SINGAPORE - National marathoner Soh Rui Yong has gone from struggling with a troubling foot injury just months ago to a new personal best.

The 2015 SEA Games champion clocked 2hr 24min 55sec at the Chicago Marathon on Sunday, eclipsing his previous best of 2:26:01 from the California International Marathon in 2014.

The timing means he has easily met Singapore Athletics' qualifying criteria for next year's SEA Games in Kuala Lumpur, where the 25-year-old is hoping to become the first marathoner to retain his title at the biennial event.

It is also the closest anyone has gotten to M. Rameshon's 1995 national record of 2:24:22.

Soh's previous best was also the second fastest, until his latest endeavour in Chicago, where he finished 32nd among the men and 37th overall.

Soh, a University of Oregon graduate, has been training in the United States. His training in the last few months in particular have been done at high altitude, with a two-week stint in the mountains of Mammoth Lakes, California, before spending two months at Flagstaff, Arizona.

A plantar fasciitis injury - tissue inflammation at the bottom of his left foot - has hindered much of his progress and training since last November. He pulled out of the Fukuoka International Open Marathon Championship late last year.

The injury was aggravated when he competed at the World Half Marathon Championships in Cardiff in March. He completed the London Marathon in April in 2:37:33, way off the 2:19 he needed to clock to qualify for the Olympic Games in Rio de Janeiro in August.