My client is in great shape and keeps up her runs with a local running club. She works with me twice each week to supplement her running. I’m not able to do vertical jumping as per her chiropractor (was only doing 1-2 sets 1x per week) and single-leg work seems to aggravate an old ankle/calf injury. Basically I can’t do any of the regular things I would do with my runners. Any suggestions?
While you have already received many good suggestions, before providing any specific input, it would be beneficial to know more about the clients running history and how long she has to prepare before running the half marathon. If she is new to running you need to build her “base” mileage gradually. An increase of 10% per week is usually safe progression. If this is her first half marathon she should be running just to finish and not be targeting a specific time goal.
With that being said, plyometrics or any type of interval training is really not necessary. This is especially true for this client since you indicated she had some problems with a previous ankle and calf injury. As others mentioned I would definitely work on strengthening her core. I would also add some regular and single leg squats, lunges, and some hip flexor stretches. The key for this client is to get her to the starting line healthy. This can be done with moderate and sensible training progression, and by improving her stability.