Despite the growing participation of women in sport and the notable sex differences in anatomy, physiology and endocrinology, sport and exercise science research remains male-dominated. Consequently, women are often prescribed training guidelines based on male data, which may limit their performance. Developing sex-specific strategies is therefore essential. Recently, repeated sprint training in extreme environmental conditions, such as hypoxia or heat, has gained attention, as it is suggested to enhance repeated sprint ability (RSA) under usual competition conditions (i.e., normoxic and temperate conditions). In this thesis, we show that seven weeks of repeated sprint training in either hypoxia or heat, performed twice per week, improves RSA in both males and females. This time efficient approach can be integrated into a regular training routing, and it can be particularly beneficial for athletes practicing intermittent sports, such as football, tennis or boxing, in which RSA is crucial.