Because of an overactive thyroid, Houston's metabolism is stuck in fifth gear even when he downshifts to first. His hyperthyroidism was uncovered during a physical examination at the N.F.L. combine in Indianapolis in February.
When doctors at the combine sat Houston down and delivered the diagnosis, he was thrown for a loss. "What's a thyroid?" he asked.
Houston, 23, has since schooled himself on the body's regulatory center. And the Jets studied a scouting report on Houston from their medical staff before selecting him in the sixth round of the draft, with the 182nd pick over all.
It was a relief, Houston said, to find out there was a medical explanation for the mystifying symptoms he tried to shrug off during his senior season at Tennessee. Houston rushed for 1,005 yards in 2004, averaging 5.6 yards a carry despite never feeling quite right.
"I was tired a lot," Houston said. "I was sweating a lot. I was jittery all the time. My vision was blurry. It was awful. I didn't know what was wrong. I thought I was just getting old."
Trooper Taylor, who started coaching the running backs at Tennessee last year, could not understand why Houston would run two plays, then go to the sideline to catch his breath. Taylor had not been around the 6-foot, 225-pound Houston long enough to know whether he was dealing with a lackadaisical player or an overloaded one.
