A modular endurance conditioning tank system for multi-activity strength and endurance training, over a plurality of surfaces and terrain, that reduces the risk of athlete injury. The modular endurance conditioning tank assembly is useful for manually-maneuvering a steel chassis/frame assembly while applying varying amounts of weights and resistance for athletic strength and endurance conditioning. The modular endurance conditioning tank assembly may include a steel chassis/frame assembly, at least one wheeled continuous-track system, at least one steel shaft, a T-shaped handle, at least one hand-hold receiver, a barbell-weight plate receptacle, and a complementary strap, harness, and alternatively user-worn apparel. The steel chassis/frame assembly may have at least one wheeled continuous-track system and the at least one wheeled continuous-track system may further have a left-track assembly, a right-track assembly, and a double wheel disc brake system. Further, the double wheel disc brake system may include a resistance adjusting knob.