What traits enhance an equine athlete's potential for speed and stamina? Writer Sushil Dulai Wenholtz provides some answers in an article that appears in the March edition of The Horse. Desirable traits include the following: Good Feet -- Big, strong feet with strong hoof walls and well-developed cups to the soles are preferred. Strong hooves provide structural stability that contributes to gait efficiency. They also minimize the development of hoof lameness that could interfere with performance. "A horse that is born with weak feet cannot be improved with feed supplements or diet," says Colorado veterinarian Nancy Loving, who competes in and judges endurance racing. Straight Limb Conformation -- "Horses with angular limb deformities suffer greater stress on one side of a joint than another, leading to degenerative arthritis," Loving explains. "Horses that paddle or wing because they toe in or out are likely to incur interference injuries as their muscles fatigue over the miles. Excessive excursion of any limb will hasten the onset of fatigue." All of this, of course, can inhibit athletic ability and shorten a horse's competitive career. Good Top Line -- A strong back and loins give the horse the ability to strongly engage his haunches. This provides the racehorse with a powerful "motor" in his hindquarters and helps an endurance horse drive down the trail or push up a mountain. Large chest -- A big chest "gives an opportunity for good lung excursion and provides housing for a big heart muscle," Loving says. Large lung and heart capacities generally mean greater aerobic capacity--thus maximum endurance and performance at maximum exertion. Large Cardiac Size -- A big heart is another plus for an equine athlete. (This should not to be confused with a desire to win, which horsemen refer to as "heart.") "I do believe a big physical heart can be bred for," says Ed Anthony, a pedigree consultant for Three Chimneys Farm near Midway, Ky. "And a lot of people even scan for that at the yearling sales, although I think it's an inexact science at that age. A horse's heart can grow so much between the time he's a yearling and the time he turns two or three." Good Shoulder Angle -- An open shoulder angle (between the scapula and the humerus) is important for a long stride. Short Cannon Bones -- Cannon bones should be relatively short for strength under stress, while the radius and the tibia should provide length to the legs.