Question

Why is the motion of athelete moving along the circular path with constant speed considered to be an accelerated motion?

Answer 1

You may be running along the circular path with the same speed, but the direction constantly changes because it is a circular path meaning the direction is tangential and changes at every point on the circle. Since the direction changes, velocity changes (because it is a vector quantity). And we know that if a change in velocity occurs, it means acceleration is there.
Additional info- This acceleration is perpendicular to the tangential direction of motion (and thus this towards the centre).