1 Very light:
You feel hardly any exertion.
Feels like you can maintain for hours. Easy to breathe and carry a conversation.
Feels like you could go on like this for a long time and have a conversation.
4 Somewhat heavy:
Breathing is difficult, short conversations are possible.
All in all still well feasible, but exhausting.
6 Breathing heavily, can hold short conversation:
Still somewhat comfortable, but becoming noticeably more challenging.
7 Very heavy:
Holding conversations feels uncomfortable.
8 Borderline uncomfortable:
It is still possible to speak single sentences, but coherent conversations are no longer possible.
9 Very very heavy:
Can barely breathe and speak only a few sentences.
10 Like in competition:
Feels almost impossible to keep going. Completely out of breath, unable to talk. Cannot maintain for more than a very short time.