I'm planning to start couch to 5k this week and had intended that Ddog would come with me - she's a medium sized three year old cross. However, a friend said that while the early stages (where it's a mixture of walking and running) would be fine, dogs shouldn't run for any distance at a constant pace as it was bad for their heart - they are designed to sprint in short bursts. I know plenty of people who run far faster and further than I'm ever likely to go with their dogs but wondered if my friend was right? Ddog is slim and fit (unlike me) and a houndy sort of build.