Big Ten commissioner Kevin Warren expounded on what led to last week’s postponement of fall sports in an open letter released Wednesday, noting more specific concerns about member institutions’ ability to contain the spread of COVID-19.

Among those, Warren cited concerns from medical staffs that even a planned twice-a-week testing regimen for high-risk sports like football couldn’t adequately control the spread of the virus.

“As our teams were ramping up for more intense practices, many of our medical staffs did not think the interventions we had planned would be adequate to decrease the potential spread even with very regular testing,” Warren wrote.

Warren also cited concerns about the supply chain for testing, as well as the ability of institutions to adequately contact trace in the event of an outbreak. Because of that, there were worries of “significant disruptions to the practice and competition calendar.”

The NCAA has mandated that high-risk sports such as football test athletes twice per week, including within three days of competition. If an athlete tests positive, they are removed from competition for at least 10 days.

“We understand the disappointment and questions surrounding the timing of our decision to postpone fall sports, especially in light of releasing a football schedule only six days prior to that decision,” Warren wrote. “From the beginning, we consistently communicated our commitment to cautiously proceed one day at a time with the health, safety and wellness of our student-athletes at the center of our decision-making process.

“That is why we took simultaneous paths in releasing the football schedule, while also diligently monitoring the spread of the virus, testing, and medical concerns as student-athletes were transitioning to full-contact practice.”

Despite blowback from many Big Ten football players and their parents, which included calls for more transparency about the decision-making process, Warren noted the presidents and chancellors of the Big Ten voted “overwhelmingly in support of postponing fall sports” and the issue “will not be revisited.”

Last Tuesday, the Big Ten and Pac-12 became the first Power 5 conferences to shut down fall sports, while the Big 12, SEC, and ACC continue to move forward. At the time of the decision, Warren harped on the role uncertainty played in the Big Ten’s choice, but he failed to elaborate much beyond that.

In recent weeks, there have been questions about the role potential heart issues linked to COVID-19 — in particular, myocarditis, an inflammation of the heart muscle — may have played in the Big Ten’s decision. There has also been growing criticism of decision-makers relying on a recent myocarditis study in the Journal of American Medical Association, which found heart abnormalities in 78 percent of participants, because the data does not focus on younger people.

Last week, NCAA chief medical officer Brian Hainline said he knew of about a dozen cases of myocarditis in NCAA student-athletes.

“There is simply too much we do not know about the virus, recovery from infection, and longer-term effects,” Warren wrote. “While the data on cardiomyopathy is preliminary and incomplete, the uncertain risk was unacceptable at this time.”

Warren added that the availability of rapid testing equipment could mitigate concerns but that the supply of such tests is limited currently. He also emphasized that the financial implications of not having a fall season, especially football, were not part of the decision-making process “as the postponement will have enormous adverse financial implications.”

Warren said a “Return to Competition Task Force” is working on a plan for fall sports to resume “as soon as possible,” and potential winter or spring models will take into consideration how many football games can “reasonably be played” in a calendar year. Purdue coach Jeff Brohm recently released a proposal for an eight-game spring season followed by a 10-game slate in the fall of 2021.

“We understand the passion of the many student-athletes and their families who were disappointed by the decision,” Warren wrote, “but also know there are many who have a great deal of concern and anxiety regarding the pandemic.”