Intervals???

I did some intervals yesterday. For the first time in a long time I went out with a heart rate monitor on. I used to use them back in the 1990s when Peter Keen made them popular with his coaching of Chris Boardman - levels 1,2,3,4 and all that. I grew to hate it. And it was so fiddly and it never picked up the signal correctly. So I was amazed with the HRM strap that came with the new Garmin - so light, easy to adjust, you wouldt know you had it on really. I rode up to Ponty and then up the climb/long drag past the poly as hard as possible, and then went round and did it again. It was good fun. I used to do it in 52x12 as one of those power climb intervals to develop your strength. And of course the chain gang used to go up there. I can remember going up there at around 28mph hanging on to the back of 2 others people and we never saw anyone else again. It wasnt that fast this time. The day after I went out on my 40 mile ride around the vale, which was meant to be more sedate. I took it easy. My average HR was about 139. Its interesting, I have no idea what my max would be these days - and have no desire to find out really - which means that these numbers are just numbers and dont really mean anything. But I am aware of the old 220 minus your age formula, and thats what worries me more...