Fiitjee q doubt.

okie...
in general pH will have tendency to lower down
becoz
During exercise, the muscles use up oxygen as they convert chemical energy in glucose to mechanical energy. This O2 comes from hemoglobin in the blood. CO2 and H+ are produced during the breakdown of glucose, and are removed from the muscle via the blood. The production and removal of CO2 and H+, together with the use and transport of O2, cause chemical changes in the blood. These chemical changes, unless offset by other physiological functions, cause the pH of the blood to drop.

but due to presence of buffers in blood pH change is resisted to large extent[1]

acc to my sir--

CO₂ → HCO₃^- ..
this rxn takes place in blood..

CO₂ increases..therefore H+ increases..therefore pH increases..

en.wikipedia.org/wiki/Metabolic_acidosis

www.lifesteps.com/gm/Atoz/ency/respiratory_alkalosis.jsp