Abstract: The article discusses the effect and application value of physical fitness training program combining high-intensity training and high-volume in order to provide scientific and practical training guidance for athletes and coaches. The study shows that: (1) Short-duration high-intensity training mainly focuses on the enhancement of phosphagen supply and glycolytic metabolism, which is especially important for short-duration and high-explosive sports, and can rapidly improve the instantaneous explosive power and speed of athletes. (2) Large-volume training comparatively focuses on the enhancement of aerobic capacity, which is effective for middle- and long-distance endurance sports. (3) Both high-intensity and large-volume training have their own advantages, but the combination of them is more effective. When developing training programs, coaches must have a deep understanding of the energy supply characteristics of each sport and the individual differences of athletes, so as to provide athletes with more accurate training recommendations. Conclusion: High-intensity and high-volume training play an irreplaceable role in physical training. Coaches should make comprehensive use of high-intensity and high-volume training to maximize the training effect for different physical fitness sports and athletes' individual differences.

Key words: energy metabolism, lactate threshold model, bipolarization model, high-intensity interval training