What Causes Prominent Veins On On Lower Leg?

I have started a new boot camp exercise group. I excercised this morning and after I got out of the bath, I noticed veins in the front part of my leg very prominent. From my knee down. I am 55 yrs. old and have been excercising since mid march. No pain but was just wondering if this is something I should get checked out. About 5 yrs. ago I would walk on the treadmill and when I would walk for about 5-10 minutes I would have to stop because my legs would get so tight it would hurt. Rest 2-3 minutes and resume my walk for the rest of the 45 minute time.