Use reasoning to lead to the answer of the following question:
This is an unavoidable physiological consequence of running. What is it?\nOptions:\n- breathlessness\n- increased heart rate\n- falling down\n- muscle bulk\n- calluses

increased heart rate
Increased heart rate is caused while running.

Increased heart rate is unavoidable.

It is physiological consequence of running.

.

So, the final answer is increased heart rate