On the team's Web site, Henderson succumbed to heat exhaustion in the final few minutes of a practice session Tuesday morning. He was carted off the field and whisked away in an ambulance.
"'Big John' had an episode where he was short of breath, so we went into the mode of getting him cooled down and treated," said Coach Jack Del Rio, who indicated that the team now will have a scaled-down practice regimen. "We anticipate he'll be just fine."
Del Rio does not think weight was a problem. Henderson is 6-7, 328 pounds.
"He's not terrible out of line from where we want him to be," Del Rio said.
Henderson follows Larry Smith, who had a similar episode on Sunday and was kept for overnight observation, also at Jacksonville's Baptist Hospital.
Smith did not practice with the team Tuesday morning. Del Rio said he had a separate indoor workout.