Yes. In 2008 I had problems with angina and had to be stented, they put 4 in. On the bike climbing, sprinting and pushing very hard triggered the angina, off the bike sprinting for the bus and anything else that raised the heart rate triggered the angina. I was very fit and had been a club cyclist for very many years. In a way I consider myself as lucky, my heart could have just handed its notice in with immediate effect, the blocked arteries were putting it under stress. There are heart conditions that are very difficult to detect and as you age heart conditions can develop, genetics or lifestyle, so anyone who is fit active and pushes themselves physically has some risk.