sorry for taking so long to reply to this I wanted to find a good post explaining why, this is what I found, this isnt in my words I copy/pasted this

Cardio goes to the gutter because Tren promotes inflammation via bronchial dilation that restricts the passage of airway in certain areas that relate to the functionality of your prostaglandin. This is why it's sometimes hard to breathe during the day, even while doing normal activities while on Tren , or where the "tren cough" probably came from. Bronchodilator/prostaglandin formation are 2 key words to search if you want to really delve into the correlation between Tren and aerobic capacity. A good protocol for the advanced users might be to add clen while on tren. Since clen is a bronchodilator it will improve breathing while doing cardio.