What is the definition of retention as it pertains to helmets?

Retention, in the context of helmets, specifically refers to the ability of the chin strap to remain securely fastened while providing protection during an activity. A helmet with good retention ensures that it stays in place during use, even if the rider experiences impacts or sudden movements. This is critical for safety because if the helmet shifts or detaches, it reduces the level of head protection and increases the risk of injury.

The other options deal with different aspects of helmets but do not define retention. The fit of the helmet is important for comfort and overall safety but is separate from the concept of retention. The style of the helmet pertains to its appearance and design, rather than its functional attributes related to safety. Lastly, the materials used in a helmet's construction affect its strength and durability, but these factors also do not directly relate to how well the helmet is retained on the head. The correct answer emphasizes the functional aspect of the chin strap as a key component of helmet safety and effectiveness.