...and I am probably fitter than you. How? I skip. I started skipping a few weeks back and I can tell you it fcuking knackering. You think running is tiring, skipping is on my estimate 3 times as bad. Its a fantastic cardio workout and also seems to build muscular endurance. The first few times you do it your entire body will ache the next morning especially your calves and triceps but also strangely your abs. The other benifit is that its alot more fun and interesting than running, once you get the basics you can start alternating your rhythm and pace and start doing double jumps, (rope goes under twice per jump) triple jumps and if you are amazing quadruple jumps. And the proof? By replacing running with skipping for 3 weeks I have shaved 30 seconds of my 1 mile personal best (now 6:40). So if you are getting frustrated or bored with running go buy a skipping rope. Get a good one with a leather rope and ball bearings like boxers use and it will make life easier but I use a 7 quid nike one I got from JJB and its fine. J.