Increase your life to full capacity!
Endurance +1 items increase your life capacity by 10 percent. Four of them can be purchased in the Customize menu as you progress further through the story.
The other six are hidden throughout each mission, with the exception of File R-06. These make your venture through higher difficulties a tad easier (yes, a tad).
All of them are located in a gray item box –- use Blade Mode to open 'em!
File R-01: Coup d'Etat
At the factory, on the second floor, you'll see two fans on the wall. Slash 'em away and the vents will lead you to a catwalk behind there, which contains the item box.
File R-02: Hostile Takeover
In the room where you control the Dwarf Gekko, when you enter as Raiden, the item box is at the end of the catwalk in the northeast corner.
File R-03: Mile High
After you journey through the dark railroad tunnel, you'll arrive outside on the streets. It's behind the police barricade in the first section, in front of the balcony.
File R-04: Hostile Takeover
In the hallway prior to the freight elevator, there's a large vent on the wall you can slice open. It's behind there.
File R-05: Escape From Denver
Right at the beginning of the level, you'll find the item box in the lower left-hand corner. It's behind the World Marshal sign.
File R-07: Assassination Attempt
In the hangar, it rests on top of the stack of the crates located in the far-right corner.