Why can heavier body armour reduce a soldier's mobility and stamina?

Heavier body armour systems, such as the Interceptor Body Armor (IBA) or the Osprey Assault kit, significantly increase the physical burden placed on an infantryman. A complete set of enhanced body armour, including all inserts and add-on components, can weigh upwards of 33 pounds (15 kg).1

This added weight directly impacts a soldier in the following ways:

• Decreased Mobility: The bulk and weight of advanced protective systems can restrict a soldier's range of movement, particularly in tactical situations like prone firing positions.1
• Reduced Stamina: Carrying such a substantial load—especially when operating on foot in extreme heat—demands more physical energy, leading to increased fatigue and decreased comfort.1

While these systems are essential for protecting vital organs against shell fragments and high-velocity projectiles, the trade-off is a considerable physical burden that can hinder a soldier's ability to remain agile when fighting mobile, lightly armed adversaries.1