Objective of the study was to substantiate the expediency of use of load testing toolkit with application of a gas analyzer for the management of the athletic training process. Methods and structure of the study. Sampled for the study were 11 triathletes (mean age - 33.4±2.7 years, body length - 181.3±5.2 cm, body weight - 81.8±10.2 kg). Load testing with the use of the cycle ergometer Schiller Ergosana 911 (Schiller AG, Switzerland) and portable metabolic analyzer FitMate Pro (COSMOED, Italy) was conducted according to the maximal protocol ("to failure") with a constantly increasing load - RAMP protocol developed upon the international recommendations. Study results and conclusions. The first load testing revealed a low strength index and low oxidizing potential of the leg muscles, insufficient pulmonary ventilation and maximum oxygen consumption, as well as their desired values for triathletes. We substantiated recommendations for planning the training process, namely: increase of the share of physical load directed on hypertrophy of the muscles, strength endurance, increase of oxidizing capacity of the transitional and fast muscle fibers involved in the competitive activity in triathlon. The comparative analysis of the load test rates in 4 months revealed statistically significant growth of all fitness indices and, as a result, of such integral indicator as maximum oxygen consumption. Consequently, the stage control of load testing of the athletes made it possible to determine the required orientation of training interventions, thus increasing the reliability of management and ultimate efficiency of the training process.