ORLANDO, Fla.-- The words "I can't" are generally not in an airman's vocabulary, but airmen need to let their chain of command know if they are overworked, Chief Master Sergeant of the Air Force James Cody says.

"It is essential — and I tell you, supervisors should be paying attention enough that they know it themselves," Cody said Thursday at the Air Force Association's 2015 Air Warfare Symposium here. "There's no doubt that they should be paying attention to how hard their airmen are working and if what they are asking them to do reasonable and sustainable. If they're not, we need to have a conversation with them, too."

The Air Force is the smallest in its history as an independent service, yet the requirements being asked of airmen have not diminished.

However, airmen still need time to rest and reconnect with their families, Cody told Air Force Times.

"It can't be: I go to work for 14 hours a day and I go home and pass out to get up to work for 14 hours a day tomorrow," he said.

Cody stressed that airmen not in a combat environment need to let their leadership know when their workload is unsustainable instead of trying to work at a burnout pace because they feel the mission would fail otherwise.

"That needs to be elevated to the right level of leadership within that organization," he said. "I promise you: At some given point in that chain of command, someone is going to say, 'Knock it off; that's not healthy; that's not sustainable and we're not going to do it.'"

Cody said that he and Chief of Staff Gen. Mark Welsh have both let airmen know that they have the "top cover" to let their chain of command know if their work schedule is unreasonable.

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"Both Gen. Welsh and I have said this over and over and over again: 'Tell us what it is that you're going to stop doing,'" Cody said.

One symptom of the Air Force being overworked may be that 16 percent of airmen reported on the most recent Periodic Health Assessment that they do not get the minimum amount of exercise per week that is recommended by the U.S. government.

Two airmen told Air Force Times that they do not have enough time during the day to work out because they routinely work more than 12 hours.

But Cody said he does not feel the Air Force needs to have mandatory physical training because commands are already supposed to provide airmen with time enough to exercise three times a week.

If airmen are not getting that much time to work out, they should talk to their chain of command, Cody said.

"The direction of the Air force is they should be provided an opportunity to PT for 90 minutes, three times a week," he said. "So, 'should,' is not a suggestion. It means: Unless impossible, that should be taking place."