Sickle cell trait: The silent killer
Dale Lloyd II had already lifted weights with his teammates when he took the field in the Texas heat for what would be the final workout of his life.

It was Sept. 24, 2006, the day after the Rice football team suffered a humiliating 55-7 loss to Florida State. Rice coach Todd Graham cancelled practice for most of the team, but Lloyd and other underclassmen who didn't play much against FSU were told to report for Sunday conditioning.

After hitting the weights, the group lined up outside to run. Court records provide a disturbing account of what came next.

Lloyd and his teammates ran 16 consecutive 100 yard sprints – almost a full mile. Early on, Lloyd started showing signs of distress, breathing heavily and suffering muscle tightness in his legs. As the workout progressed he had trouble standing. Later, he even had trouble just holding up his head.

Lloyd was always known as a hard worker both in the classroom and on the field, but as the sprints continued some of his teammates became concerned about his condition. He was normally one of the team's fastest players, but that day he lagged 30 to 40 yards behind teammates, including the bulky offensive linemen. He ran with his head down, clutching his sides in pain.

Some witnesses said when Lloyd's teammates tried to help him, an assistant strength and conditioning coach ordered them to leave Lloyd alone. He finished 16 full sprints before collapsing. He never regained consciousness.

A medical examiner later determined Lloyd died on Sept. 25, 2006, from complications of sickle cell trait.

Since 2000, nine college football players have died from sickle cell trait complications, by far the biggest non-traumatic killer in the sport. The list includes UCF wide receiver Ereck Plancher after an offseason workout in March 2008. Last month, a jury found the UCF Athletics Association negligent in Plancher's death and awarded his parents $10 million.

At least 17 high school and college athletes' deaths have been tied to sickle cell trait during the past 11 years. The group includes Olivier Louis, a player at Wekiva High School near Orlando, who died on Sept. 7, 2010, following his first football practice.

Ereck Plancher's father, Enock, said he does not understand why these deaths have not caused more outrage or prompted more changes to protect athletes.

"Football is sport," he said. "It's not supposed to kill you. It has to change."

What is sickle cell trait?

Every hospital in the United States is required to test newborns for sickle cell trait. The state of Florida began testing in 1988.

Testing was started to help determine which children have sickle cell anemia, a debilitating blood disease that warps red blood cells and can cause strokes, fever and ulcers. The disease typically reduces a person's life span.

People with sickle cell anemia have Hemoglobin S, a variant of two genes that cause flexible doughnut-shaped red blood cells to collapse into rigid crescents or sickles. The cells get sticky, block blood flow and can cause major organ damage.

People with sickle cell trait do not have sickle cell anemia.

Sickle cell trait carriers have Hemoglobin SA, with one gene capable of making warped red blood cells and one that produces normal red blood cells. Most people with the trait typically don't suffer any symptoms or health problems related to the condition.

However, a growing number of medical experts argue sickle cell trait can be a silent killer.

When a person with sickle cell trait is under extreme physical stress — such as during Lloyd's workout at Rice and Plancher's workout at UCF — their blood cells can warp into the flat, rigid sickle cell shape. The sticky red blood cells attack muscle tissue, blocking oxygen flow and quickly shutting down vital organs.