Preheat oven to 425°F (220°C).

Spray 12 muffin tins with baking spray.

In a large bowl, combine oats, whole wheat flour, Splenda, baking powder, salt, and cinnamon.

In a separate bowl, combine milk, egg, and applesauce, and vanilla extract.

Pour the wet ingredients into the dry ingredients and gently fold until just combined.

Fold in blueberries and chopped walnuts.

Fill each muffin cup 2/3 full.

In a small bowl, mix together sugar and cinnamon.

Sprinkle the cinnamon-sugar mixture over the top of each muffin.

Bake for 20 minutes, or until a toothpick inserted into the center comes out clean.