for fitness training, as when running or walking fast.
    17     Very hardVery strenuous. You are very tired and breathless. Very difficult to talk.
    19     Extremely hardThe most strenuous effort you have ever experienced.
    20     Maximal exertionMaximal heaviness.