My experience in swimming
I have already done a lot of blood sugar tests during the swim in the past. I always struggled with stomach cramps after the swim during a race and this is probably related with the fast drop in my blood sugar level during the swim. Here you can read my story how I figured out how to get a stabile glycemia during a 4k swim.
(1) How I began:
On 16, 20 and 22 May 2011 I had 3 test days. On these 3 days I had the same breakfast taken on the same time and I started swimming at 12AM.
On Thursday 16 May I eat 150gr of dried grapes and 600mL of isotonic sportsdrink of Etixx between 10-12AM. I aimed to get a high glycemia before the start of the swim and I hoped the sugars of the dried grapes and of the sportsdrink will be released graduately into my blood during the swim. This should result in a stabile glycemia. But the result went out differently. Within the first km my glycemia dropped from 196mg/dL to 127mg/dL, and after de second km to 88mg/dL. This drop is too rapidly in my opinion. Unless I felt OK, and the running and cycling afterwards went really well that day.
Mondag 20 May I did everything the same except eating 1 Etixx gel right before the start of the swim. I hoped this would result into a slower glycemia drop. Unless I eat the same before the swim my glycemia was just 117mg/dL. After 1km swimming my blood sugar level went down to 80mg/dL and after 1.5km 71mg/dL. After the swim, I struggled with stomach cramps.
Wednesday 22 May I eat 250grams of dried graves between 10-12AM. And 30minutes before the swim I eat 4 slices of bread. Again my blood sugar level dropped really fast already after 1km swimming.
During the swim my body is able to stabilize the blood sugar level between 70-85mg/dL. I will not get a hypoglycemia during the swim. I’m burning too much energy during the swim resulting in a fast drop in my blood sugar level. Because I’m doing a physical activity, my body will be searching for energy somewhere. My body is noticing I’m getting a hypoglycemia and will react to this breaking down muscle tissue for example to get energy from. This will prevent my from getting a hypoglycemia during the swim, but I will get stomach cramps afterwards. (2)Final result: I figured out eating pancakes is really good to have a stabile glycemia. During Ironman races I eat 300grams of pancakes 2 hours before the start of the race. In the last hour I drink isotonic sportdrink from Etixx and in the last 30min before the race I eat 200grams of pancakes. This will result in a relatively high glycemia of 160-200mg/dL. A few minutes before the start I eat a isotonic SIS gel. The fast and slow sugars into the pancakes and SIS-gel will result in a stabile glycemia between 100-120mg/dL. Half way of the race, after a 2k swim, I eat another SIS-gel to keep my glycemia stabile. If I’ll not eat a second SIS-gel, my blood sugar level will drop really fast after the second km because the fast sugars of the pancakes and the first SIS-gel are already burned.