Alpinestars A-5 S Youth Chest Protector – CE chest and back protector for MTB, BMX and motocross
A youth chest and back protector needs to cover the two spots that take the worst hits in a crash – the chest and the spine – at CE Level 2 front and back, with Level 1 on the shoulders and elbows. The Alpinestars A-5 S Youth builds on Polyhedron Hybrid Technology with a floating chest, back and rib guard, so the protection moves with the body instead of fighting it. Vents cover over 17% of the surface, and riders consistently report above-average airflow even after a long stint under a jersey. It's built for more advanced riding — MTB enduro, slopestyle, freeride, jibbing — plus BMX and motocross, disciplines where the odds of a hit to the chest or back rise with the terrain.
Key features: Alpinestars A-5 S Youth
- CE Level 2 chest and back (EN 1621-3:2018 / EN 1621-2:2014): the highest commonly available torso protection, backed by Level 1 on the shoulders and elbows (EN 1621-1:2012).
- Floating Polyhedron Hybrid Technology: the chest, back and rib guards aren't rigidly fixed, so they follow the body through a forward lean or a deep breath.
- 17% of the surface is ventilation apertures: riders report above-average airflow even on long rides under a jersey.
- Comfort padding foam on the rib guards: a softer seat against the ribs without losing impact stiffness.
- Detachable chest and back panels: come off separately for washing, so you don't have to wash the whole protector at once.
- YNS neck brace compatible: via a removable puck panel on the back protector.
- V-straps on the back protector: adjustable V-shaped straps adapt the fit to a young rider's build.
- Race-proven base layer fabric: breathable, stretchable material keeps the protector in place through movement.
Multi-zone CE protection for enduro, freeride and motocross
The EN 1621 standard measures how much impact force a protector lets through to the body — the lower the number, the better the protection. On the back (EN 1621-2:2014), Level 2 caps that at 9 kN, half of Level 1's 18 kN — and that's the tier the A-5 S Youth runs both on the back and the chest (EN 1621-3:2018). The shoulders and elbows (EN 1621-1:2012) stay at Level 1, capped at 35 kN, the usual trade-off between protection and the arm mobility that enduro, freeride and a motocross landing all demand. In practice, that means a lower chance of a broken rib or a bruised spine in a crash at the speeds enduro and bike park trails are built around.
Floating Polyhedron Hybrid Technology
A conventional protector stitches its padding straight onto the frame — lean forward or swing an arm hard, and it shifts and digs into the body. Polyhedron Hybrid Technology treats the chest, back and rib guards as floating segments hung on a flexible frame, so each panel pivots on its own as the chest moves — climbing out of the saddle, leaning into a corner, or landing a jump. The result doesn't sit fixed in one spot like a rigid body armour shell; it tracks the shoulders and torso even through hard standing efforts on the pedals.
17% ventilation and panels you can remove for washing
Ventilation apertures run through the hybrid layers across 17% of the surface, keeping air moving under a jersey on a long climb or in hot trail conditions. The chest and back panels also unclip separately, so only the sweaty part needs a wash instead of the whole protector. Paired with those removable panels, it holds up to ride after ride without lingering odor or soggy foam.
YNS neck brace compatibility
A removable puck panel on the back protector clears space for the puck of an Alpinestars YNS (Youth Neck Support) brace, so the brace seats directly on the protector instead of riding over it and lifting with head movement. Without a brace, the panel just stays in place and the protector works on its own. It's the same setup motocross gear typically uses, where the neck brace and torso protector work as one linked system rather than two separate pieces.
Built for more advanced MTB, BMX and motocross riding
The A-5 S Youth targets riders already doing more than an easy afternoon ride — enduro and slopestyle on a bike, jibbing in the bike park, BMX freestyle or motocross. The odds of a chest or back impact climb with the terrain and jump height in those disciplines, so dual Level 2 CE certification front and back makes sense for younger riders too, not just adult racers.
Full technical parameters are available in the Specification tab, and the size chart is in the product photo gallery.
Frequently asked questions (FAQ)
What's the difference between CE Level 1 and Level 2?
Level 2 lets noticeably less impact force through to the body than Level 1 — on the back standard EN 1621-2, that's 9 kN versus 18 kN. The A-5 S Youth runs Level 2 on the chest and back, and Level 1 on the shoulders and elbows, where keeping arm mobility matters more.
What riding is this protector suited for?
It's a more advanced protector, not a basic model for an easy ride — built for disciplines with a higher risk of a chest or back impact, like bike park and enduro MTB, BMX freestyle, or motocross.
How do I choose between S/M and L/XL?
Both are youth/junior sizes — check the exact chest measurements in the size chart in the product photo gallery. The protector should sit snug with no pressure under the arms, so it doesn't shift in a crash.
Can the A-5 S Youth be combined with a neck brace?
Yes — the removable puck panel on the back protector makes it compatible with an Alpinestars YNS (Youth Neck Support) brace; without a brace, the panel just stays in place.
How do you clean and maintain the protector?
The chest and back panels detach from the hard structure, so they can be washed separately — hand wash and air dry away from direct heat so the foam and bonded seams hold up over time.
