Why do sports stars collapse in action?

Story highlightsSoccer player's tragic collapse sparks debate about heart problems in sporting arenaEnglish doctor says that top-level competition can unmask underlying health conditionsCardiologist in U.S. says that screening cannot always discover these problemsThey both call for more heart testing for top sports playersThe on-pitch collapse of an English Premier League soccer player at the weekend raises questions about how such highly-trained athletes can be struck down in such a manner.

Professional sports players are generally in prime physical condition, especially with today's advanced physiological, nutritional and medical knowledge.

However, Fabrice Muamba is the late