One of the main problems of introducing corporate Web 2.0 systems in organizations is the problem of low motivation of the employees to adopt and use these systems, caused by the fact that introduction of corporate Web 2.0 is usually an initiative not of the employees, but of the senior management of the company. However, one of the most crucial conditions of success in introducing such systems is the interactivity of the employees' usage of the systems, which can potentially be stimulated by applying the gamification practices. Among different areas of gamification practices, we think that the fitness gamification area has interesting experience for motivating the employees to adopt and use the corporate Web 2.0 systems, as most prominent fitness gamification projects are based on Web 2.0 technologies themselves. On the basis of fitness gamification projects experience we suggest and analyze a set of metrics that can be used for assessing and rewarding the employees' individual and collective activity in sharing and creating knowledge via the corporate Web 2.0 systems. The analysis results in recommendations to use such metrics as amount of specific types of knowledge shared or created via the corporate Web 2.0 system, uniqueness of the knowledge shared via the corporate Web 2.0 system and uniqueness of the knowledge created via the corporate Web 2.0 system.