Morning Olympic finals are not going to be a problem insist Australian swimming stars Emma McKeon and Cate Campbell despite some early evidence at the national championships.

McKeon pipped Campbell to the 100m freestyle title at the nationals on the Gold Coast on Friday morning, clocking the world's third-fastest time this year with a 52.49.

That winning time was however slower than Campbell's 52.43 in Thursday night's heats - the quickest 100m freestyle time by a woman in 2021 and fast enough to have won gold at Rio in 2016.

McKeon's win came against a hot field that also including third-placed Madison Wilson and Cate's sister Bronte, who came fourth with a 53.80.

The fact most of the field went slower than their heat times was of no concern to McKeon who doesn't feel there's a need to unlock a secret to competing in morning finals.

The finals at the nationals are being held in the morning to reflect the schedule swimmers will face at the Tokyo Games.

"It is physically a little bit harder I think getting up in the morning, but actually I don't really find it that hard because we train early in the morning and this is four hours after I usually train," McKeon said.

"It's more of a mental state as well. Just knowing it's a final.

"Once we get to an Olympics, it's an Olympic finals so no matter what time of day it's on, you're going to be ready to go.

"In Rio we were swimming at midnight or something, we'll be ready no matter what."

Campbell experienced morning finals at the 2008 Beijing Games and said while she suffered somewhat from her fast swim the night before, she was happy with her form heading towards June's Olympic trials.

"Coming into this competition I had four 100s until Olympic trials and so it wasn't so much about progressing from heats to finals, it was just about getting some good, solid racing in," Campbell said.

"Pushing my training and seeing where I was at. So really happy with the swim last night.

"Pretty happy with this one this morning. It'll really set me up for a good few weeks of training."

In Friday's other headline event, Olympic champion Kyle Chalmers completed the 100m-200m freestyle double with a comfortable win in his pet event.

The 22-year-old said he may look at racing in the butterfly at the Olympic trials but was also still carefully managing his shoulder after surgery last year.

"I'm noticing it a lot but I'm doing everything in my power almost every hour of the day to stay on top of it," Chalmers said.

"I won't take having healthy shoulders for granted ever again."

In other results on Friday, veteran Emily Seebohm finished second in the 100m backstroke behind Kaylee McKeown as the 28-year-old chases a fourth Olympic appearance.

The championships continue on Saturday and Sunday at the Gold Coast Aquatic Centre.