There’s a blue line that runs round Centennial Park if you care to examine the tarmac closely. It’s broken and scrubbed out in places but for me it’s at least as much a Sydney landmark as Centrepoint Tower. If you’re a serious tarmac archaeologist you’ll still find traces of it on the Harbour Bridge tracing out a racing line into the Cahill Expressway. It’s the marathon line from the 2000 Olympics and it’s no accident the Sydney marathon follows much of the same route, since it winds through some of the most picturesque views you’ll find in any city anywhere.

Certainly today at the 20km mark, when the initial excitement of running the bridge and up the fig tree avenue through Hyde Park past the ANZAC war memorial has faded and the little voice in your head is doing the maths (“not yet half way!” – shut up little voice!), it’s a boost to lock onto the blue line and know that you’re running a marathon following the same steps as Olympic gold medal winners. Their race was different to mine though. For a start they were home and hosed an incredible two and three quarter hours before me (yes, little voice, they could have run the full race, turned around and run back to the start and still have beaten me). It’s a certainty that their race plan would have looked very different to mine.

My plan was pretty simple: eat like a horse the day before, get a long glass of hydration salts and some muesli squares down the chute for breakfast, and then when the gun goes off, settle into a nice steady pace – with a forecast top temperature of 28 degrees, it was no time to be a hero. The plan went pretty well to 25km, on the long low incline from Anzac Parade back up to Oxford Street. It pretends it’s flat, but it lies… one look at the superhuman effort the Wheelies need to put in shows they’re not coasting that stretch – my hat’s off to those guys. It’s a big effort, especially baking in the sun.

The sun was the problem. Each kilometre under the glare draws more salt from you, and you have to put it back somehow. The body is a machine, and if you don’t put liquid and electrolytes in, it will grind to a halt. Get the balancing act wrong and you are in trouble, like four fellas I passed flat out on the tarmac with an ambulance team pumping IV fluids in through a drip.

I was flagging as I hit 30km and met up with the family support crew waving a wonderful handmade sign. I picked up an icy Powerade and the iPod with the running tunes pre-loaded. Earphones normally bug me when running, but this time it was like a super power boost: recharged with great tunes to thump away the distance. But trouble was looming and at 34km I hit massive cramps in my calf muscles. Cramps are usually the result of nerves misfiring because they don’t have the usual levels of sodium, potassium and magnesium, causing the affected muscle to lock up tight. All of a sudden it looked like the race was going to get away from me.

Through the Pyrmont dog leg, I was reduced to running 200m, stopping to stretch the muscles out and repeating: agonisingly slow progress. Walking helped, but would mean that a 4:15 pace would become a 5:15 pace. I looked at the watch and noted that with 4km to go I would have to somehow find a way to keep running if I was to get in under the 4:30 target time. So it was run, cramp, stretch, repeat all the way, locking up twice on the final 500m through Circular Quay with the seconds running down to the 4:30 target. In the final stretch, with 100m to go and 30 seconds left I made a dash for the finish, cramping up badly three metres after crossing the line. And my time? 4:29.45.

Maybe the marathon is too much work. Maybe you can build up for three months through the cold and the rain and then still have something unexpected cripple you within sight of the finish. Maybe you step up to the start line and roll the dice that decides whether it’s you with the IV drip on the floor. But you’ll also find out more about yourself than you ever will at yoga. Will I run another one…? My legs say no. But what do they know? Maybe.