TrainingPeaks is an excellent online platform, both for coaches and athletes. I use TrainingPeaks myself as an athlete and have used the coach app since 2013. TrainingPeaks already has millions of users plus used by some of the worlds leading sporting bodies including British Athletics and British Triathlon. TrainingPeaks offers some brilliant features like allowing the athlete to upload and view their workout data from a lot of different devices and adding various metrics such as weight and sleep to get the most out the plan. You can access TrainingPeaks via your mobile device or tablet as well as via a desktop browser so it’s really easy to access training on-the-go!