What Does a Backpack Chest Strap Do?

It keeps the shoulder straps in place, reduces sway and changes how the weight is spread across the chest and shoulders.

Published October 28, 2026 · 3 min read · Topic: Size, Fit & Comfort · Size & fit

Typical situation

Your backpack has a thin strap across the front that you usually leave unclipped, and your shoulder straps keep slipping.

Main answer · berabags Editorial Team · Fit view

It keeps the shoulder straps in place and reduces swaying. The NC State Ergonomics Center says the primary purpose of a sternum strap is to relieve pressure on your shoulders and spread the weight across the chest.

What the source says

The primary purpose of a sternum strap is to alleviate pressure from the shoulders and distribute the weight evenly across the chest.
A chest strap helps keep the shoulder straps in place and reduces swaying of the pack, while providing comfort and stability.
It changes how the weight is distributed across the chest and shoulders, for better load management.
Packs designed for higher weights may have shoulder, waist and chest straps, while lightweight packs can have two shoulder straps.
For carrying a laptop bag from place to place, two shoulder straps are most efficient.

How to use a chest strap

Put the pack on and adjust the shoulder straps.
Clip the chest strap across the chest.
Slide it to a comfortable height.
Tighten it until it is snug but does not restrict breathing.
Move around to check that the shoulder straps stay in place.

When it helps

When the pack sways, when the shoulder straps slip, or when you are moving quickly, such as on stairs or a bike.

A fitting hint

If the chest strap pulls the shoulder straps inward or digs in, it may be set too high or too tight. Lower it a little and loosen it, then check that you can breathe deeply. If the shoulder straps are very far apart on a small frame, the strap can help hold them in place, but a smaller pack may fit better.

Where this answer stops

This is general guidance from one ergonomics centre. A chest strap is a comfort feature, and your own fit may vary.

Sources and further reading

NC State Ergonomics Center: Backpacks, Shifting the Load to Your Advantage

Three more perspectives

berabags Editorial Team · Fit view

Fasten the strap across the chest at about the height of the armpits, snug but not tight. A strap that is too tight restricts breathing, and one that is too loose does nothing.

berabags Editorial Team · Use view

Use it when you walk or cycle, or when the pack slides on your shoulders. For a quick trip with a light load, you may not need it.

berabags Editorial Team · Purchasing view

Look for an adjustable strap that slides up and down. A fixed strap may sit in the wrong place, which makes it less helpful.

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