Banana Muffins w/ crumb topping

I had bananas I needed to use up and I found this recipe at All Recipes. I made changes to make them lower in fat and calories. My family ate these moist muffins up can't wait to make them again soon.

1 1/2 cups all-purpose flour
1 teaspoon baking soda
1 teaspoon baking powder
1/2 teaspoon salt
1/8 teaspoon ground cinnamon
3 bananas, mashed
1/2 cup splenda
1 egg, lightly beaten
1/3 cup applesauce (no sugar added)
1/2 cup toasted walnuts or pecans (optional)
1/2 cup chocolate chips (optional)
1/3 cup packed splenda brown sugar
2 tablespoons all-purpose flour
1 tablespoon light butter (very cold)

Preheat oven to 375 degrees. Lightly grease 10 muffin cups (I use Baker's Joy) and set aside.

In a large bowl, sift together 1 1/2 cups flour, baking soda, baking powder, cinnamon and salt. In another bowl, beat together bananas, splenda, egg and apple sauce. Stir the banana mixture into the flour mixture just until moistened (do not over mix). If adding optional ingredients fold in once batter is mixed. Spoon batter into prepared muffin cups.

In a small bowl, mix together Splenda brown sugar and 2 tablespoons flour . Cut in 1 tablespoon butter until mixture resembles coarse cornmeal. Sprinkle topping over muffins. Bake in preheated oven for 18 to 20 minutes, until a toothpick inserted into center of a muffin comes out clean.