Objective: This study aims to analyze the gait characteristics of firefighters during stair climbing under weight-bearing conditions to assess their impact on energy consumption. Firefighters frequently engage in high-intensity tasks, such as carrying heavy equipment upstairs in high-rise buildings, which can significantly affect their physical performance and increase fatigue. Understanding the intricate relationship between gait parameters and energy consumption in these strenuous conditions is crucial for optimizing training efficiency and improving operational efficiency in fire rescue actions. This study not only investigates gait changes owing to loads but also seeks to establish a predictive model to help in training and operational planning. Methods: The study involved 24 healthy male subjects for two experiments. Experiment (A) performed stair climbing without additional weight, while Experiment (B) carried approximately 26.9 kg of firefighting gear, including protective clothing, a breathing apparatus, and a fire hose, simulating the typical loads that firefighters bear during emergencies. A 3-D gait analysis system captured motion data, including step frequency, step length, stride length, and overall energy consumption. The system also measured single- and double-leg support phases, cycle time, and other gait characteristics relevant to assessing performance under loads. Statistical analyses compared gait differences between weight-bearing and non-weight-bearing conditions, while correlation analyses identified relationships among energy consumption and specific gait parameters, highlighting factors significantly influencing fatigue. Results: The results revealed that weight-bearing conditions led to significant changes in gait characteristics. Specifically, step frequency, step length, and stride length significantly reduced, indicating reduced movement efficiency when carrying heavy loads. Conversely, energy consumption, single-leg support time, double-leg support time, and cycle duration increased markedly, highlighting the added physical demands placed on firefighters. Correlation analysis indicated strong associations between energy consumption and several key gait parameters, including double-leg support time, cycle duration, speed, step length, and stride length. These findings suggest that specific gait adaptations occur in response to increased loads, which in turn affect overall energy consumption. To quantify these relationships, a support vector machine (SVM) model was developed to predict energy consumption using these gait parameters, achieving a high accuracy with R² of 0.858 36, thus confirming the model reliability. This result suggests that the SVM model is a reliable tool for estimating the energy consumption associated with weight-bearing stair climbing in firefighters. Conclusions: The study highlights the considerable impact of weight-bearing stair climbing on firefighters' gait characteristics and energy consumption. Prolonged exposure to such strenuous tasks can lead to significant physical fatigue, increasing injury risks. The predictive SVM model developed in this study provides valuable insights into how specific gait parameters contribute to overall energy consumption, offering a robust foundation for optimizing firefighter training programs. By improving gait mechanics and reducing energy consumption during high-intensity tasks, this research enhances firefighter safety and performance in emergencies. Future research could explore the long-term effects of repeated weight-bearing activities on firefighter health and develop strategies to mitigate fatigue and injury risks, leading to improved training protocols that emphasize strength and endurance, ultimately benefiting firefighter well-being and operational readiness.