Research on sport performance is heavily related to basic biology, physiology, psychology, medicine and sport science. Modern sport is introducing complex multi-level research in order to understand performance differences as function of genetics, diet and training scheme. Training scheme design is known to have a great impact on performance. Altitude training (AT) has been a matter of extensive research for half a century and despite some skeptical views it still plays an important role in the preparation of athletes in many countries. The research team has previously completed an international multidisciplinary and collaborative research project (ALTITUDE Project) to examine the impact of different current AT strategies on performance, technique, and health status of 65 elite swimmers from eight countries. This line of research is continuation of that developed by the INEFC-UB Hypobaric Unit since 1991 using experimental models of exposure to intermittent hypoxia. On a first published analysis, disruptive results were obtained, as only one group living and training both at altitude and at sea level (Hi-HiLo) improved performance more than sea level controls and, more importantly, no relationship was found between increased performance and VO2max, anaerobic capacity or swimming economy. These results leave room for unidentified muscle factors. In a second, related project (TEC2014-60337-R project), the research group has analyzed linear (time and frequency domains) HRV indices in athletes participating in endurance running races. We also developed tools for the identification of almost one fourth of all protein-coding genes with differential expression in a group of 16 runners participating in an 82-km ultra-marathon trail competition, showing clear differences between biological pathways and transcriptional regulators (TRs), identified through independent component analysis factorization, and in HRV throughout the race and in contrast to the athlete training. The project aims for the understanding of the differences in performance between sea level and moderate altitude training. This understanding must cover two phases: first a deep characterization of the available data and biological samples at different levels, including metabolomic profiling, study of noncoding transcriptional regulators, assessment of the autonomous nervous system activation and performance data; secondly, an integrated analysis of the different domains linking physiological data with metabolomic and genetic profiling, biological interpretation of these interactions and cross-validated prediction models of performance and health related indexes. ALPE project will therefore extend the results from both projects by understanding the optimal physiological, cardiovascular and metabolomics conditions of altitude training and competition in a quantitative way, as well as correlate them with risk or negative impact in terms of health or performance for the athlete himself. The project will deepen into the integration of metabolomics with phenotypic data by the analysis of complex and heterogeneous data in a multi-level scheme. UPC previous experience in transcriptomics and HRV analysis in sport, INEFC large expertise in sport sciences, and Hospital de la Santa Creu i Sant Pau (HSP) in genomics grant the feasibility of the project.