there are many specialist sports insurance companies out there and their offerings can range from simple travel insurance cover for non-dangerous sports like running, through to extreme sports cover
we ski, bike (road and off road), do triathlon, climb so get a high level of cover to cover all eventualities, and for us it's easier to have one annual policy that covers all eventualities. we currently use dogtag.co.uk but have in the past used snowcard.co.uk - probably the best 2 of their type. I had to make a claim with Snowcard after a skiing accident involving helicopter rescue (that ain't cheap!!) - they sorted everything with one phone call. brilliant service but it's not cheap.
stick "sports travel insurance" into Google and you'll find loads of companies offering sports cover - but make sure you read the small print to make sure it covers what you want, and if in doubt always call. and don't forget that if you have any medical conditions, you declare these in advance or you may find that a claim could get refused if you haven't done so.