For Sofie Chandra, 32, completing a 10km race in tomorrow's Standard Chartered Marathon Singapore (SCMS) will be "quite a struggle".
However, the marketing manager at nightclub Zouk is determined to clock her best timing yet - all for a good cause.
"When I run, my ears often become blocked," explained the member of the High Panters, a local running group who are raising funds and awareness for the Alzheimer's Disease Association Singapore as part of a year-long charity project.
"This is not only uncomfortable but also affects my race as I am not able to hear my breathing and pace myself."
Founded in 2012 by her boyfriend Eugene Lim and two other friends, the High Panters have been supporting a charity every year.
Former charities include the World Toilet Foundation and Hope for the Family Thailand, an educational facility in Chiang Mai.
Set up as a way to promote running while giving back to the less privileged, the High Panters count some heavyweight social influencers in their ranks. Local TV actress Shine Koh and Instagram celebrity Audrey Goh are members.
This year, the group of 25 running enthusiasts have taken part in various events to raise awareness for the Alzheimer's Disease Association. A donation page they set up at the online fund-raising site, GIVEasia, has raised about $4,000 so far.
With donations matched dollar for dollar for the SG50 year, that amount is set to double.
The SCMS will be the group's final charity event for 2015.
High Panters founder Lim, 35, is the head of marketing at fashion retailer Toscano.
He will also be in the 10km run. About 10 High Panters members will be taking part in various races tomorrow.
He said that the group always selected a less-known charity to support as it was likely to benefit more from both the money and awareness raised.
For Chandra, supporting the association is a cause that is close to her heart. She said: "My grandmother has been suffering from Alzheimer's for a number of years now, and it is still sad for us as a family to see her deteriorate.
"Earlier on, when her condition was not that serious, she was able to recognise me but unable to differentiate between my two brothers.
"Now, she no longer recognises any of us at all."
To prepare for the race, she has been training with Lim about thrice a week, including a run every Sunday with other High Panters.
Lim, who studied sports science, said he designs training plans for himself and Chandra but sticking to them can be difficult.
"It is the holiday season now, so we are both very busy.
"But we are still trying to follow it as much as we can," he said.
Come Sunday, Chandra is aiming to better her personal best of 1hr 9min set at last year's race.
Blocked ears or not, nothing is going to block this runner from going all out.
" I am determined to do my best," she said.