There are two kinds of lumbar belts on backpacks:
- load bearing belts;
- just a strap (similar to the chest strap), used only to stabilize the backpack.

The first type is essential and should always be used, but those backpacks are intended for hiking/trekking, not for carrying on the back while riding a bicycle.

The use of the second type is optional. This type is usually found only on small backpacks (including backpacks designed for bicycle riders).