A portable exercise device for use in resistance training programs is provided, which can comprise: a hollow structure; multiple resistance bands, each shorter than the hollow structure; multiple anchor members for securing the resistance bands to the hollow structure; multiple attachable and detachable handles; wherein one end of each resistance band is coupled to an anchor; wherein an opposing end of each resistance band is operably configured for attachment to a handle; such that each resistance band is contained completely within the hollow structure during rest and is capable of extending outside the hollow structure during use when attached to a handle. Such devices can be used by attaching a handle to a resistance band at each end of the hollow bar, gripping the bar with hands, placing feet in the handles, and moving the bar away from the feet to create resistance in the bands thereby exercising the user's body. Such devices can also be used by attaching a handle to the resistance band at each end of the hollow bar, whereby the handle is three-sided and each side serves a different adapted function; for example, one side may be configured for gripping by a user's hand, one side may be configured for engaging by the user's foot, and one side may be configured to anchor to an anchoring structure.