A heavy bag for use by martial arts practitioners to practice the martial arts, the heavy bag adapted to receive a sheath about its circumferential periphery, the sheath having a plurality of vertically longitudinal sleeves or pockets for the slidable receipt of semi-rigid tubes, rods, or pellets which would therefore be disposed about the circumference of the heavy bag and when struck by a martial arts practitioner with a select anatomical body part would toughen and desensitize the particular anatomical body part. In the preferred embodiment, the sheathing would be in two parts, a lower sheathing secured about the lower portion of the heavy bag by means of hook and loop fastener means, and an upper sheathing which would depend from the four point linkage used for hanging the heavy bag, the lower portion of the upper sheathing being secured by hook and loop fasteners about the circumference of the heavy bag. Alternatively, the sheath may be permanently attached to the heavy bag and sold and used as only a body conditioner bag.