This paper deals with the application of Digital Human Modeling (DHM) procedures in the improvement of product ergonomics. Different methods of ergonomic assessment, their performance and several DHM programs with their characteristics are described. After that, manual ergonomic analyzes and analyzes using the Santos and CATIA programs were carried out on race car seat models. Data and parameters collected from four studies were used to make the comparison. The comparison of DHM and manual methods on the example of a formula seat aims to show their advantages and possibilities and to evaluate their usefulness in the construction process. DHM programs enable the simulation of human interaction with the product, improving or evaluating the product from the perspective of human use. The development of computer technologies in the middle of the 20th century enabled the creation of digital models of products and the environment, facilitating realistic simulations of position, movement and interaction with the environment. Manual methods, such as RULA and REBA methods for ergonomic assessments, provide validation of ergonomics in real work environments, while DHM programs enable predictive assessments of ergonomics during the construction phase. Together, these methods contribute to a complete evaluation of the ergonomic characteristics of the product, encouraging iterative improvement of constructions and optimization of ergonomics in the virtual space.