Financial controller Chua Wai Kuen, 49, used to push herself at HIIT or high-intensity interval training sessions three times a week.
Little did she know that her last HIIT session would take place in September 2013.
She was in class, sweating it out when all of a sudden, she heard a snapping sound and felt a sudden pain in her head.
"It was like a rubber band breaking in my head. The pain was extreme. You will not confuse it with a typical headache or migraine. It was distinctly a kind of pain I had never experienced before," she said.
"You can feel the paralysing feeling moving down your spine. You feel immobilised and you have to lie down. My fingers were curling up and I was in cold sweat."
She suspected she had a brain aneurysm which had ruptured.
Quickly calling out to someone at the gym to call an ambulance, she blacked out. "I actually told him 'aneurysm, aneurysm', but I think he didn't understand it."
Dr Tang Kok Kee, who attended to her at Gleneagles Hospital said Ms Chua's case was a "good grade SAH (subarachnoid haemorrhage)". These are the people who are still conscious when they arrive at the hospital."
SAH happens when a brain aneurysm ruptures without warning, causing blood to flow into the space surrounding the brain or the subarachnoid space. It can lead to coma or death.
Ms Chua had blacked out but only for a while. An X-ray of the blood vessels of the brain was done to confirm the site of the aneurysm.
Surgery was then performed and the neck of the aneurysm was sealed off with a clip.
Ms Chua said she was up and about within two weeks. She went back to work and life, though for a few weeks, things weren't the way they used to be. "I felt my right ear was very sensitive to loud noises and my vision couldn't adjust to too many movements in front of me. I certainly couldn't go shopping in a crowded store," she said.
She also lost stamina.
Now, things are back to normal though the bachelorette has made some changes in her life.
"I think I pushed myself too hard and overexerted myself at that HIIT class," she said. "I don't do HIIT exercises any more. I can't even do yoga as there are some poses... that I don't feel comfortable with. I can feel some light pressure building in my head when I do those."
Instead, she just takes walks.
"I take things easy because I still have another aneurysm. It's small and not ruptured. I go for check-ups every 1 ½ to 2 years to monitor it," said Ms Chua.
"I don't carry heavy stuff and I do not overstrain myself mentally with long hours of computer work. I am conscious about not feeling mentally and physically stressed."