Can running too far be bad for your health?

Ever since I announced in my previous column that I am training for a half marathon, friends keep asking me whether a full marathon is up next. My answer is always the same – no way. While running 21 kilometres seems a manageable challenge, running 42 just feels self-punitive. But all of this inquiring has me wondering whether there is an upside – or downside – to longer races.

Research in this area is scant, but a few studies do indicate declining returns, and even some evidence of harm.…