physical training systems that may promote effective technique and strength training for various sports , as well as general strength and fitness training . apparatus may require a user to push and lift in a coordinated manner to effectively overcome inertia and rolling resistance . the training apparatus may include a cylindrical core portion and compliant outer portion located on an outer surface of the core portion . in use , the training apparatus may rotate around a center axis of the core portion when a sufficient force , exceeding a resistance level , is received by the training apparatus . the resistance level may be a result of a configurable amount of ballast contained within the apparatus .