1. An active exoskeletal spinal orthosis, comprising: an upper member comprising one or more upper body portions that together can extend circumferentially around a body part of a user; a lower member comprising one or more lower body portions that together can extend circumferentially around the user at a location below the upper member, wherein the upper and lower members can be attached to the user at two spaced locations that are separated by at least a portion of the user's spine; a plurality of actuators, each actuator having a first end and a second end; wherein the first end of each actuator is coupled to the lower member and the second end of each actuator is coupled to the upper member such that the actuators extend between the lower member and the upper member; at least one sensor measuring one or more physical parameters indicative of a bending moment caused by gravity, a bending moment caused by muscle force, or a bending moment caused by gravity and muscle force; and a controller that receives input from the sensor(s) and activates one or more of the actuators to apply a corrective moment, a distraction force, or both to the user's spine that at least partially counteracts the bending moment applied by the user.