Great Ocean Road Marathon 2007: Physiology, running, and recollections…

Hi all.

En route my preparation for the Great Ocean Road International Marathon 2007, i came across things that i came across before, but never really deliberated about. I guess i wasn’t a medical student then, so wasn’t sooo interested in the physiology and nutrition side of things.Nonetheless, here they are in bold italic headings.

GIT physiology

I have only heard about and practised them according to advice previously, and never really questioned further and was pleased with the fact that carbohydrate-rich foods will help. I mean, i did learn bits and pieces of biology with regards to digestion and absorption. Simple stuff… like dietary carbohydrates are digested to monosaccharides and absorbed in the small intestine. Anyway, i will seek to update this post along the way.

Carbo-depletion

Carbohydrate depletion, apparently is a method used by long distance runners / ultra marathoners. A discussion goes on here at Kevin Sayers’ UltRunR Website about how it works, whether it works, etc…

Carbo-loading

“Runners used to just be concerned with getting enough carbs,” says Lisa Dorfman, R.D., a sports nutritionist in Miami. “Now we’re taking it a step further and looking at which carbohydrates are best for us.”
- From “The Whole-Grain Truth”, Runners World

From what i know from common knowledge, bananas, potatoes, spaghetti, rice, were what my coach and brother used to recommend.

In case any runners stumble upon this blog post, do note: work out what is best for you. Do not try something new before a race. Do something that you are tried before. This applies for training plans as well.

Dehydration

Acute dehydration results in decreased plasma volume, cardiac output, and arterial pressure which leads to a lower firing rate of baroreceptors. Plasma osmolarity increases, because more water than salt is lost in sweat. The increase in plasma osmolarity leads to increased ADH secretion. High plasma ADH levels causes increased water permeability of the collecting duct cells. Therefore, more water is reabsorbed by the kidneys and renal water excretion is low. Basically, you make less urine to conserve water. (the above will barely scrap a pass for a short answer question that asks “What happens in acute dehydration?”, you think?)

Thirst

Thirst, a function to replace fluid loss, is triggered by 2 stimuli, namely (1) dehydration and (2) decrease in blood volume.

Both of which surely happened to me, and many other runners, and we definitely appreciated the water stops along the way, placed at perhaps 5-6km intervals. Massive littering took place after the water stops, and it just seems people can seem to bother to aim and throw the water bottles and cups into the bins provided.

While there were no sponges, (probaby since it was cold, and windy, no sweltering heat to warrant sponges), the scenes i saw at each of the water stops look starkly similar to the one above.

Oh, and the GOR marathon runners wore more.

Back to the point of how thirst is triggered,

(1) Dehydration –> Thirst

• Decreased ECFV –> osmoreceptor cells in hypothalamus shrink –> these signal the cerebral cortex –> sensation of thirst
• Reflex decrease in salivary and buccal gland secretions –> dry mouth and throat
• The above is a very sensitive mechanism and it only requires a 1-2% change in plasma osmolarity to be initiated, thus stimulating thirst.
• Isn’t it wonderful how our body works?

(2) Decrease in blood volume –> Thirst

• The lowered blood volume stimulates baroreceptors and strectch receptors (atrial and pulmonary).
• Thirst control centres in hypothalamus stimulated –> thirsty sensation
• This is a mechanism that is less sensitive than the one above. A 10 - 15 % change in blood volume is required to stimulate thirst.

My experience at Great Ocean Road Marathon 2007

While this is long overdue, i feel its worth noting. I watched Man Utd lose in an highly un-entertaining FA Cup Final to Chelsea FC, and it was already 2 a.m. here in Melbourne. Then i prepared to go, left near 3a.m. and drove with Eliot, a fellow medic from Monash. We had a little trouble initially, losing our way, torn between whether to follow Google Maps directions or Melway. That was humiliating but we were glad to finally hit M1 expressway. But ALAS!!! we found the tunnel further down that we were to use was blocked off and we had to take a detour. Nevertheless, EVENTUALLY, we reached Apollo Bay in due time a little just over 6 a.m for the shuttle buses to bring us to the 23k start point. There, we eased ourselves, and i regretted not emptying my bowels, as you shall read later. I didn’t want to miss the flag-off!!

The race started at 8a.m. I must say the views were fantastic at times. Too bad i didn’t have a camera to capture it. but it will always be lodged in my hippocampus (long-term memory), and probably will be reinforced every year i go back there for this wonderful race, which brings me to the point that the hippocampus is not the only structure involved in long-term memory.

That’s Eliott and I below. Smiling at the camera-man deliberately.

Losing heat

It was cold. Probably about 15 degrees celsius.It was sunny, but the wind chill factor was there. I am not a mountaineer, i cannot estimate wind chill factors.

Hence, i was wearing my windbreaker.

Blisters and regrets

I crossed the official half marathon line at 2hrs 3min. I was absolutely drained. I had pushed too hard early on with eliott, averaging a 5min per kilometre or less. I was with him till about 10 - 11km, and then he pushed ahead. I continued at a steady pace of 5:00 - 5:30 per km, and made good progress till about 16km, which is when things started happening. I regretted my choice of not taking a poop at the start line toilets. I regretted wearing my racer which did not offer enough cushioning, as i could slowly but surely feel the blisters forming.

This is the closest i could find and the mildest one for display on this family-oriented blog. Except that my blister was posterior to the ball of my right foot and had more reddish fluid in it. I made the stupid mistake of bursting it and then using the nail-clipper to clip away the dead skin after, and that exposed the underlying tissue, which delayed my healing for up to 3 weeks. (I did apply antiseptic iodine solution daily, but you can imagine the ball of the foot is a highly mobile area, especially when i dorsi-flex my foot in a normal gait.)

Relief

(PHOTO OF ME FINISHING WILL BE UP SOON)

It felt so good. I received a finisher’s medal. I was directed to a seat where a lady undid my shoelaces to take out the computer chip for tracking my time. I gulped 2 bottled of fruit juice down shortly after i made my way to the gift pack counter.

Eliott met me and we stayed around to check out the finisher of the 45km marathon event. Kenyan, as expected.

It felt good to cheer people on as well! I did that along the way, as we made our way to my rented car to change before heading back to a nice meal of “fish and chips”. Greek chefs. original fish and chips. excellanto!

the appetite for another half marathon lingers. and the dream of a marathon still strong.