I recently started playing tennis again following a layoff of about two months. On resumption yesterday I had no physical side effects apart from a stomach strain on my left side ( I am right handed) which I attribute to serving following not having served for two months. I only experience pain when I serve – there is no residual pain. I would appreciate someone answering the following queries from anyone who has had a similar experience: How long is the pain/strain likely to last. Is there any treatment I can administer. Is it ok to hit groundies with the strain if there is no pain. Thanks in advance.