Joseph Schooling may be on home ground when he stands on the starting blocks at the OCBC Aquatic Centre tomorrow, but he will be in rather unfamiliar territory.

He will compete in only the 200m individual medley, an event he has not raced in since the 2015 SEA Games, during the Aug 15-17 Singapore leg of the Fina Swimming World Cup.

For the 24-year-old Singaporean, the race is a "litmus test" of where he stands physically.

"I have a time in mind that I want to go at this meet, and the way I want to feel throughout the race... at the end of the day, I think the most important thing is (that) I need to get my volume up in practice, I need to start doing longer and more sustained, intense sets," said Schooling yesterday.

The Olympic 100m butterfly champion believes incorporating more middle-distance (200m-400m) training, which entails more laps, will help him to regain his form following a disastrous outing at last month's world championships in South Korea.

Not only did he fail to retain the 100m butterfly bronze he had won in the previous two editions, he did not even make the final in Gwangju, clocking 52.93 seconds to be 24th in the heats.

"The IM trains a lot of different things, like fitness and different strokes, and it taps on different muscle systems and energy systems," said Schooling, who set the 200m IM national record of 1min 59.99sec in 2013, as he explained his choice of event for this meet.

"Eddie (Reese, his former coach at the University of Texas, Austin) told me (in 2016) that I need to stay in a middle distance to do well, but middle distance hurts a lot more than a sprint. And so I just wasn't ready for it until this year to keep pushing that middle distance like I had been.

"That's what won me the gold in Rio, and that's why I need to go back to it."

National Training Centre head coach Gary Tan estimates that about 80 per cent of Schooling's training is now focused on training for middle-distance events, up from about 40 per cent leading up to the world championships.

This will benefit Schooling in the 100m fly by giving him more speed in the second 50m so that he can finish stronger, explained Tan.

He told The Straits Times: "We felt there was a need to change it a bit and do a bit more conditioning on the legs, so that's where the middle-distance stuff comes in - we can focus on mileage and the intensity of his kicking sets, but we want to build on it progressively and get him into the best shape possible.

"If you condition your legs and your lungs, there's a lot of good that will come out of it."