I"ve been using the Motion Traxx podcasts this week. There are loads to choose from but I've been doing the ones that build up from 150bpm to 170bpm over an hour. They're a bit like the stamina podcast but a bit longer - about an hour. The bloke who does the introduction is annoying but I found the gradual increase in bpm is anout right for me. My pace is getting a bit better/constant & having just done 7km I'm feeling ready for the rest of the day. on top of the running I've also swum 3km this week. Not bad for some who is 48 and 51 weeks old!