A lower back assistance apparatus (10, 50) comprising: an upper body mounting section for mounting to an upper body of a user and capable of following movement of a user tilting forward; a support section attached to the upper body mounting section, extending towards a user trunk front side or trunk rear side, and supporting the user at the trunk front side or trunk rear side; a lower limb mounting section for mounting to a lower limb of the user at least at a front side of the lower limb; a coupling section, a portion at a first end of the coupling section being coupled to the lower limb mounting section, a portion at the second end of the coupling section being coupled to the upper body mounting section by a joint section so as to enable relative movement of the coupling section with respect to the upper body mounting section so as to permit the following movement of the upper body mounting section, and the coupling section being capable of maintaining a non-bent profile during the relative movement; an actuator that is configured to cause, in an actuated state, a force to act on the upper body mounting section countering the forward tilting of the user, by generating a tension force on a wire extending out from a first end of the actuator; and a clutch mechanism (60, 100) is provided at the joint section, the clutch mechanism (60, 100) comprising a rotation body with a peripheral section around which the wire is wrapped, and the clutch mechanism (60, 100) is configured so as to fix the rotation body to the upper body mounting section or to the coupling section when the actuator is actuated such that tension force of the wire acts on the upper body mounting section or on the coupling section from the time of initial actuation of the actuator; characterised in that: the actuator is a pneumatic actuator that contracts when internally supplied with air, and the clutch mechanism (60, 100) is a pneumatic clutch mechanism (60, 100) which is supplied with air at the same time that the pneumatic actuator is supplied with air and is adapted to fix the rotation body to the upper body mounting section or to the coupling section with said air supply. an upper body mounting section for mounting to an upper body of a user and capable of following movement of a user tilting forward; a support section attached to the upper body mounting section, extending towards a user trunk front side or trunk rear side, and supporting the user at the trunk front side or trunk rear side; a lower limb mounting section for mounting to a lower limb of the user at least at a front side of the lower limb; a coupling section, a portion at a first end of the coupling section being coupled to the lower limb mounting section, a portion at the second end of the coupling section being coupled to the upper body mounting section by a joint section so as to enable relative movement of the coupling section with respect to the upper body mounting section so as to permit the following movement of the upper body mounting section, and the coupling section being capable of maintaining a non-bent profile during the relative movement; an actuator that is configured to cause, in an actuated state, a force to act on the upper body mounting section countering the forward tilting of the user, by generating a tension force on a wire extending out from a first end of the actuator; and a clutch mechanism (60, 100) is provided at the joint section, the clutch mechanism (60, 100) comprising a rotation body with a peripheral section around which the wire is wrapped, and the clutch mechanism (60, 100) is configured so as to fix the rotation body to the upper body mounting section or to the coupling section when the actuator is actuated such that tension force of the wire acts on the upper body mounting section or on the coupling section from the time of initial actuation of the actuator; characterised in that: the actuator is a pneumatic actuator that contracts when internally supplied with air, and the clutch mechanism (60, 100) is a pneumatic clutch mechanism (60, 100) which is supplied with air at the same time that the pneumatic actuator is supplied with air and is adapted to fix the rotation body to the upper body mounting section or to the coupling section with said air supply.