Flat PedalsAt first, pedals were flat. They are effective and still used today.
Pedals with Toe Clips
Then, to get better power transfer, riders used toe clips and straps to secure their shoes on the pedals. The problem was that, to get your foot out when coming to a stop, you had to first loosen the strap.
We hope this helps! If you have any more questions, let us know.
Photo Credits: "Fahrradkram" by Ralf Roletschek is licensed under CC BY-SA 3.0 (cropped from original). "Bicycle pedal, quill type, early 1980s, Campagnolo SL road" by LDHan is public domain.