Climbing Mt Kinablau via the Timphonon route (the easiest) was a fairly vigorous effort for the two of us who trained for only a couple of weeks leading up to the climb and were sick with colds during the climb, but the reward of seeing the sun RISE from the summit was more than 100% worthwhile. And of course there's simply nothing like knowing (and being able to boast) that we've conquered Mt Kinabalu, the highest peak in Southeast Asia.
To be fair, the climb itself, and packing sensible equpment, is about all we can claim credit for. Park authorities (and your RM) provide little luxuries that you normally don't expect on a hike: a patient and humourous Kadazhan mountain guide who kept me from falling off the mountain, tidied pathways often with steps/ stairs/ safety ropes, rest pavillions with flush toilets/rubbish bins, and perhaps most surprising of all, a warm comfortable overnight stay at Laban Rata - complete with freshly laundried sheets and towel (!!!), tasty buffet meals, clean bathrooms, a snacks/drinks store... you can even get a porter to carry your gear, but we thought that was just going too far.
So my advice for other not-so-fit climbers is to
1. Train as much as you can. I suggest lunges and stairs. The fitter you are the less likely you'd struggle or have an accident. If you're healthy and determined enough you'd still get there eventually, but allow more time esp for the summit climb if you don't want to miss the sunrise. It took us 6hrs base-LR, 3 hrs LR-summit, 2hrs summit-LR, 4.5hrs LR-base.
2. Invest in the right gear. You need to stay cool enough for the lower half and warm enough for the summit climb. Pack minimally - I think anything more than 5kg is too much. When you're exhausted and looking up at yet another unending flight of steps, each kilo feels like a hundred more.
3. Start the climb early on Day 1. This allows more time to rest at Laban Rata and avoids climbing during the heat of the day.
4. Unwind in the hotsprings (or at least a hot jacuzzi) after the climb. Get a gentle massage too, its cheap in Malaysia.
Packing suggestions.
1. Lightweight hiking backpack with raincover.
2. You wear: lightweight breathable top and pants, waterproof hiking boots, socks, cap/ sunnies, sunscreen, sports watch (if you want to keep track of time).
3. You pack: camera with spare battery (it seems to die quicker up there), 1L water in a water bladder, energy bars, first aid kit (painkillers for headaches due to altitude sickness), sunscreen, waterproof hiking jacket (or plastic poncho), headtorch, wool socks, merino wool base layer top and pants, lightweight mid layer fleece jacket, beanie, waterproof ski gloves (in case its wet), thin gloves/ liners (in case its dry), energy drinks eg milo, toilet tissue, toiletries (you may not be able to have a hot shower at LR due to electricity shortage).
4. Walking stick. You can get a simple wooden one at Kinabalu Park for RM3. It really helps.
5. Sutera provided a packed lunch for the first part of the climb. It consists of a 500ml bottle of water, an apple, plain sandwiches, a piece of fried chicken and 2 hardboiled eggs. If you get the same thing, I'd suggest that you have the chicken for breakfast unless you fancy a cold soggy chicken later on. Dump the big plastic box and pack the sandwiches/eggs in ziplock bags that are easier to carry. Ziplock bags are the best friends of hikers!