Sitting on a fork and lying on a fork refer to the different ways of crossing the middle part with your legs when riding a bicycle. Their differences are as follows:

1. Sitting on the fork: Sitting on the fork is a common riding posture and a traditional riding mode. In this way, the cyclist's legs cross the seat from the rear and are placed on the left and right sides of the bicycle to form a cross posture.

2. Crouching fork: Crouching fork, also known as recumbent riding or recumbent riding, is a relatively new riding mode, mainly used for road bicycles and competitive bicycles. In this way, the cyclist's legs lie on the seat from the front and are placed on the left and right sides of the bicycle respectively, forming a posture of lying on the cross.

Main differences:

Posture: Sitting fork means that the rider straddles the saddle in a sitting position, and lying fork means straddling the saddle in a prone position.

Applicability: Sitting on a fork is suitable for daily riding and leisure riding, and is common in city riding and bicycle travel. The fork is suitable for long-distance riding and competitive riding, which can improve aerodynamics and speed.

Which way is more suitable for you depends on your personal preference and riding purpose. It is important to ensure that the riding posture is comfortable and stable, which meets the requirements of personal health and safety.