UNITED MEDICAL CORP <UM> SELLS UNIT United Medical Corp said it will sell its Trotter Treadmills Inc unit. The company said the sale is in line with its strategy of refocusing on its health care service business. It said it had received interest from several parties, but no agreement has yet been reached. Trotter Treadmills makes motorized treadmills for the exercise enthusiast and fitness club market. It said its sales for this year are projected to be over 10 mln dlrs.