As a result of doing the same effective training program, there were no significant differences between the groups in total training volume or any of the other categories. (onnit.com)
Once it takes a reasonable amount of effort, it's time to add some strength and power training (15 - 20 % of total training volume) such as weights, sprints, intervals, etc.. (philmaffetone.com)
Moderating total training volume is tricky with on - season athletes. (blog.trainheroic.com)