Tennis elbow is one of the more common repetitive stress injuries in kendo. This video describes some of the things I tried to treat it.

The New York Times article on the clinical trial for tennis elbow using the Flexbar: http://nyti.ms/1BbTg8n

Amazon link to the Flexbar: http://amzn.to/1GmsyZr

Disclaimer: I'm not a doctor and this shouldn't be construed as medical advice. This is information that comes from my own experience with kendo and with tennis elbow.