The amount of exercise and fitness level of sports athletes can be quantitatively evaluated through the measurement of health and sports information, thereby ensuring effective fitness effects. The development of blockchain and Internet of Things technology provides a new perspective and technical means for fitness management technology. In view of the current problems in the field of sports fitness, this paper designs and implements a dynamic management technology for sports fitness based on the concept of Internet of Things and blockchain. First, based on an in-depth analysis of the current status of theoretical research and application of the Internet of Health at home and abroad, the theories and methods of sports information and health information collection are studied. A temperature sensor and an acceleration sensor are used to collect human body temperature and exercise steps, respectively, and then estimate human health and exercise conditions. Second, solve the privacy problem in the collection and transmission of the Internet of Things by adding blockchain technology. Finally, the machine learning method is used to clean and manage the information and data to realize the real-time detection and management of the athlete's fitness status. The actual case test shows that the functions and technical performance indicators of the dynamic fitness management technology can meet the needs of users in indoor and outdoor fitness management, and promote the development of the sports industry and provide a scientific reference.