Yams have a very low GI and slow even release. I suppose that would help to allow more of the glucose to be stored in the muscle bellies.
I LOVE YAMS...
Here is my favorite recipe:
10 oz yam
Microwave for 12 minutes. Peel the skin and place in bowl, add 2 packets of splenda, teaspoon of cinnamon and some low fat milk.
Whip into a frenzy until it looks like pudding.
Tastes like pumpkin pie...