After the death of Chad at 2007 Chicago Marathon I talked with my Physician Friend Dr. Daniel Mbithi M.Med. He described to me what happens to the average runners body during a full marathon.
0 – 30 mins (3.25 miles) Body heat and heart rate rises.
In the first half hour of the race, the heart rate of marathon runners climbs to about 140 beats per minute. The average resting heart rate is 75 beats per minute. If you are healthy and have done plenty of training you should find this easy.
Your normal body temperature starts at around 37C, this will climb to around 40c. The hotter the weather, the hotter you will be. By now your body will be sweating like a pig. Sweating is a good thing because its the body natural mechanism to cool the body.
30mins to 1hr. (6.5 miles) Comfort zone.
Now, running will be easy. The heart rate will be steady 135 beats per minute. The body will be relying on carbohydrate fuel, in the form of glycogen manufactured by the liver.
This will be the point when most runners will start feeling thirsty. You will need to visit the water point for some fluid.
1 to 2 hrs (13 miles) Burning fat
Store of glycogen will be running low and your body will now start to burn fat to power the muscles. You will also feel more thirsty.
A runner must make sure he gets regular drinks to stop himself becoming dangerously dehydrated.
2 to 3 hrs (20 miles) lactic acid build up
This is the point most runnners hit the so called wall. The body’s glycogen stores are now exhausted and the muscles must rely on the breakdown of fat. I remember at my first marathon the 30K mark was the point when I started going down hill. I felt sore and pain in my feet.
In some cases , you may suffer stomach cramps due to the fact that oxygen-rich blood has been diverted away from the digestive system to the muscles.
Runners who have not trained properly can start to experience difficulty breathing and there is too little oxygen reaching the muscles.
By the end of this period glycogen levels have bottomed out so blood sugar levels are very low. Blood sugar is needed as fuel for the brain, so you can feel fainty and cloudy. Some runners get mentally exhausted.
You also start to go into anaerobic respiration. One of the by product of anaerobic respiration is lactic acid, which causes pain and muscular cramps.
The joints, particularly the knee caps and ankles will be sore because they are under pressure from the pounding of the hard tarmac.
3 to 4 hrs (the final stretch) Exhaustion point.
If you have survived the last stage, then you might just make it to the finish line.
This is the point where people at risk may suffer from heart attacks, because the heart is under maximum stress.
Dehydration is also more likely, which thickens the blood and slows down the circulatory system. This means the heart need to work harder than normal to pump the thick heavy blood.
Your body is now reaching exhaustion point and a runners pace has usually slowed right down.
The home stretch (finish line here I come)
If you have gotten this far, clap your hands and say ooh!
You will be exhausted and in pain from injuries or soreness. Remember seeing the limp of Lance Armstrong at the finish line of 2006 New York marathon? Even exhausted runners will push themselves to the limit at the last to try to make it to the finish line
Have a Safe Run!