How did exercise affect the time needed for the solution to change color? explain why the color change occurred (how does btb work?) ?

The exercise increases the rate at which the solution change to color yellow.

BTB [ Bromothymol blue] is an acid indicator that is used to measure the quantity of carbon dioxide that is produced after exercising for a specified period of time. The presence of carbon dioxide turns the blue solution to yellow. The higher the quantity of carbon dioxide present, the higher the rate at which the solution turns to yellow.