The first experiment was definitively easier than the later ones, and the last was the hardest.
It was harder to breathe [through the wider straw] than in real life because we normally don't get such a little and narrow space to breathe.
Breathing through the thinner straw was harder because you got an even narrower area than the wider straw. After a short bit of breathing through the wide straw, I felt like I was going to pass out.
As you become more active, your lungs probably speed up to keep up with the tempo of your body.