Which succinct definition best describes 'flexibility' as a component of physical fitness?

The ability of a joint to move through its full range of motion without pain or significant restriction.

The percentage of body mass composed of contractile tissue such as muscle, typically measured with body composition analysis rather than joint testing.

The speed at which a limb can be moved through a joint's range of motion under maximal power output, as measured by isokinetic dynamometry at extremely high angular velocities.

The amount of force a muscle can exert in a single maximal contraction, typically assessed by 1RM testing at the joint being measured.