This chapter discusses artificial or simulated altitude methods, which emerged to make altitude training more accessible and cost-effective compared to conventional mountain camps. Pioneered by Scandinavian scientists in the 1990s these techniques aim to mimic the performance-enhancing effects of natural altitude in a controlled, safe, and legal way. To do this, we can use either normobaric hypoxia (reducing oxygen concentration while maintaining sea-level barometric pressure), or hypobaric hypoxia (reducing the barometric pressure in a chamber thereby reducing the oxygen available). While hypobaric hypoxia more closely mirrors natural conditions and is theorized to offer added benefits, studies suggest that for performance enhancement, the overall outcomes of normobaric and hypobaric LHTL protocols are similar, provided the total hypoxic dose is sufficient.