i suppose sand could help. its depends on what part you run. the dry part is defenitely hardest but the closer part near the water is usually more firm. but if you click the training button on the left then SPARQ it has a section on explosive that looks pretty good. however, this sounds like more of a stamina issue since you said, 'they eventually catch up to me'. theres a SPARQ section on that as well. best of luck mate