Hi, I have gone through the medical history of your wife, and here s my advice. The stabbing pain in the right thigh and armpit could be related to post-workout soreness. However, at her age, we should exclude possible cardiovascular event after cardio-tennis exercises. Furthermore, shivering after having a shower after workout is also related to possible reaction to getting over-exercised. I advise to give her paracetamol for the pain, let her rest, and give her plenty of fluids. Magnesium supplement will help ease muscle soreness and pain. If still in pain, should consult with her caring doctor immediately to rule out any possible cardio-vascular event. I think she should rest for a few more days without working out on cardio-tennis clinic. Report this to her caring doctor there. Hope I have answered your query. Let me know if I can assist you further. Regards, Dr. Albana Sejdini