Evan Chee is on the treadmill doing what he does best - running.
But this evening workout is no ordinary training session for the 37-year-old marathoner, who prefers to train outdoors anyway.
On the agenda for Chee, who has a marathon personal best of 2hr 42min 18sec, are two tests to measure his lactate threshold and fuel efficiency.
For the first, he wears a heart rate monitor. Five times, during intervals between five-minute stages of successively higher speed, a blood sample is taken from his third finger by fitness consultant Ben Pulham, who measures the lactate levels in his blood.
Lactate is a substance produced by the body in response to aerobic exercise and serves as a fuel for the muscles, delaying fatigue and preventing injury.
The lactate threshold is reached at the exercise intensity when the body is producing more lactate than it can effectively use, such that the lactate is exported to the blood and the muscles start to fail.
"At this point you're just getting slower and slower and the mistake many runners make is to keep training harder," said Pulham, the founder of Coached, a heart rate training programme located in Robinson Road.
Fat calories stored in an average person.
Calories burnt every hour at a marathoner's highest speed (16km/h) during a fuel efficiency test, of which
of calories burnt is fat.
"Most runners look exclusively at pace but you can't push harder forever. Lactate threshold differs between individuals, so knowing yours helps you train at the right intensity to teach your body to become more efficient at clearing lactate."
So while Chee began the test at 12km/h, a comfortable speed for him, and worked his way up to 16km/h, training at 12km/h would not be advisable for most regular runners, many of whom end the test at that speed, Pulham added.
Where Chee is a lot more like most runners is in his diet.
He works long hours in his day job as an engineering manager and admits he rarely watches what he eats after he knocks off.
"After work and a long run I tend to just put everything in my mouth. I don't really control (my diet) that much," said Chee, who is managed by ONEathlete and finished fourth last year in the local men's category in the Standard Chartered Singapore Marathon (SCSM).
These lifestyle choices were reflected in the test of his fuel efficiency, measuring the percentage of fat and carbohydrates or sugars he burns at different intensities.
"Good fat-burning is kind of like a safeguard because our bodies have more fat reserves than sugar and we want to conserve the sugar by burning fat as long as we can," said Pulham.
"Fat-burning is primarily driven by what you eat. Many athletes believe they can eat what they like because they do so much training, but sugar fuel is nowhere near as clean-burning as fat and also slows recovery."
The average person has approximately 1,400-2,000 calories of carbohydrate stored in their body and 50,000-80,000 calories stored as fat.
Runners who are more efficient at burning fat thus need fewer food calories from energy gels during marathons, for example.
During the test, Chee started burning sugar at a relatively early stage, which Pulham said could be improved by eating fewer carbohydrates and more foods with healthy fat such as avocado.
At 16km/h, the highest speed of the test, Chee was burning calories at a rate of 900 per hour, but only 2 per cent of those calories were fat.
He was surprised by how diet determines fat burning, and is keen to tailor his diet. Said Chee: "There is still time before the SCSM so I'm interested to see how adjusting my diet will affect my performance."
The two tests at Coached cost $195 each.
• Registration for the SCSM is still open at singaporemarathon.com