By Dana Okoro, Editorial Reviewer · Published September 14, 2026, 6:03 PM ET · Updated September 29, 2026, 6:16 PM ET
Direct Answer
Position the sternum strap across the upper chest, roughly one to two inches below the collarbone, sliding it along its webbing height track to the right spot for your torso. Buckle and tighten just enough to stop the shoulder straps from splaying outward, while still allowing full, unrestricted breathing.
In plain English
The sternum strap is the small strap that clips across your chest, joining the two shoulder straps. Adjusting it takes two quick steps: slide it to the right height, then set how tight it is.
For height, move it along its little track until it crosses your upper chest, a short way below the bony ridge at the base of your neck. It should not touch your throat, and it should not sit low on your ribs.
For tightness, clip it and pull just until the shoulder straps stop sliding outward. You should be able to take a big, deep breath without feeling it squeeze. Think of it like a seatbelt that is snug but not pressing on you. If it feels tight on a steep uphill, loosen it a little.
The sternum strap connects the two shoulder straps across the chest, and correct adjustment comes down to two separate settings: height on its webbing track, and tension once buckled.
Setting the height
Most sternum straps slide up or down a short track sewn to each shoulder strap. The right height sits roughly one to two inches below the collarbone, across the upper chest rather than near the throat or down near the ribs. Too high, it can rub the neck or interfere with head turns; too low, it does less work keeping the shoulder straps aligned.
Setting the tension
Buckle the strap and pull it just tight enough that the shoulder straps stop drifting outward with each stride, but not so tight that it compresses the chest. A sternum strap cinched too far adds pressure across the chest and can feel uncomfortable on long climbs, without helping carry any weight.
Where it fits in the adjustment order
The sternum strap is adjusted after the hipbelt, shoulder straps, and load-lifter straps, and before hipbelt stabilizer straps. It plays no role in transferring pack weight — that's the hipbelt's job — so setting it earlier in the sequence, before the load-bearing straps, doesn't help and can mask problems with the fit underneath it.
Quick troubleshooting
Chest feels restricted on climbs: loosen the strap by an inch or two; tension, not height, is usually the cause.
Shoulder straps still slide outward: tighten slightly, or check that the strap sits at chest height rather than too low.
Rubbing near the throat: slide the strap down its track to a lower position on the chest.
Height: what the sources say
Published guidance clusters just below the collarbone. Big Agnes says the sternum strap should sit below the collarbone and lie flat with moderate tension,1 while Alpkit gives about an inch below the collarbone.2 The page's one-to-two-inch range extends a little beyond what the verified sources state, so an inch is the safest starting point.
Some guides say a low strap presses on the diaphragm during heavy breathing, a claim that is not in the source library. It is plausible, but treat it as a comfort observation rather than an established effect. What is well supported is the sequence: Deuter says the sternum strap height is set after the back length is correct.3
Tension and strap pressure
The sternum strap is a positioning strap, not a load-bearing one, so extra tension adds pressure without adding support. A PLoS One study found static strap force is a significant predictor of discomfort during load carriage.4 That supports this page's advice to keep the strap snug rather than cinched.
If the shoulder straps keep sliding outward even with the chest strap reasonably tight, the harness may not suit your shoulders. ULA, for example, offers J-shaped straps for flat or square shoulders and S-shaped straps for standard or sloping shoulders.5 Deuter's women's SL packs use narrower S-shaped shoulder straps for a similar reason.6
When discomfort isn't about the strap
Most chest tightness from a sternum strap goes away as soon as it is loosened, which is the quick check the page recommends. If it does not, the cause may be something else. Chest pain or trouble breathing that persists after loosening the strap or taking the pack off is a reason to stop and get medical help.
Numbness or tingling in the arms is a related warning sign. Rucksack palsy, a nerve problem linked to shoulder-strap pressure, is listed among common injuries from prolonged load carriage,7 and a 2021 review notes load-carriage injuries include neurological problems such as paresthesias, or pins and needles.8 Symptoms like these call for a doctor's advice, not just a strap adjustment.
