Alpinestars Bionic Plasma Youth Knee Protector - Black

Alpinestars Bionic Plasma Youth Knee Protector - Black

Alpinestars Bionic Plasma Youth knee and shin guards carry CE certification to EN 1621-1 Level 1, built around Nucleon Plasma — a padding compound Alpinestars developed specifically for cycling protection (MTB/BMX). The material hardens on impact to absorb the hit, and stays soft and flexible through normal movement. A 3D M-profile shell channels airflow up to 50% better than comparable guards (per Alpinestars testing), and a multi-directional ergonomic fit follows the shape of a kid's knee. The pair covers the knee and upper shin, built for cycling, BMX, and enduro riding, not casual use without real fall risk.

Nucleon Plasma — hardens on impact, stays flexible otherwise

Nucleon Plasma is a viscoelastic compound Alpinestars built on a base similar to d3o and developed further specifically for cycling protection (MTB/BMX). On impact, the material hardens and absorbs the hit; during normal movement it stays elastic and comfortable — protective performance exceeds standard requirements by tens of percent per Alpinestars testing. The padding is multi-layer: 3D engineering gives the protective element a 3D M-profile that maximizes airflow both vertically and horizontally (away from the body and around it) — up to 50% better than comparable guards according to testing. The inner layer is a high-durability microfiber that adds comfort, minimizes friction, and resists tearing. More than half of the material falls into the Bio Raw category.

What does EN 1621-1 Level 1 certification mean?

EN 1621-1 measures how much impact force a guard transmits through to the body. Level 1 allows a mean residual force of up to 35 kN, the stricter Level 2 caps it at 20 kN — Bionic Plasma Youth is certified to Level 1, the standard tier for knee guards in cycling. The test runs against an instrumented anvil, not living tissue.

Ergonomic fit and airflow — mesh, side padding, silicone hems

The multi-directional cut follows a kid's knee anatomy and lets the joint bend through its full range without the sleeve riding up or digging into the back of the knee. The front 3D mesh panel and abrasion-resistant fabric hold shape through longer rides, while stretch mesh at the rear of the calf fits different leg sizes. Side padding extends coverage, and silicone hem strips at the top keep the guard in place on impact.

Sizes S/M, L/XL and XXL — how to choose

Bionic Plasma Youth comes in three sizes — S/M, L/XL, and XXL — sized by thigh circumference and leg length, not by age alone. See the size chart image for exact figures: S/M fits a 27–31 cm thigh, L/XL fits 31–35 cm, XXL fits 35–39 cm. On a borderline measurement, size up so the guard still fits after the leg grows through the season.

Full technical specifications are available in the Specifications tab on the product page.

Frequently Asked Questions

What's the difference between Level 1 and Level 2 under EN 1621-1?

Level 1 allows a mean residual force of up to 35 kN, Level 2 caps it at 20 kN — the lower the number, the less impact force reaches the body. Bionic Plasma Youth is certified to Level 1, the standard tier for kids' knee guards in cycling. Level 2 guards tend to run stiffer and heavier, more common on motocross or DH protection.

Does it protect the shin too, or just the knee?

The guard covers the knee and extends onto the upper shin, covering ground a knee-only cap misses. Full coverage details are in the Specifications tab.

How does the Nucleon Plasma material work on impact?

The material stays soft and flexible during normal movement, then hardens within a fraction of a second on impact to absorb the hit. It returns to its flexible state once the impact passes.

How do I choose between S/M, L/XL, and XXL?

By thigh circumference: S/M 27–31 cm, L/XL 31–35 cm, XXL 35–39 cm (exact figures in the size chart image on the product page). On a borderline measurement, size up.