I wrote recently on the need to physically test yourself from time to time to keep track of progress and evaluate your program.
The best and easiest way to measure your aerobic fitness would be to time yourself over the desired distance. For example a timed run over 5km.
Another factor which adds to interest is your heart rate. You maximum heart rate (MHR) is estimated to be 220 minus your age. Fro example a 40 year old would be 220-40=180. There is large variability between people however, and what is of real interest is the relative intensity at which you get close to your MHR, and how quickly it comes back down towards resting levels – the quicker the better. If you train with a friend this can be an interesting thing to compare as you warm down/stretch.
