B.C. news was recently covering the story of a woman who had medical travel insurance for her trip to the U.S.A. She was seriously injured while skydiving. Insurance did not cover the half-million dollar cost of treatment because the policy did not cover "extreme" sports. Her family & friends are fundraising now to help pay the US medical bills.
Be sure to read the fine-print.
One policy I purchased covered "sports" but not "competitive" or "professional" sports. Since I was in Oregon for a competitive event, I simply ensured I was extra cautious while competing!