Eighteen McMinnville High School athletes experienced "compartment syndrome," which caused soreness and swelling in their triceps and high levels of creatine kinase, a protein that can harm the kidneys. Three players had surgery to relieve swelling.
Authorities said the cause was not yet known, but the condition can be the result of exercise or the use of certain medications. All but one of the players who became ill worked out last Sunday at the high school's wrestling room, where one player says the temperature reached 120 degrees.
Two players were released by Saturday night from Willamette Valley Medical Center, a spokeswoman said.
Superintendent Maryalice Russell told The Oregonian newspaper she doesn't believe the workout from first-year coach Jeff Kearin was excessive. She said she has no evidence that steroids or other supplements were involved.
"I don't have any information at this time that would indicate that's the case," she said. "I'm continuing to look at additional information as it may come my way."
Oregon School Activities Association executive director Tom Welter said the organization's medical committee will investigate and make recommendations to the executive board after its next meeting in September. The OSAA oversees school sports in the state.
Practices for all fall sports start on Monday.