arena Swim of the Week: Mollie O’Callaghan Rips Fastest 100 Free Back-Half Ever

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Disclaimer: Swim of the Week is not meant to be a conclusive selection of the best overall swim of the week, but rather one Featured Swim to be explored in deeper detail. The Swim of the Week is an opportunity to take a closer look at the context of one of the many fast swims this week, perhaps a swim that slipped through the cracks as others grabbed the headlines, or a race we didn’t get to examine as closely in the flood of weekly meets.

If you’ve been following the first few days of action at the 2022 Australian Swimming Championships in Oaklands Park, you’re well aware the competition has been a standout one for up-and-coming phenom Mollie O’Callaghan.

The 18-year-old rising star has qualified to swim three individual events at the World Championships in as many days at the meet, which serves as a qualifier for next month’s Worlds in Budapest, but thus far the performance that stands out above the rest came in the women’s 100 freestyle.

Australia had the gold and bronze medalists in the event at last summer’s Olympic Games, but both Emma McKeon and Cate Campbell aren’t competing at this year’s trials, nor is veteran Bronte Campbell. Those absences meant that three out of the four members of the Australia’s gold medal-winning and world record-setting 400 free relay from the Tokyo Games wouldn’t be in the field in Oaklands Park, leaving an opening for the next generation to fill the void.

O’Callaghan did just that and then some, as she started out by becoming the first woman sub-53 in the 100 free this year in the prelims, clocking 52.83 for a new best time.  She had previously been 53.08, done leading off Australia’s 400 free relay in the prelims at the Olympics last summer.

What stood out about that 52.83, beyond the impressive overall time, was O’Callaghan’s closing 50, as she came back in a scorching 26.73 (nearly even-splitting after opening in 26.10).

That briefly stood as the fastest textile back-half of all-time in the women’s 100 free, overtaking Bronte Campbell‘s 26.80 from the 2018 Commonwealth Games. It also ranked third overall, trailing two from Germany’s Britta Steffen at the 2009 World Championships.

In the final, O’Callaghan was faster on both 50s, getting out in 25.92 before coming home in a scorching 26.57, culminating in the victory and a final time of 52.49.

That swim further improved O’Callaghan’s world-leading time, and made her the eighth-fastest performer in history. Runner-up Shayna Jack (52.60) also moved to #2 in the world for the season, and Australia now occupies four of the top-five times globally this season.

2021-2022 LCM Women 100 Free

View Top 28»

But about that back half.

O’Callaghan’s 26.57 closing split ranks as the fastest in history, overtaking Steffen’s 26.61, which was done when she set the world record at 52.07 in Rome.

All-Time Closing 50s, Women’s 100 Freestyle (LCM)

Data courtesy of Daniel Takata. Follow his Swimming Stats page on Instagram here

Athlete Back-half split Final time Event
Mollie O’Callaghan 26.57 52.49 2022 AUS Nationals
Britta Steffen 26.61 52.07 2009 World Championships
Britta Steffen 26.62 52.22 2009 World Championships
Mollie O’Callaghan 26.73 52.83 2022 AUS Nationals
Amanda Weir 26.76 53.02 2009 World Championships
Bronte Campbell 26.80 52.27 2018 Commonwealth Games
Ranomi Kromowidjojo 26.83 52.75 2012 Eindhoven Swim Cup
Sarah Sjostrom 26.84 52.78 2015 World Championships
Sarah Sjostrom 26.86 52.73 2014 Stockholm Open
Sarah Sjostrom 26.88 51.71 2017 World Championships
Emma McKeon 26.88 51.96 2021 Olympics
Sarah Sjostrom 26.92 53.05 2011 NED Open
Simone Manuel 26.92 52.54 2018 USA Nationals
Sarah Sjostrom 26.93 52.93 2014 Stockholm Swim Cup
Penny Oleksiak 26.93 52.72 2016 Olympics

Here’s a look at the top 10 performers in history and how they split their race:

Rank Swimmer Final Time Opening 50 Closing 50 Meet
1 Sarah Sjostrom (SWE) 51.71 24.83 26.88
2017 World Championships
2 Emma McKeon (AUS) 51.96 25.08 26.88
2021 Olympic Games
3 Cate Campbell (AUS) 52.03 25.09 26.94
2018 Pan Pacific Championships
4 Simone Manuel (USA) 52.04 24.81 27.23
2019 World Championships
5 Britta Steffen (GER) 52.07 25.46 26.61
2009 World Championships
T-6 Bronte Campbell (AUS) 52.27 25.47 26.80
2018 Commonwealth Games
T-6 Siobhan Haughey (HKG) 52.27 25.1 27.17
2021 Olympic Games
8 Mollie O’Callaghan (AUS) 52.49 25.92 26.57
2022 Australian Championships
T-9 Mallory Comerford (USA) 52.59 25.51 27.08
2017 World Championships
T-9 Penny Oleksiak (CAN) 52.59 25.42 27.17
2021 Olympic Games

O’Callaghan’s closing ability was on full display once again on Friday in the final of the women’s 200 free, as she came home faster than winner Ariarne Titmus to place second in a personal best time of 1:54.94.

Titmus swam the third-fastest time in history in 1:53.31, closing in 28.79, while O’Callaghan’s final 50 split was 28.54. This resulted in O’Callaghan placing second by over nine-tenths of a second after turning sixth at the 100m wall and fourth at the final turn.

Less than an hour later, O’Callaghan was back in the water taking on another Olympic champion, Kaylee McKeown, as she split 29.14/29.98 to place second to McKeown (58.49) in the 100 back (59.12).

Next month in Budapest it’s no secret that O’Callaghan will be a force to be reckoned with. And if we’ve learned anything from the way she swims her races, no one lead is safe.

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1 month ago

does this include relay splits? Since I assume the back half would be relatively unaffected by relay starts

Reply to  jeff
1 month ago

Relay splits don’t count as there are other aspects that influence the back half.

Konner Scott
1 month ago


1 month ago

26.57 is insane for a female!

Reply to  WhatIDo
1 month ago

its just insane

1 month ago

If she brought it back any faster she would’ve been splitting the water molecules

1 month ago

So you’re telling me no one has ever tried going out in a 30 and coming home in a 25 or a 26 flat?

Last edited 1 month ago by yoo
1 month ago

Kinda surprised no Cat Campbell on the list.

Reply to  2Fat4Speed
1 month ago

C1 almost always dies in the last 20 metres of her individual 100 free races (just rewatch the 100 free at olympics last year)

Reply to  yoo
1 month ago

and 2016 lmao

Reply to  dddddddd
1 month ago

So you are the sort of person who laughs at other’s misfortune? I feel sorry for any of your friends/family/workmates.

Fraser Thorpe
Reply to  2Fat4Speed
1 month ago

I had the same thought – at her peak, she really set herself apart from around 60-80m, and she’s so strong at the end of her monster relay splits, thought she’d at least be in the top 10.

Especially when kromowidjojo is on the list, and I always thought her best swims were based off her first 50 top end speed and ability to hang on.

Reply to  2Fat4Speed
1 month ago

Campbell almost has the WR in the 100, and most certainly some of the fastest opening 75s ever, but definitely not among the fastest second 50s. Her final 25 is usually lackluster.

Last edited 1 month ago by swimfast
1 month ago


About James Sutherland

James Sutherland

James swam five years at Laurentian University in Sudbury, Ontario, specializing in the 200 free, back and IM. He finished up his collegiate swimming career in 2018, graduating with a bachelor's degree in economics. In 2019 he completed his graduate degree in sports journalism. Prior to going to Laurentian, James swam …

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