We all know that running a [few / several] kilometres each day is good for our health, right? Well, what we didn't know, until [present / now] , is that running too much could be bad for [we / us] . New research suggests that running long distances [regularly / regulated] for many years could shorten our life [instead / rather] of extending it. The study is from the Minneapolis Heart Institute Foundation. Researcher Dr James O'Keefe said too much running can [causing / cause] plaque to build [up / down] inside your heart. This can lead to heart disease. He wrote: "Years of [extreme / extremely] exercise…appears to erase some benefits you get from [moderate / moderately] exercise, so that your risk of heart disease, of dying [of / for] coronary disease, is the same as an inactive person." The researchers looked [at / to] the health and training of 3,300 runners over the age of 35. Seventy per cent of [them / they] ran more than 30 kilometres a week. The study [found / find] that men who were marathon runners for 25 years had 62 per cent more plaque in their heart than men of the [similarity / same] age who did little or [no / not] exercise. Another doctor and long-time runner, John Hagan, said he feels [cheating / cheated] . He has been running marathons and [doing / having] triathlons since 1967. He used to run [down / up] to 60 kilometres per week. He said: "As a physician and a runner, I felt betrayed. I thought I was out there [exhausting / exhausted] myself, building an absolutely indestructible heart." Dr Hagan advised people to exercise regularly but not to [overdo / overdid] things.