Ashis Roy, 81, clips 20 minutes from his timing

India's marathon man Ashis Roy, who has run 115 full marathons, shaved off twenty minutes from has previous timing as he completed his 16th half-marathon in the Whitby Waterfront race in Ontario, Canada.

Clocking a time of 3 hours, 17 minutes and 42 seconds, the 81-year-old cardiologist, the oldest of 200 participants in the race Sunday, clipped twenty minutes from his last run in the San Francisco marathon in June.

Roy, who switched over to half-marathons after a spinal injury in November 2011, said he seems to have fully recovered as he did not use any protective knee caps or spinal support and yet improved his timing.

Lot of people cheered Roy with 100 marathons printed on his tee shirt as he participated in the half marathon race along the picturesque Lake Ontario waterfront on a beautiful balmy day under clear blue skies.

Roy, a resident of Delhi's Chittaranjan Park, who ran his 115th marathon in Mumbai in January, is a retired wing commander of the Indian Air Force.

He took to running marathons at the age of 52 and by 75 he had completed 82 races. He went on to complete his 100th marathon in January 2010.

Roy plans to participate in the Rock 'n' Roll Philadelphia marathon with his 41-year old daughter on Sep 15.