After writing the post about the oldest bikers, my intention was to reflect who were the youngest cyclist in the world. I could not find the answer on the net, so I am going to explain a little about the process a lot of us have experienced with great pleasure.
Learning to ride a bicycle, a two-wheeled bike without training wheels, mostly occurs sometime between the ages of 3 and 8 (although some adults learn it because they did not have the opportunity when they were young, and fortunately, people do not forget how to ride). The average age is 5. Indeed, most kids just learn when they are ready if their families can provide them with bikes. Curiously, a systematic review found that children who started biking at ages between 3 and 5 suffer higher injuries than those who were 3 to years old.
Sliding the 3 to 5 group, kids between 3 and 4 years are in significant gross motor skills development. For example, they learn to balance on one foot, walk on their tiptoes, climb, hop and skip. A 3 years old child can pedal, use a handlebar and ride a tricycle, but she does not have the balance required to ride a two-wheeled bicycle. Better, she can ride a bike with training wheels and after she dominates it, increases coordination and muscle, move to a bike without training ones. It is a good idea use foot brakes instead of hand brakes in this age group.
Regarding the 4 and 5 group, these children are ready for two-wheeled bicycles. Most 5-year-old kids have balance and coordination enough to ride a bike without training wheels. However, they might not understand the risks of riding near traffic or without paying attention to crossings. Then, adult supervision is required to avoid falls and injuries.