User-centered requirements engineering to manage the fuzzy front-end of open innovation in e-health: A study on support systems for seniors’ physical activity

•E-health innovation needs to consider complex real-world requirements already from the start.•The front of end innovation has been recognized as the most difficult stage to manage with the highest impact on the innovation process and its outcome.•Methods from software requirements engineering can be used manage the early stages of innovation.•Different user groups can complement each other in conveying needs and requirements from which systems can be designed.