Summer is well and truly here, and as the temperatures rise and the clouds clear it's tempting to get outside and enjoy the good weather. If you're a fan of keeping fit, you might start putting your running shoes on and try to get a good 5k in before dinner while making the most of the sunshine. We're certainly not going to tell you to stay indoors and avoid exercising in the beautiful summer sun. However, you should be careful. Running in excessive heat can be harmful to your health, and ...