They scale a 1.5m-high wall, hoist themselves up a 3m-tall rope and get up from a prone position to dash 50m at the blow of a whistle.
They are then thrown into a series of rapidly developing terrorist scenarios, and have to contain the threats quickly.
This is just a small part of what elite officers from the police Emergency Response Teams (ERT) are put through every 10 weeks.
Last Friday, The Straits Times had the rare chance to train alongside the officers during their session.
About 30 officers gathered at 9am in an abandoned school building in Upper Thomson Road, which is now used as an urban training facility.
After a quick round of exercises to hone their agility, speed and reaction, they took turns to run through scenario-based drills.
These include tackling a armed gunman who was holding four people hostage in an empty classroom on the second floor.
Gunshots rang out from an adjacent building, as other officers did shooting exercises.
Whether in training or in the field, ERT officers have to don about 17kg of gear, including bullet-resistant helmets and vests. They are also armed with HK-MP 5 sub-machine guns, which boast a greater range and hold more ammunition.
It was announced in April last year that a dedicated fast-response police unit - the ERT - would be set up to form the first wave of responders to a terrorist attack on Singapore shores.
The unit's officers were handpicked from the six major land divisions, and equipped with tactical and counter-assault skills.
The first batch of ERT officers was commissioned in June last year and have since hit the ground running. They train regularly with officers from the Special Operations Command to ensure they are in tip-top shape.
Assistant Superintendent Fionie Chan, 34, said: "The threat is real... And we have to be fully equipped to deal with all kinds of attacks."
ASP Chan, a team leader of the Central Police Division ERT, leads a team of four to five officers in high-visibility patrols in the Central Business District and surrounding areas.
They are on their feet with their heavy gear for most of their 12-hour shift, but "we push each other on, because we know that patrols are a deterrent as well", she said.
The patrols also allow them to familiarise themselves with the terrain, she added.
While female ERT officers are a minority, with only one or two in each division, ASP Chan said there are "no shortcuts or concessions" for them.
On her own initiative, she has also gathered her team to undergo exercise drills and runs, or to plan tactical strategies on their days off.
"When we train hard, we fight easy," she said.
