An apparatus for resistance-based fitness training comprising: a joint mechanism; a joint casing enclosing the joint mechanism; a locking device secured within the joint casing that selectively engages the joint mechanism in a locked mode and in an unlocked mode; an actuator partially protruding from the joint casing mechanically connected to the locking device; wherein the joint mechanism comprises at least one joint coupling connector, and wherein each of the at least one joint coupling connector is capable of mechanically engaging with a device external to the joint casing; and wherein when the joint mechanism is in the unlocked mode, each of the at least one joint coupling connector mechanically is capable of allowing each of the devices external to the joint casing that is mechanically engageable with each of the at least one joint coupling connector to rotate within three-dimensional space; and wherein when the joint mechanism is in the locked mode, each of the at least one joint coupling connector is capable of preventing each of the devices external to the joint casing that is mechanically engageable with each of the at least one joint coupling connector from substantially deviating from the position in three-dimensional space that each of the devices external to the joint casing that is mechanically engageable with each of the at least one joint coupling connector occupied just prior to the engagement of the joint mechanism in the locked mode; wherein the at least one joint coupling connector comprise a first joint coupling connector and a second joint coupling connector and wherein the first joint coupling connector and the second joint coupling connector are in substantially orthogonal positions within the joint mechanism; thereby the rotation of the device external to joint casing that is mechanically engageable with the first joint coupling connector being not co-planar with the rotation of the device external to the joint casing that is mechanically engageable with the second joint coupling connector; characterised in that the actuator comprises a locking actuator and an unlocking actuator, and wherein the locking actuator protrudes from the joint casing when the joint mechanism is in the locked mode and wherein the unlocking actuator protrudes from the joint casing when the joint mechanism is in the unlocked mode. a joint mechanism; a joint casing enclosing the joint mechanism; a locking device secured within the joint casing that selectively engages the joint mechanism in a locked mode and in an unlocked mode; an actuator partially protruding from the joint casing mechanically connected to the locking device; wherein the joint mechanism comprises at least one joint coupling connector, and wherein each of the at least one joint coupling connector is capable of mechanically engaging with a device external to the joint casing; and wherein when the joint mechanism is in the unlocked mode, each of the at least one joint coupling connector mechanically is capable of allowing each of the devices external to the joint casing that is mechanically engageable with each of the at least one joint coupling connector to rotate within three-dimensional space; and wherein when the joint mechanism is in the locked mode, each of the at least one joint coupling connector is capable of preventing each of the devices external to the joint casing that is mechanically engageable with each of the at least one joint coupling connector from substantially deviating from the position in three-dimensional space that each of the devices external to the joint casing that is mechanically engageable with each of the at least one joint coupling connector occupied just prior to the engagement of the joint mechanism in the locked mode; wherein the at least one joint coupling connector comprise a first joint coupling connector and a second joint coupling connector and wherein the first joint coupling connector and the second joint coupling connector are in substantially orthogonal positions within the joint mechanism; thereby the rotation of the device external to joint casing that is mechanically engageable with the first joint coupling connector being not co-planar with the rotation of the device external to the joint casing that is mechanically engageable with the second joint coupling connector; characterised in that the actuator comprises a locking actuator and an unlocking actuator, and wherein the locking actuator protrudes from the joint casing when the joint mechanism is in the locked mode and wherein the unlocking actuator protrudes from the joint casing when the joint mechanism is in the unlocked mode.