The formula for marathon success?

Do online marathon prediction calculators offer too rosy a picture? Ian Williams takes a look at the formula, and offers a potentially more accurate oneIn case you had not realised, it’s marathon season – and I’m not just talking about the one on the telly – there are at least 30 listed in the Fetch Everyone race finder this month. And, while many runners are happy just to complete this challenging distance, there are plenty who are cramming their heads with calculations,