Believe it or not, there's been a lot of research regarding flip-flops. A recent study found that flip-flop wearers tend to grip the footwear with their toes, causing shorter stride length and improper force when their feet hit the ground.
7 Types of Sandals that Cause Serious Foot Pain – Taos Footwear
Why Birkenstocks Aren't a Long Term Solution to Foot Pain
Why Are Flip Flops Bad for Feet - footsurgeon
Why Runners Shouldn't Wear Flip-Flops - The New York Times
The Real Dangers of Flip-Flops
Possible Foot Pain May Come from Wearing Flip-Flops
Are Flip Flops Causing Your Foot Pain? - Dr. Atencio
Are summer shoes causing your foot pain?
How To Stop Sandals From Making Suction Noise – Solethreads