What the evidence actually answers
A systematic review of running economy found benefits for high-load, plyometric and combined methods under different conditions. Programmes lasted 6–24 weeks and used one to four sessions weekly. These ranges describe the studies; they are not instructions to copy the largest dose.
An earlier review included only five trials and 93 highly trained runners. It supports investigating strength alongside endurance work, but does not establish injury prevention or a universal beginner programme.
For a practical week, identify the key run first, place a familiar strength session where it can be recovered from, and review the next run before adding another session. Use the running and strength schedule guide for the scheduling decision.