This may be a "Yeah so" to everybody, but it has just occurred to me, and seems important.

The regime I work with uses Zones: warmup, moderate, aerobic etc.

I reckon any exercise is good exercise, but even walking at a fair clip (7-8 KMH) up hill and down dale, I struggle to get into the aerobic zone, and certainly not on average.

At this stage I am not getting into time in zones etc. I work with averages. This is partly because I have seen so many wildly variable maximum heart rates and zone numbers that I figure "wot the..." and partly because at this stage it's all just too finicky to interest me.

So I do a bike ride in the morning, say an hour with an average heart rate of 135, which is into my aerobic zone. Here, every minute is worth 3 points.

Then in the afternoon I do an hour of brisk walking over the same terrain, but my average will be about 110. Here every minute is worth 1 point.

If I leave my HRM with the morning session still on it, it makes it look as if my afternoon walk actually detracted from my points score. The average can drop down a zone, and although I have done more exercise, it looks like the reverse.

Just thought it was worth mentioning. I now record two separate sessions.