This means that you run for sometime, and then stop to lift some weights followed by run other. They build muscle and power in the hamstrings and glutes and also hit the less back quite nicely. That being said an air hoist can be provided in many applications that want spark resistance. https://milet.xn----7sbbrpcrglx8eea9e.xn--p1ai/triciaswader96/6247lifting-chain/wiki/Tight-Hips-And-The-Domino-Affect-Training