It should never be difficult to breathe when doing cardiovascular activities. You should be breathing deeper and more rapidly. If that is the reason, it's because your heart requires more oxygen to unlock the potential energy in your body. If by difficult you mean it hurts, you should consult a medical professional.
because sharks have to swim to breath so if they dont swim then they dont breath causeing them to sink and die. because sharks have to swim to breath so if they dont swim then they dont breath causeing them to sink and die.
There Is None. You DONT need any physical activity to be a pediatriction. it is told to say you need about 60 minutes a day,just to stay healthy.(: Hope i helped.
because sharks have to swim to breath so if they dont swim then they dont breath causeing them to sink and die. because sharks have to swim to breath so if they dont swim then they dont breath causeing them to sink and die.
you get fat and sit on the couch and dont get out and get a girlfriend or boyfriend lazy bums
they dont
they dont
Of course dogs breathe when they run! they dont hold their breath!
we dont
if you dont breath then you die
your muscle dont respire, your heart and lungs need to respire more whilst taking part in a physical activity.
we breath out carbon dixocide but we dont use carbon to breath trees do
Because you dont breath when you drink water