Preheat oven to 175 degrees Celsius (350 degrees Fahrenheit) and grease a 12-cup standard muffin tin or use silicone liners.
In a large mixing bowl, mash the ripe bananas until a liquid consistency with minimal lumps is achieved.
Incorporate the Greek yogurt, egg, maple syrup, and vanilla extract into the banana mixture, whisking until the wet base is fully emulsified.
In a separate bowl, whisk together the whole wheat flour, vanilla whey protein powder, baking soda, cinnamon, and salt to ensure even distribution of leavening agents.
Gently fold the dry ingredients into the wet mixture using a rubber spatula until just combined; do not overmix as this will toughen the crumb structure.
Portion the batter evenly into the 12 muffin cups, filling each to approximately three-quarters capacity.
Bake in the center rack for 18 to 22 minutes, or until a wooden skewer inserted into the center of a muffin comes out clean.
Allow muffins to cool in the pan for 5 minutes before transferring to a wire rack for complete thermal equilibration.